Atmospheric Science Final Exam Review

Significance of observations in weather forecast

(1) Observations help us plan our day in terms of how to dress, whether we need to de-ice our windshields, whether we need to carry along an umbrella, etc. ; (2) Observations are critical for producing accurate weather forecasts. It would be difficult to make an accurate prognosis of future weather without a proper diagnosis of the current weather; (3) Observations are critical for assessing the accuracy of weather forecasts. If scientists altered some component of the computer code that generates forecasts, for example, it's important to know whether that alteration helped or hurt the accuracy of the forecast.

shortwave radiation vs longwave radiation

Earth radiates absorbed energy back in the form of longwave radiation. Sun emits shortwave energy because it has a lot of energy to give off.

Inversions layers and thunderstorms

Huge quantities of latent heat needed to sustain a supercell require special conditions that keep the lower troposphere warm and moisture rich. The existence of an inversion layer a few kilometers above the surface helps to provide this basic requirement.

Forecast accuracy

Initialization Use of appropriate grid resolution Model physics Sun-grid scale processes Numerics

Clouds

When the temperature in the atmosphere drops below the Due Point, water vapor condenses or freezes out forming the numerous water droplets and/or ice crystals making up clouds.

occluded front

a front where a warm air mass is caught between two colder air masses and brings cool temperatures and large amounts of rain and snow

warm front

a front where warm air moves over cold air and brings drizzly rain and then are followed by warm and clear weather

squall line

a narrow band of high winds and storms associated with a cold front. A Squall line is a relatively narrow band of thunderstorms, some of which may be severe, that develops in the warm sector of middle-latitude cyclone. Size >500 km in extent. Last 10 hours or more

Advection fog

created when warm, moist air from the sea blows onto cooler land surface

intentional weather modification

deliberate human intervention to influence atmospheric processes that constitute the weather

absolute humidity

mass of water vapor in a given volume of air

Measuring pressure

mercury barometer and aneroid barometer Measured in milibars

sublimation/deposition

occur at the boundary between the solid and gas phases.

major components of air pollution

particulates, carbon monoxide, sulfur oxides, nitrogen oxides, and hydrocarbons

Observed Distribution of Pressure and Winds

polar easterlies near canada (low on each side high above- subpolar low arrow downwards east to west) Westerlies over the US (upward west to east, highs over atlantic and pacific oceans - subtropical highs) Trades over Mexico (down east to west) Equatorial low Northern South America(trades upward east to west) Highs on both sides of South America- subtropical high Westerlies downward curve in southern South America Subpolar low in the south upwards flow from east to west

hail, rime

precipitation of ice pellets when there are strong rising air currents. pellets of frozen rain that fall in showers from cumulonimbus clouds.

Properties of water

readily converted to solid, liquid, or gas solid phase less dense than liquid phase high heat capacity- changing temperature requires considerable energy.

Scales of atmospheric motion (space vs. time)

small turbulent eddies - microscale 2m, secconds to minutes tstorms, tornadoes- microscale- mesoscale 20 km minutes to hours mountain valley breeze- mesoscale 20 km, hours to days Hurricanes, tropical storms- mesoscale- sypnotic scale 2000km days to weeks or more midlat. highs and lows wx fronts- sypnotic scale, days to weeks or more- long waves(global scalw- 5000km)

Changes of state of water

solid, liquid, gas

Condensation nuclei

tiny bits of particulate matter that serve as surfaces on which water vapor condenses

rain

water falling in drops from vapor condensed in the atmosphere.

N. American air masses

winter- cA- very cold, very dry Canada cP- cool, dry throughout northern US mP- cool, humid west coast and east coast mT- warm, humid in southern united states summer- same as winter, except cT- hot,dry around Arizona region.

Atmospheric Boundary Layer (ABL)

ABL experiences a daily cycle of all meteorological events. Exchanges information with the surface on short time scales. Close to surface, atmospheric flow becomes turbulent. - due to vertical wind shear (wind becomes 0 at the surface).

Montreal Protocol.

(1987) phase-out of ozone depleting substances

Global Distribution of Precipitation

(Top of globe to bottom) Polar high- sparse precipitation in all seasons Subpolar low- Ample precip. in all seasons winter wet, summer dry (northern hemisphere) Subtropical high- Dry in all seasons Equatorial- Abundant precipitation Summer wet, winter dry (southern hemisphere) Subtropical high- Dry in all seasons winter wet, summer dry Subpolar low- Ample precipitation in all seasons. Polar high- Sparse precipitation in all seasons

Stable boundary layer

- develops at night due to surface cooling (longwave cooling). Forms under residual layer.

Consequences of acid rain

-kills plants (forests) (soil) -aquatic life (fish) -damaged buildings and statues made of limestone (calcium carbonate) -damages metals (Bridges) -lowers pH of lakes

Stratosphere

2nd layer of atmosphere; extends from 10 to 30 miles up; location of ozone layer; absorbs 95% of Ultraviolet radiation; temperature increases with altitude increase.

stationary front

A boundary between air masses that don't move possibly causing rain for several days

Drylines

A boundary between humid air and denser dry air. A favored location for thunderstorm development.

Air mass thunderstorms, distribution of lightning

A number of mechanisms, such as unequal heating of Earth s surface or lifting of warm air along a front or mountain slope, can trigger the upward air movement needed to create thunderstorm-producing cumulonimbus clouds. At any give time there are about 2000 Thunderstorms in progress: 2,000 Thunderstorms at any given time 45,000 Thunderstorms per day 16 million per year Lightning strikes the Earth about 100 times per second.

Rain shadow desert

A rain shadow is a dry area on the leeward side of a mountainous area (away from the wind). The mountains block the passage of rain-producing weather systems and cast a "shadow" of dryness behind them. Wind and moist air is drawn by the prevailing winds towards the top of the mountains, where it condenses and precipitates before it crosses the top. The air, without much moisture left, advances across the mountains creating a drier side called the "rain shadow".

Fujita Scale

A scale that tells how severe a tornado is based on wind speed and the damage being caused. F0 < 73 Light damage. Some damage to chimneys; branches broken off trees; shallow-rooted trees pushed over; sign boards damaged. F1 73-112 Moderate damage. Peels surface off roofs; mobile homes pushed off foundations or overturned; moving autos blown off roads. F2 113-157 Considerable damage. Roofs torn off frame houses; mobile homes demolished; boxcars overturned; large trees snapped or uprooted; light-object missiles generated; cars lifted off ground. F3 158-206 Severe damage. Roofs and some walls torn off well-constructed houses; trains overturned; most trees in forest uprooted; heavy cars lifted off the ground and thrown. F4 207-260 Devastating damage. Well-constructed houses leveled; structures with weak foundations blown away some distance; cars thrown and large missiles generated. F5 261-318 Incredible damage. Strong frame houses leveled off foundations and swept away; automobile-sized missiles fly through the air in excess of 100 meters (109 yds); trees debarked; incredible phenomena will occur.

Mesoscale Convective Complex

A slow-moving roughly circular cluster of interacting thunderstorm cells covering an area of thousands of square kilometers that may persist for 12 hours or more. They form most frequently in the Great Plains from groups of afternoon airmass thunderstorms. Although MCCs sometimes produce severe weather, they also provide a significant portion of the growing-season rainfall to the agricultural regions of the central United States.

Profile of a hurricane, formation regions

A steep pressure gradient generates the rapid, inward spiraling winds of a hurricane. As the warm, moist air approaches the core of the storm, it turns upward and ascends in a ring of cumulonimbus towers and forms a doughnut-shaped wall called the eye wall. At the very center of the storm, called the eye, the air gradually descends, precipitation ceases, and winds subside. Most hurricanes form between the latitudes of 5 and 20 over all tropical oceans except the South Atlantic and eastern South Pacific. The North Pacific has the greatest number of storms, averaging 20 per year. In the western Pacific, hurricanes are called typhoons, and in the Indian ocean, they are referred to as cyclones.

geostrophic wind

A wind that moves parallel to the isobars as a result of the balance between the pressure gradient force and the Coriolis effect.

Life Cycle of a Mid-Latitude Cyclone, Clashing air masses

According to the Norwegian model, cyclones form along fronts and proceed through a generally predictable life cycle. • This cycle can last a few days to over a week. • First, cyclogenesis (cyclone formation) forms. Here two air masses of different densities are moving roughly parallel to the front, but in opposite direction. • Under suitable conditions the frontal surfaces will take a wave shape that is usually several hundred kilometers long. • These storms that intensify or deepen develop waves that change in shape over time, become a tall breaking wave As wave develops, warm air advances poleward invading the area formerly occupied by colder air, while cold air moves equatorward. • This change in the direction of surface flow is accompanied by a readjustment in the pressure pattern that results in nearly circular isobars, with the low pressure centered at the crest of the wave. • The resulting flow is a counterclockwise cyclonic circulation. • Once the cyclonic circulation develops, we generally see convergence to result in lifting. Usually, the position of the cold front advances faster than the warm front and begins to close (lift) the warm front. • This progress known as occlusion, forms an occluded front. • As occlusion begins, the storm often intensifies. Pressure at the storms center falls, and wind speeds increase. In the winter, heavy snowfalls and blizzardlike conditions are possible in this phase of storms evolution. • As more of the sloping discontinuity (front) is forced aloft, the pressure gradient weakens. In a day or two the entire warm sector is displaced and cold air surrounds the cyclone at low levels. • Thus, the horizontal density (temperature) difference that existed between the two contracting air masses has been eliminated.

Classifying air masses

Air masses are named for the latitude and the nature of the surface of the source region. The latitude of the source region indicates the temperature of the air mass. The three categories are: Arctic (A) Polar (P) Tropical (T) The nature of the surface of the source region indicated the moisture content of the air mass. The two categories are: Maritime (m) Continental (c) cP = Continental polar—very cold and very dry cA = Continental arctic—cold and dry cT = Continental tropic—warm and dry mA = Marine arctic—cold and wet mT = Marine tropic—warm and wet

Natural air pollution and some examples.

Air pollution can result from both human and natural actions. Natural events that pollute the air include forest fires, volcanic eruptions, wind erosion, pollen dispersal, evaporation of organic compounds and natural radioactivity.

Horizontal and vertical pressure variations

Air pressure decreases with altitude. Air pressure increases with depth.

Electric charging and lightning

All clouds are electrified to some degree. In vigorous convective clouds sufficient electrical charges are separated to produce electric fields that exceed the dielectric breakdown of cloudy air, resulting in intracloud lightening discharge. Most lightening occurs in cold clouds, although rarely with warm clouds.

Anticyclonic Weather and Blocking Highs

Anticyclones generally produce clear skies and calm conditions. • This does not imply, however, that anticyclones always bring desiable weather. • Anticyclones often brings record- breaking cold temperatures. • Approximately, one to three times each winter, large anticyclones form and persist over the middle latitudes for nearly two weeks and sometimes longer than a month. • These are sometimes called blocking highs. • Once in place these anticyclones block the eastward migration of cyclones. • They can also contribute to air pollution episodes.

Conservation of angular momentum

As air flows inwards toward the eye of the hurricane, its angular velocity increase due to conservation of angular momentum. Conservation of angular momentum states: radius1 X rotational velocity1 = radius2 X rotational velocity2

environmental lapse rate

As you go up, the temperature gets colder because you are moving away from source of heat (Earth)

Convergence

At the surface, low pressure systems have a counterclockwise rotation in the Northern Hemisphere, with the wind turning slightly inward towards the lowest pressure. This causes air to converge, or come together, at the center of the low near the ground. Since the converging air has nowhere else to go, it rises. As the air rises, the water vapor within cools and eventually condenses into cloud droplets and raindrops. Because of this, low pressure centers are generally associated with clouds, precipitation, and what we generally call "bad weather."

pressure vs. altitude

Atmospheric pressure drops as you increase in altitude; inverse.

Changes in abundance of CO2

Burning of fossil fuels (coal and oil). Photosynthesis requires an intake of CO2 reducing levels. Particulates such as sea salts from breaking waves, spider legs,and smoke and soot from fires (aerosols) act as surfaces on which water vapor may condense, a function in the formation of clouds and fog; also absorb or reflect incoming solar radiation.

hurricane warning

By contrast, a hurricane warning is issued when sustained winds of 119 kilometers per hour or higher are expected within a specified coastal area in 24 hours or less. Two important factors in the watch and warning decision process are (1) adequate lead time and (2) attempting to keep over-warning at a minimum.

Greenhouse gases, major and minor.

Carbon dioxide (CO2): Carbon dioxide enters the atmosphere through burning fossil fuels (coal, natural gas, and oil), solid waste, trees and wood products, and also as a result of certain chemical reactions (e.g., manufacture of cement). Carbon dioxide is removed from the atmosphere (or "sequestered") when it is absorbed by plants as part of the biological carbon cycle. Methane (CH4): Methane is emitted during the production and transport of coal, natural gas, and oil. Methane emissions also result from livestock and other agricultural practices and by the decay of organic waste in municipal solid waste landfills. Nitrous oxide (N2O): Nitrous oxide is emitted during agricultural and industrial activities, as well as during combustion of fossil fuels and solid waste. Fluorinated gases: Hydrofluorocarbons, perfluorocarbons, sulfur hexafluoride, and nitrogen trifluoride are synthetic, powerful greenhouse gases that are emitted from a variety of industrial processes. Fluorinated gases are sometimes used as substitutes for stratospheric ozone-depleting substances (e.g., chlorofluorocarbons, hydrochlorofluorocarbons, and halons). These gases are typically emitted in smaller quantities, but because they are potent greenhouse gases, they are sometimes referred to as High Global Warming Potential gases ("High GWP gases").

Saffir-Simpson scale

Classifies hurricanes according to wind speed, air pressure in the center, and potential for property damage. 1 74-95 mph 64-82 kt 119-153 km/h Very dangerous winds will produce some damage: Well-constructed frame homes could have damage to roof, shingles, vinyl siding and gutters. Large branches of trees will snap and shallowly rooted trees may be toppled. Extensive damage to power lines and poles likely will result in power outages that could last a few to several days. 2 96-110 mph 83-95 kt 154-177 km/h Extremely dangerous winds will cause extensive damage: Well-constructed frame homes could sustain major roof and siding damage. Many shallowly rooted trees will be snapped or uprooted and block numerous roads. Near-total power loss is expected with outages that could last from several days to weeks. 3 (major) 111-129 mph 96-112 kt 178-208 km/h Devastating damage will occur: Well-built framed homes may incur major damage or removal of roof decking and gable ends. Many trees will be snapped or uprooted, blocking numerous roads. Electricity and water will be unavailable for several days to weeks after the storm passes. 4 (major) 130-156 mph 113-136 kt 209-251 km/h Catastrophic damage will occur: Well-built framed homes can sustain severe damage with loss of most of the roof structure and/or some exterior walls. Most trees will be snapped or uprooted and power poles downed. Fallen trees and power poles will isolate residential areas. Power outages will last weeks to possibly months. Most of the area will be uninhabitable for weeks or months. 5 (major) 157 mph or higher 137 kt or higher 252 km/h or higher Catastrophic damage will occur: A high percentage of framed homes will be destroyed, with total roof failure and wall collapse. Fallen trees and power poles will isolate residential areas. Power outages will last for weeks to possibly months. Most of the area will be uninhabitable for weeks or months.

climate feedback

Climate feedbacks: processes that can either amplify or diminish the effects of climate forcings. A feedback that increases an initial warming is called a "positive feedback." A feedback that reduces an initial warming is a "negative feedback." Clouds. Clouds have an enormous impact on Earth's climate, reflecting about one third of the total amount of sunlight that hits the Earth's atmosphere back into space. Even small changes in cloud amount, location and type could have large consequences. A warmer climate could cause more water to be held in the atmosphere leading to an increase in cloudiness and altering the amount of sunlight that reaches the surface of the Earth. Less heat would get absorbed, which could slow the increased warming. Precipitation. Global climate models show that precipitation will generally increase due to the increased amount of water held in a warmer atmosphere, but not in all regions. Some regions will dry out instead. Changes in precipitation patterns, such as increased water availability, may cause an increase in plant growth, which in turn could potentially removing more carbon dioxide from the atmosphere. Greening of the forests. Natural processes, such as tree growth, remove about half of human carbon dioxide emissions from the atmosphere every year. Scientists are currently studying where this carbon dioxide goes. The delicate balance between the absorption and release of carbon dioxide by the oceans and the world's great forested regions is the subject of research by many scientists. There is some evidence that the ability of the oceans or forests to continue absorbing carbon dioxide may decline as the world warms, leading to faster accumulation in the atmosphere. Ice albedo. Ice is white and very reflective, in contrast to the ocean surface, which is dark and absorbs heat faster. As the atmosphere warms and sea ice melts, the darker ocean absorbs more heat, causes more ice to melt, and makes the Earth warmer overall. The ice-albedo feedback is a very strong positive feedback.

Climate dynamics: means, anomalies, and variability

Climate variability and predictability pose difficult mathematical, computational, and observational questions that have generated increased intellectual excitement in recent years. The answers to these questions have important ramifications for society, from planning for next year's electrical demand to answering complex questions involving long-term global change. While there are theoretical limits to predicting day-to-day weather, progress in predicting El Nino supports the idea that seasonal averages of temperature, rainfall, etc., may be at least partly predictable months or even years in advance.

Neutral boundary layer

Clouds and strong winds prevent strong daily cycle. Turbulent heat and moisture exchange at the surface is small. Acts as a friction layer.

Clouds influence on the atmosphere

Clouds cool Earth's surface by reflecting incoming sunlight. Clouds warm Earth's surface by absorbing heat emitted from the surface and re-radiating it back down toward the surface. Clouds warm or cool Earth's atmosphere by absorbing heat emitted from the surface and radiating it to space. Clouds warm and dry Earth's atmosphere and supply water to the surface by forming precipitation. Clouds are themselves created by the motions of the atmosphere that are caused by the warming or cooling of radiation and precipitation.

Cloud cover and albedo on temperature

Clouds lower surface temperature during the day, but increase temperatures at night. A high albedo reduces surface temperature. - Reflect back to space proportion of sunlight that strikes. Absorb outgoing radiation and emit a portion to Earths surface.

Traveling Cyclones: patterns of movement

Cyclone development does not occur uniformly over Earth, but tends to favor certain locations, such as the leeward sides of mountains and coastal regions. • In general, cyclones form in areas where large temperature contrasts occur in the lower troposphere. Once formed, cyclones tend to first travel in an easterly direction across North America and then follow a more northeasterly path into the North Atlantic. • However, numerous exceptions to this general trend occur. • Most pacific storms do not cross the Rockies intact, but they redevelop on the lee (eastward) side of these mountains. • The cyclones that form in Canada tend to move southeastward and then turn northeastward and move out into Atlantic. • Most of these storms traverse the Great Lakes region, making it the most storm-ridden portion of the country.

Temperature observations

Daily temperature is determined by averaging the 24 hourly readings or by adding maximum and minimum temps.and dividing by 2. Daily range computed from maximum and minimum. Monthly mean temperature by adding together daily means for each day and dividing by number of days in the month. Annual mean temp. is average of 12 monthly means. Annual temp. range computed by finding diff. of warmest and coolest monthly temperatures.

Hurricane damage

Damage caused by hurricanes can be divided into three categories: (1)storm surge, which is most intense on the right side of the eye where winds are blowing toward the shore, occurs when a dome of water sweeps across the coast near the point where the eye makes landfall, (2) wind damage, and (3) inland freshwater flooding, which is caused by torrential rains that accompany most hurricanes.

Influence of temperature on air pressure

Decreased velocity results in fewer collisions between molecules and air pressure decreases. Air density plays a role in the correlation between temperature and pressure because warmer air is less dense than cool air, allowing molecules to have more space to collide with greater force.

Radiation

Does not need a medium to transfer through like the other two mechanisms. Travels through vacuum of space, heat transfer where solar energy reaches the planet. All objects emit radiate energy of a range of wavelengths.

pressure gradient force

Drives air from areas of higher barometric pressure to areas of lower barometric pressure, causing winds.

CO2, temperature, and climate - ice ages.

Earth's climate has varied widely over its history, from ice ages characterised by large ice sheets covering many land areas, to warm periods with no ice at the poles. Several factors have affected past climate change, including solar variability, volcanic activity and changes in the composition of the atmosphere. Data from Antarctic ice cores reveals an interesting story for the past 400,000 years. During this period, CO2 and temperatures are closely correlated, which means they rise and fall together. However, based on Antarctic ice core data, changes in CO2 follow changes in temperatures by about 600 to 1000 years, as illustrated in Figure 1 below. This has led some to conclude that CO2 simply cannot be responsible for current global warming. This statement does not tell the whole story. The initial changes in temperature during this period are explained by changes in the Earth's orbit around the sun, which affects the amount of seasonal sunlight reaching the Earth's surface. In the case of warming, the lag between temperature and CO2 is explained as follows: as ocean temperatures rise, oceans release CO2 into the atmosphere. In turn, this release amplifies the warming trend, leading to yet more CO2 being released. In other words, increasing CO2 levels become both the cause and effect of further warming. This positive feedback is necessary to trigger the shifts between glacials and interglacials as the effect of orbital changes is too weak to cause such variation. Additional positive feedbacks which play an important role in this process include other greenhouse gases, and changes in ice sheet cover and vegetation patterns.

El Nino, La Nina

El Niño is a gradual warming of eastern Pacific waters in December or January. La Niña is the opposite of El Niño and refers to colder-than-normal ocean temperatures. Impact of El Niño: It is noted for its potentially catastrophic impact on weather and economies of Chile, Peru, Australia, and other countries. Arid areas can receive a lot of precipitation. A change in surface water temperature can kill fish. El Niño has been recognized as part of the global atmospheric circulation pattern. Impact of La Niña: La Niña is also an important atmospheric phenomenon. In the western Pacific, wetter than normal conditions occur. There are also more frequent hurricanes in Atlantic. Southern oscillation: This is the seesaw pattern of atmospheric pressure between the eastern and western Pacific. Winds are the link between pressure changes and the ocean warming and cooling associated with El Niño and La Niña.

Influence of water vapor on pressure

Evaporation depends on water temperature -- as water warms, more molecules evaporate from its surface. Water in cooler air evaporates less and water in warmer air evaporates more and faster -- hence the relationship between heat and humidity. ... Saturated vapor pressure rises with an increase in water vapor.

Examples of primary and secondary pollutants, and their sources.

Examples of primary pollutants include sulfur dioxide (SO2), carbon monoxide (CO), nitrogen oxides (NOX), and particulate matter (PM). Examples of secondary pollutants include photochemical oxidants (ozone, nitrogen dioxide, sulfur trioxide) and secondary particulate matter.

Temperature Scales

Fahrenheit, Celsius, Kelvin In Celsius scale, the interval is 100°, while the internal is 180° in the Fahrenheit scale. Therefore, a factor of 1.8 (i.e., 180/100) is used to convert temperature from one system to another °F = (1.8 X °C) + 32 °C = (°F - 32) / 1.8 Then, the absolute air temperature represents the degree of hotness of the air parcel relative to that at absolute zero at which molecular agitation will cease altogether. For this reason, the absolute temperature, expressed in Kelvin (K), is the most fundamental unit in which melting point of ice is set at 273 and the steam point at 373. Thus, unlike C and F scales, it is not possible to have a negative value when using the Kelvin scale. Thus, there is no temperature lower than absolute zero. °C = K 273 or K = °C + 273

upslope fog

Fog formed as moist, stable air flows upward over a topographic barrier

steam fog

Fog having the appearance of steam, produced by evaporation from a warm water surface into the cool air above.

Atmospheric ozone (O3) and its source, sinks, and role.

Fossil fuel combustion and the global manufacture of cement are responsible for more than 75% of human-caused CO2 emissions. Deforestation, changing agricultural practices and other land use changes are responsible for the rest. Note that the units are given in terms of the mass of carbon emitted as CO2 to distinguish it from carbon in other forms, such as soot. The combustion of fossil fuels produces CO2 with a different carbon-isotope signature than the CO2 present in the atmosphere before the Industrial Revolution. The CO2 from combustion has a lower 13CO2/12CO2 ratio. The 13CO2/12CO2 ratio of atmospheric CO2 has been dropping steadily as the concentration of CO2 has increased over the past half century. This change is strong evidence that human activity, the burning of fossil fuel, is the major cause of the increase in atmospheric CO2. Combustion requires and uses up oxygen from the atmosphere and precise measurements of the O2/N2 ratio in the atmosphere show that the fraction of oxygen is decreasing (measured in ppm relative to a standard sample). The land-based sink is largely the incorporation of CO2 into the products of photosynthesis by green plants. The oceanic sink includes photosynthesis by phytoplankton as well as dissolution, acid-base reactions, and carbonate-forming reactions of many marine organisms. CO2 is also released from the ocean as pH and temperature change, so the figure shows the net effect as both sink and source.

How winds generate vertical air motion

Friction Increased friction causes a drop in wind speed resulting in a pileup of air upstream from the ocean to land. Convergence can result in cloudy weather. Decreased friction causes and increase in wind speed from the land to the ocean. Subsidence and divergence results in clearing weather. Vertical airflow is associated with cyclones and anticyclones.

Heating the atmosphere

Gases that are the most effective absorbers of radiation that heat the atmosphere. - CO2 and water vapor absorb longwave radiation. - Greenhouse effect- Earths atmosphere trapping outgoing radiation.

rain gauge

Gauge consisting of an instrument to measure the quantity of precipitation

Evidences for climate change in Earth histroy: recent vs. long term change.

Global temperature rise warming oceans shrinking ice sheets glacial retreats sea level rise extreme events ocean acidity

Thunder and lightning

Ground Flashes that charge the ground negatively, originate in the lower part of the main negative charge center in the form of a discharge called a stepped leader which moves downward toward the Earth in discrete steps. Each step lasts for about 1 μs, during which time the stepped leader advances about 50m. The time interval between each step is about 50 μs. When the negatively charged leader is 10-100 m from the ground, a discharge moves upward from the ground to meet it. when contact is made, a large number of electrons flow downward and create a highly luminous lightning stroke. The lightning flash heats the air to above 30,000K. The pressure in the path increases to 10-100 atm, creating a powerful shockwave, and further out, a sound wave known as thunder.

Sizes of particles in condensation and precipitation

Growth from the vapor phase: condensation Growth by riming: hailstones Growth by aggregation (clusters)

Characteristics of high, medium, low altitude clouds

High clouds are above 6000 m. Middle clouds range between 2000-6000 m. Low clouds are at altitudes of less than 2000 m. Clouds of vertical development extend upward to span more than one height range. (cumulonimbus) High clouds: Cirrus Cirrostratus Cirrocumulus Middle clouds: Altocumulus Altostratus Low clouds: Stratus Stratocumulus Nimbostratus

Laws of radiation

Hotter objects radiate more total energy per unit than cooler ones. Hotter objects radiate more short wave radiation than cooler ones. Objects that are good absorbers of radiation are also good emitters.

Human impact on hurricane frequency and intensity

Human-made global warming creates conditions that increase the chances of extreme weather. In some ocean basins, the intensification of hurricanes over time has been linked to rising ocean temperatures. Sea levels are also rising as the oceans warm and seawater expands. This expansion, combined with the melting of land-based ice, has caused global average sea level to rise by roughly 7-8 inches since 1900—a trend that is expected to accelerate over coming decades. Higher sea levels give coastal storm surges a higher starting point when major storms approach and pile water up along the shore. The resulting storm surge reaches higher and penetrates further inland in low-lying areas. The risk is even greater if storms make landfall during high tides.

Energy vs. velocity vs. force of a wind

Hurricane Wind Strength Increases as the Square of the Velocity We show the relative force strengths associated with the velocities starting the various category storms, and with the very high velocity of Hurricane Irma. Force is generated by the change in momentum of the striking air in a unit time. The Force on a unit area is the momentum hitting it for density r and mass m, with velocity V, which is m X V in a unit time. But in a unit time, a horizontal column of length V, hits, with mass m = r X V. Substituting that for m gives F = r V^2. That is that the force per unit area or pressure is the density times the velocity squared. The relative situation is when a car is speeding through the air, the car hits the air, and the force of air friction goes as velocity squared.

Ice core data and indicators of long-term climate change

Ice contains dust from volcanic eruptions and desert windstorms, pollen, microbes, meteorites, small trapped bubbles of "fossil air" and even changes in the concentrations of Beryllium-10, indicating changes in the strength of solar radiation. Combined, all of these data provide scientists with a surprisingly detailed look at past seasons, and can be used to reconstruct an uninterrupted and detailed climate record extending over hundreds of thousands of years.

Atmospheric Stability: stable vs. unstable air

If a rising parcel of air is cooler than the surrounding atmosphere it will tend to sink back to its original position. This is because cool air is more dense or heavier than warmer air. This is referred to as stable air. If a rising parcel of air is warmer than the surrounding atmosphere it will continue to rise. This is because warm air is less dense or lighter than cool air. This is referred to as unstable air.

formation of acid rain

In most areas within several hundred kilometers of large centers of human activity, the pH value of precipitation is much lower than the usual value found in unpopulated areas. This acidic rain or snow, formed when sulfur and nitrogen oxides produced as by-products of combustion and industrial activity are converted into acids during complex atmospheric reactions, is called acid precipitation.

Upper Airflow and Weather Forecasting

In order to understand the development of thunderstorms or the formation and movement of mid-latitude cyclones, meteorologists must know what is occurring aloft as well as at the surface. • 850-mb occurs at about 1.5 km above sea level. In addition to serving as a proxy for the 850-mb map in areas of high elevation, the 700-mb map has other uses as well. • The 700-mb flow, which occurs about 3 km above sea level, serves as steering mechanism for air-mass thunderstorms. • Thus winds at this level are used to predict the movement of these weather producers. • One rule of thump is that when temperatures at the 700-mb level are 14 C or higher, thunderstorms will not develop. The 500-mb level is found about at 5.5 km above sea level. • Here about half of Earth s atmosphere is below and half is above. • Troughs indicate the presence of a storm at mid-tropospheric levels. • Whereas ridges are associated with calm weather. • To estimate the movement of surface cyclonic storms, which tend to travel in the direction of the flow at the 500-mb level but at roughly a quarter to half the speed, forecasters find it useful to rely on 500-mb maps. Two of the regularly generated upperlevel maps, the 300-mb and the 200- mb charts, represent zones near the top of the troposphere. • It is at this levels that the details of the polar jet stream can best be observed. • Because the jet stream is lower in winter and higher in summer, 300-mb maps are most useful during winter and early spring, whereas the 200-mb maps are best during the warm season. • Typically, supercells tend to develop near the jet stream. The wavy flow aloft governs to a large extent, the overall magnitude and distribution of weather disturbances observed in the mid-latitudes. • Thus, accurate forecasts depend on our ability to predict long- and short-term changes in the upperlevel flow.

Mixed ratio humidity

Mass of water vapor in a unit of air compared to the remaining mass of dry air.

Ocean currents impact on weather and climate

Large scale of transfer of heat in areas with excess to areas of a deficit. Transfer of heat by winds and ocean currents equalizes latitudinal energy imbalances.

Difference between LA and London smog

London smog: requires humid/foggy, stagnant air have lots of coal burning SO2 + H20 -> H2SO4 LA. smog: requires clear, sunny skies (since L.A. photochemical smog requires sunlight for at one of the key chemical reactions). NOx + ROG + sunlight --> O3 + NO2 **ROG are reactive organic gases from unburned gasoline **NOx are oxides of nitrogen

Temperature

Measure of average kinetic energy of atoms or molecules in a substance. increases- energy gained decreases- energy lost

Polar ice loss. Melting of floating ice.

Melting sea ice has no impact on sea level rise because it's already floating in the ocean." Like a glass of ice water. As it warms, the ice in the glass melts, but the total volume of water does not change. However, melting sea ice does contribute to climate change

Scales of Atmospheric Motion

Microscale winds: The circulation is small and chaotic. They can last from seconds to minutes. They can be simple gusts, downdrafts, and small vortices, such as dust devils. Mesoscale winds: They can last from minutes to hours. They are usually less than 100 km across. Some mesoscale winds (thunderstorms and tornadoes) also have a strong vertical component. Macroscale winds: These winds are the largest wind patterns. These planetary-scale patterns can remain unchanged for weeks at a time. Smaller macroscale circulation is called synoptic scale. These wind systems are about 1000 km in diameter. Smaller macroscale systems are tropical storms and hurricanes.

Mesoscale, microscale, macroscale (spatial size, timescale)

Microscale- 0-1 km, seconds to minutes Mesoscale- 1km- 1000km, Minutes- hours, hours to days Macroscale- 1000km- 40000km, Hours to days, days to weeks

Monsoons (Asian, N. American)

Monsoon refers to a seasonal reversal of winds. The Asian monsoon, which affects India and its surrounding areas, China, Korea, and Japan. The monsoon is driven by pressure differences. The North American monsoon occurs in the southwestern U.S. and northwestern Mexico. This monsoon is driven by the extreme temperatures, which generate a low-pressure center over Arizona and results in a circulation pattern that brings moist air from the Gulf of California and from the Gulf of Mexico, to a lesser degree.

Convection

Most of the heat that occurs in the atmosphere and ocean is carried convection. Heat transfer that involves movement or circulation of a substance takes place in fluids. ie. boiling water Most heat in the thermosphere acquired by radiation and conduction is transported by convection.

Local winds, mountain winds

Mountain regions display many interesting weather patterns. One example is the valley wind which originates on south-facing slopes (north-facing in the southern hemisphere). When the slopes and the neighbouring air are heated the density of the air decreases, and the air ascends towards the top following the surface of the slope. At night the wind direction is reversed, and turns into a downslope wind. If the valley floor is sloped, the air may move down or up the valley, as a canyon wind. Winds flowing down the leeward sides of mountains can be quite powerful: Examples are the Foehn in the Alps in Europe, the Chinook in the Rocky Mountains, and the Zonda in the Andes

Sun- Earth relationship - revolution

Movement of Earth in an elliptical orbit around the sun producing a year. (perihelion- closest in January, aphelion- furthest in July)

Types of climate variability

Natural Climate Variation: There are several natural causes that force climate to change across time and scale. It can be further drilled down into the following categories. Natural Forcings of the Climate System The Sun and the Global Energy Balance Radiative Forcing Greenhouse Effect Natural Variability of the Climate Externally and Internally Induced Climate Variability Feedback Global and Hemispherical Variability Regional Variability Human-induced Climate Variation: Human activities also influence the climate. The major human-induced causes include changes in greenhouse gas (GHG) concentrations, changes in aerosol levels, and changes in land use and land cover. Enhanced Greenhouse Effect

Changes in variability - e.g. increasing severity of storms. Why?

Natural climate variability refers to the variation in climate parameters caused by nonhuman forces. There are two types of natural variability: those external and internal to the climate system. Variations in the sun, volcanic eruptions, and changes in the orbit of the Earth around the sun exert an external control on climate variability. These processes are the driving force behind changes that occur over long time periods, such as oscillations between ice ages and interglacial periods. Natural variability is also influenced by processes internal to the climate system that arise, in part, from interactions between the atmosphere and ocean, such as those occurring in the tropical Pacific Ocean during an El Niño event. These changes occur over shorter time periods, from months to decades. In any given year, natural variability may cause the climate to be different than its long-term average.

Natural vs man-made greenhouse gasses

Natural- carbon dioxide, methane,water vapor, and nitrous oxide Manmade- CFC's, fossil feuls such as coal and oil. Burning of forest lands and mining/ coal burning - moving carbon to gaseous state.

What is numerical weather prediction?

Numerical Weather Prediction (NWP) is the technique used to forecast weather using numerical models designed to represent atmospheric processes. • NWP relies on the fact that the behavior of atmosphere is governed by a set of mathematical equations. • If we can solve these equations, we will have a description of the future state of the atmosphere.

Weather its effect on air pollution.

One concerns the influence that weather conditions have on the dilution and dispersal of air pollutants. The second connection is the reverse and deals with the effect that air pollution has on weather and climate (e.g. increasing CO2 and global warming.)

Divergence and convergence

One mechanism responsible for divergence aloft is a phenomenon known as speed divergence. • Wind speeds can change in the vicinity of the jet stream so that in high wind speed zone, air accelerates and stretches out (divergence), while in low wind speed zone, air pile-up (convergence). the flow aloft contributes to the formation and intensification of surface low and high pressure systems. • Areas of upper level convergence and divergence are located in the vicinity of jet stream, where dramatic changes in wind speeds cause air either to pile-up (convergence) or spread our (divergence). • Below regions of upper-level convergence are areas of high pressure (anticyclones), whereas upper-level divergence supports the formation and development of cyclonic systems (lows)

Collision-coalescense process

One theory explaining how the behavior of individual droplets in a cloud leads to the formation of precipitation is the collision-coalescence process. Droplets suspended in the air will interact with each other, either by colliding and bouncing off each other or by combining to form a larger droplet. Now that cloud droplets have formed, we will try to understand how they can grow to the size of a raindrop. One such way (although, as we will soon see, not the most important) is through collision and coalescence. Cloud droplets will be carried by air currents within the cloud, and if they bump into each other, it is called a collision. However, if they collide then stick together, that is called coalescence. Although this process is important, especially in the tropics and in increasing the size of raindrops, it falls short of being the primary mechanism for the formation of raindrops.

orographic lifting

Orographic lift occurs when an air mass is forced from a low elevation to a higher elevation as it moves over rising terrain. As the air mass gains altitude it quickly cools down adiabatically, which can raise the relative humidity to 100% and create clouds and, under the right conditions, precipitation.

What are the major chemical components of the atmosphere

Oxygen and nitrogen make up 99% of the air, while CO2 making up 400 ppm.

The ozone and its importance

Ozone is a form of oxygen concentrated in the stratosphere. It absorbs incoming solar ultraviolet radiation, shields from potentially harmful UV radiation.

Diurnal cycle of temperature

Pattern that occurs every 24 hours. Solar radiation heats the ground, but doesn't heat immediately due to lands high heat capacity. As ground warms so does air above, by conduction. Sun treks across sky, at high noon when it reaches its peak, sunlight is at its most concentrated strength. However, because the ground and air must first store heat before radiating it to surrounding areas, a maximum air temperature isn't yet reached. It actually lags this period of maximum solar heating by several hours. When the amount of incoming solar radiation equals the amount of outgoing radiation does the daily high temperature occur. (3-5 pm) After noon, the Sun begins its retreat across the sky. From now until sunset, the intensity of incoming solar radiation continually declines. When more heat energy is being lost to space than is incoming at the surface, a minimum temperature is reached.

What is photochemical smog? What causes it?

Photochemical smog, a noxious mixture of gases and particles, is produced when strong sunlight triggers photochemical reactions in the atmosphere. A major component of photochemical smog is ozone.

primary vs. secondary pollutants

Primary- harmful chemicals emitted directly into air from natural processes & human activities Secondary- primary pollutants react with one another and basic components in air to form different harmful chemicals

Radiation fog

Radiation fog is a very common type of fog throughout the United States. It is most prevalent during the fall and winter. It forms overnight as the air near the ground cools and stabilizes. When this cooling causes the air to reach saturation, fog will form.

Norwegian cyclone model

Refer to polar front theory

Incoming solar radiation

Reflection- Light bounces from an object at the same angle and intensity. Albedo- % of radiation reflected by an object. Scattering- Produces a large number of weaker rays traveling in different directions. Backscattering- Scattering backwards and forwards. Absorption- Amount of energy absorbed by an object depends on wavelength (intensity) of the radiation and the objects absorbtivity (brightness of an object) - good absorbers appear black in color. Earths surface is a good absorber, the atmosphere is not.

Why temperature vary

Seasonally, daily, hourly Controls of temperature- cloud albedo and cover, ocean currents, altitude, differential heating of land and water

Severe thunderstorms, roll clouds, meso-cyclones, wall clouds

Severe thunderstorms are capable of producing heavy downpours and flash flooding as well as strong, gusty straight-line winds. They are influenced by strong vertical wind shear—that is, changes in wind direction and/or speed between different heights, causing updrafts to become tilted. Downdrafts from the thunderstorm cells reach the surface and spread out to produce an advancing wedge of cold air, called a gust front, which may form a roll cloud as warm air is lifted along its leading edge. - rollclouds The vertical wind profile of cells may produce a mesocyclone, a column of cyclonically rotating air, within which tornadoes sometimes form. Supercells appear to form as unstable air erupts from below to form unusually large cumulonimbus clouds with concentrated, persistent updrafts. wall cloud- an area of rotating clouds that extends beneath a supercell thunderstorm and from which a funnel cloud may appear

What are the major components of numerical models?

Simulation domain and grid setting Initial conditions (initialization) Boundary Conditions Numerical models uses mathematical relationship based on physical principles Numerical methods are used to solve mathematical relationships Post processing

World Distribution of Temperature

Smaller temperature range at the equator. Larger temperature range at higher altitudes. Interiors of continents have a higher temperature range. Coastal regions have smaller temperature range.

Unequal temperature distribution

Solar heating of the Earth's surface is uneven due to the fact land heats faster than water causing air to warm and expand and rise over land surfaces, while it cools and sinks over the cooler water surfaces. Also varies with latitude, time of day, season. Creates winds and drives the ocean currents. - Transport heat from the poles in an unending attempt to balance energy inequalities.

Supercell - characteristics, esp. mammatus clouds

Some of the most dangerous weather is produced by a type of thunderstorm called a supercell, a single, very powerful thunderstorm cell that at times may extend to heights of 20 kilometers (65,000 feet) and persist for many hours. - These clouds may have diameters ranging between 20 and 50 km. The dark overcast of a mammatus sky, with its characteristic bulging pouches, sometimes precedes a squall line. These usually form after a supercell reaches its maximum size and intensity. overshooting top (hump on top) anvil- ledge that extends to right of overshooting top mammatus clouds underneath anvil virga- rain that doesnt hit ground to left of mammatus clouds wall clouds- area that extends under supercell tornado extends from wall cloud hail to right, rain to right of hail

Sun- Earth relationship - rotation

Spinning of Earth on its axis, resulting in day and night.

sprites, elves, blue jets

Sprites are luminous flashes that last from a few to a few hundred μs, and extend from 90 km altitude down to cloud tops and more than 40 km in the horizontal. Probably generated by an electric field pulse associated with a cloud lightning stroke. Elves are μ s -long luminous rings that are centered over a lightning stroke at about 90 km altitude. They are likely due to atmospheric heating from the electromagnetic pulse generated by the lightning stroke. Blue Jets are luminous cones that extend upward from the tops of thunderstorms and provide an electrical connection between the thunderstorm and ionosphere.

Tides and hurricanes

Storm Surge is a dome of water 65-80 km (40-50 miles) wide that sweeps across the coast near the point where the eye makes landfall. If all the wave activity were smoothed out, the storm surge would be the height of the water above normal tidal level.

Major types of clouds

Stratus- smooth layers of low clouds; Cumulus- turret-shaped tops, flat bottoms (large, white puffy clouds, cotton balls);Cirrus- feather-like clouds made of ice crystals (very thin, high clouds). Nimbus- clouds that have rain falling from them (storm clouds)

Subsisdence

Subsidence, in the Earth's atmosphere, is most commonly caused by a low temperature. As the air cools, it becomes denser and moves towards the ground, as warm air becomes less dense and moves upwards. Subsiding air, when cool, is subject to adiabatic warming, which tends to cause the evaporation of any clouds that might be present.

Surface winds vs. winds aloft

Surface winds travel at an angle across isobars, toward low pressure. Winds aloft: Curved airflow: Winds around cells of high pressure or low pressure follow curved paths. Gradient winds blow at a constant speed. They are parallel to the curved isobars. Centers of low pressure are called cyclonic; winds flow counter-clockwise in the Northern Hemisphere. A trough is the result of isobars curving to form elongated regions of low pressure. Centers of high pressure are anticyclonic; winds flow clockwise in the Southern Hemisphere. A ridge is the result of isobars curving to form elongated regions of high pressure. Buys Ballot's Law states that if you stand with the wind at your back, low pressure will be at your left, high pressure on the right.

Trends in air quality.

The Clean Air Act of 1970 mandated the setting of standards for four of the primary pollutants— particulates, sulfur dioxide, carbon monoxide, and nitrogen oxides— as well as the secondary pollutant ozone. In 2004, emissions of the five major primary pollutants in the United States were about 54 percent lower than 1970. In 1990 Congress passed the Clean Air Act Amendments, which further tightened controls on air quality. Regulations and standards regarding the provisions of the Clean Air Act Amendments of 1990 are periodically established and revised.

frontal wedge

The bottom edge of an approaching cold front that pushing under the warm air mass as the air rises, it cools and moisture condenses to produce clouds and precipitation.

Condensation

The change of state from a gas to a liquid

Global Winds and Ocean Currents

The Coriolis force deflects surface currents poleward, which form nearly circular patterns of ocean currents called gyres. The Gulf stream is strengthened by westerly winds and continues northeastward. Importance of ocean currents: Ocean currents have an important on climate, which helps maintain the Earth's heat balance. Cold currents offshore result in a dry climate. Warm offshore current produce a warm moist climate. Ocean currents and upwelling: Upwelling, a wind-induced vertical movement, is the rising of cold water from deeper layers to replace warmer surface water. It occurs where winds blow parallel to the coast toward the equator.

IPCC 2007 report summary

The IPCC's 2007 Fourth Assessment Report summarizes current and probable future global trends and represents the consensus of atmospheric scientists around the world.

Short and long range forecasts

The NWS issues a number of model generated forecasts for time spans ranging from a few hours to more than two weeks. • However, the accuracy of these forecasts diminishes considerably beyond seven days. • In addition, the Climate Prediction Center, a branch of the NWS, produces 30- and 90- day outlooks. • These are not weather forecasts. Instead they offer insights into whether it will be drier or wetter, and colder or warmer than normal. • Despite improved seasonal outlooks, the reliability of extended forecasts has been disappointing.

lifting condensation level

The altitude at which condensation begins (the temperature of the rising air parcel reaches the dew point temperature).

Humidity dependence upon temperature, mass of water vapor Saturation

The amount of water vapor in the air at any given time is usually less than that required to saturate the air. The relative humidity is the percent of saturation humidity, generally calculated in relation to saturated vapor density.

melting/freezing

The arrangement of molecules in water becomes less orderly as water melts and more orderly as water freezes. Energy used to melt doesn't require energy (latent heat).

climate

The average weather conditions in an area over a long period of time

characteristics of an air mass

The characteristics of an air mass are acquired inthe source region, which is the surface area over whichthe air mass originates. The ideal source region has auniform surface (all land or all water), a uniformtemperature, and is an area in which air stagnates toform high-pressure systems. The properties(temperature and moisture content) an air massacquires in its source region are dependent upon anumber of factors—the time of year (winter orsummer), the nature of the underlying surface (whetherland, water, or ice covered), and the length of time itremains over its source region.

Factors controlling present day climate

The climate of any particular place is influenced by a host of interacting factors. These include latitude, elevation, nearby water, ocean currents, topography, vegetation, and prevailing winds. The global climate system and any changes that occur within it also influence local climate.

Steps in the formation of precipitation

The collision-coalescence process (precipitation from warm clouds) occurs as copious rainfall associated with clouds located below the freezing level (called warm clouds), especially in the tropics. Small droplets hit other droplets and become larger. They collide with more droplets and their falling velocity increases.Growth from the vapor phase: condensation

Thunderstorms: three stages

The cumulus stage is dominated by rising currents of air (updrafts) and the formation of a towering cumulonimbus cloud. Falling precipitation within the cloud causes drag on the air and initiates a downdraft that is further aided by the influx of cool, dry air surrounding the cloud, a process termed entrainment. The beginning of the mature stage is marked by the downdraft leaving the base of the cloud and the release of precipitation. With gusty winds, lightning, heavy precipitation, and sometimes hail, the mature stage is the most active period of a thunderstorm. Marking the end of the storm, the dissipating stage is dominated by downdrafts and entrainment. Without a supply of moisture from updrafts, the cloud soon evaporates. Only 20% of the moisture leaves the could as precipitation

gradient wind

The curved airflow pattern around a pressure center resulting from a balance among pressure-gradient force, Coriolis force, and centrifugal force.

hydrologic cycle

The cycle through which water in the hydrosphere moves; includes such processes as evaporation, precipitation, and surface and groundwater runoff.

Conduction

The direct transfer of heat from one substance to another substance that it is touching. Least signifigant way of transferring heat. Familiar through everyday life- metals good conductors, air and snow not.

Heat

The energy transferred between objects that are at different temperatures. latent heat - energy absorbed with no increase in temperature sensible heat- can feel or measure (senses)

Global circulation - three cell system

The global circulation can be described as the world-wide system of winds by which the necessary transport of heat from tropical to polar latitudes is accomplished. In each hemisphere there are three cells (Hadley cell, Ferrel cell and Polar cell) in which air circulates through the entire depth of the troposphere. Warm air rises at the equator (Hadley cell). As the flow moves poleward, it begins to cool and sinks at 20°-35° latitude. Trade winds meet at the equator, in a region with a weak pressure gradient, called the doldrums. The westerly circulation of surface winds (prevailing westerlies) between 30°-60° latitude is called the Ferrel cell. Circulation (at 60°-90°) within a polar cell produces polar easterlies; surface flows that move toward the equator.

The greenhouse effect and climate, global warming

The greenhouse effect is a natural process that warms the Earth's surface. When the Sun's energy reaches the Earth's atmosphere, some of it is reflected back to space and the rest is absorbed and re-radiated by greenhouse gases. Greenhouse gases include water vapour, carbon dioxide, methane, nitrous oxide, ozone and some artificial chemicals such as chlorofluorocarbons (CFCs). The absorbed energy warms the atmosphere and the surface of the Earth. This process maintains the Earth's temperature at around 33 degrees Celsius warmer than it would otherwise be, allowing life on Earth to exist. Enhanced greenhouse effect The problem we now face is that human activities - particularly burning fossil fuels (coal, oil and natural gas), agriculture and land clearing - are increasing the concentrations of greenhouse gases. This is the enhanced greenhouse effect, which is contributing to warming of the Earth.

Troposphere

The lowest layer of the atmosphere, in which temperature decreases at a constant rate as altitude increases. Most weather events occur and where humans live. Also, 80% of the Earth's mass - exchanges chemicals with land and oceans.

Major source regions of air masses

The main source regions are the high pressure belts in the sub tropics (giving rise to tropical air masses) and around the poles (the source for polar air masses). Warm source regions (tropical air masses): Sahara Desert - warm and dry Tropical Oceans - warm and moist Cold source regions (polar air masses): Arctic Ocean - cold and moist Siberia - cold and dry Northern Canada - cold and dry Southern Ocean - cold and moist The Gulf of Mexico and Caribbean Sea yield warm air masses. • In contrast, the snow and ice covered areas and adjacent ocean yield cold air masses. • The size and intensity of the source regions change seasonally . • No major source regions in the middle latitudes. • The middle latitudes are the site where cold and warm air masses clash, one of the stormiest region on the planet.

Water distribution on the earth

The majority of water, 97%, on Earth is salt water. Most all of the Earth's fresh water is frozen ice caps at the North and South poles.

conveyor belt model

The modern description of air flow through midlatitude cyclones. The Conveyer Belt Model consists of three interacting airstreams; - Two that originate near the surface and ascend - And the third that originates in the uppermost troposphere. It also accounts for distribution of precipitation and comma-shaped cloud pattern characteristic of mature cyclonic storms. The Warm Conveyer Belt carries warm, moist air from the Gulf of Mexico. • As it flows northward, convergence causes it to slowly ascend. • During its ascent, the warm, humid air cools adiabatically and produces a wide band of clouds and precipitation. • Depending on atmospheric conditions, drizzle, rain, freezing rain, and snow are possible. • When this air stream reaches the middle troposphere, it begins to turn right (eastward) and eventually joints general west-to- east flow aloft The Cold Conveyer Belt is airflow that starts at the surface ahead (north of) of the warm front and flows westward toward the center of the cyclone. • Flowing beneath the warm conveyor belt, this air is moistened by the evaporation of raindrops falling through it. • This belt also feeds significant (maritime) moisture into the storm. • Convergence causes this air stream to rise as it nears the center of the cyclone. • During its ascent, this air becomes saturated and contributes to the cyclone's precipitation. Upon reaching the middle troposphere, some of the flow rotates cyclonically around the low to produce the distinctive comma head of the mature storm system. • The remaining flow turns right (clockwise) and becomes incorporated into the general westerly flow. • Here it parallels the flow of the warm conveyor belt and may generate precipitation. Whereas the warm and cold conveyor belts begin at the surface, the dry air stream (dry conveyor belt) originates in the uppermost troposphere. • The dry conveyor belt is relatively cold and dry. • As this air stream enters the cyclone, it splits. • One branch descends behind the cold front. • The result is the clear, cool conditions normally associated with the passage of a cold front. In addition, this flow maintains the strong temperature contrast observed across the cold front. • The other branch of the dry conveyor belt maintains its westerly flow and forms the dry slot that separates the head and tail of a comma cloud pattern.

Ocean conveyor belt and energy transfer

The ocean is not a still body of water. There is constant motion in the ocean in the form of a global ocean conveyor belt. This motion is caused by a combination of thermohaline currents (thermo = temperature; haline = salinity) in the deep ocean and wind-driven currents on the surface. Cold, salty water is dense and sinks to the bottom of the ocean while warm water is less dense and remains on the surface. The ocean conveyor gets its "start" in the Norwegian Sea, where warm water from the Gulf Stream heats the atmosphere in the cold northern latitudes. This loss of heat to the atmosphere makes the water cooler and denser, causing it to sink to the bottom of the ocean. As more warm water is transported north, the cooler water sinks and moves south to make room for the incoming warm water. This cold bottom water flows south of the equator all the way down to Antarctica. Eventually, the cold bottom waters returns to the surface through mixing and wind-driven upwelling, continuing the conveyor belt that encircles the globe.

Positive vs. negative influence of ozone.

The ozone layer in the atmosphere (stratospheric ozone) is vital for protecting life on Earth from the Sun's damaging UV rays and regulating the climate on Earth. Without it, most people would be able to get a sunburn in a very short amount of time and genetic mutations causing skin cancer would be very common. Having ozone ( O 3 ) in the troposphere (the layer of the atmosphere we live in) can be damaging to vegetation and respiratory systems of many mammals. Additionally ozone is a main contributor to smog found in dense urban areas.

relative humidity

The percentage of water vapor in the air compared to the maximum amount of water vapor that air can contain at a particular temperature

Saturation vapor pressure, dependence upon temperature

The saturation vapor pressure is the pressure of a vapor when it is in equilibrium with the liquid phase. It is solely dependent on the temperature. As temperature rises the saturation vapor pressure rises as well.

fog and cloud dispersal

The techniques of cloud seeding can also be used for a second purpose, the removal of clouds and fog. This goal is desirable, as an example, in regions around an airport where prolonged fog can bring air travel to a halt, at great economic cost. The use of dry ice as a seeding agent can cause water droplets in fog to condense on ice crystals, after which they precipitate out of the air. In the process, fog banks and clouds may disappear.

Ozone layer and human influences. Ozone hole.

The term 'ozone hole' refers to the depletion of the protective ozone layer in the upper atmosphere (stratosphere) over Earth's polar regions. People, plants, and animals living under the ozone hole are harmed by the solar radiation now reaching the Earth's surface—where it causes health problems, from eye damage to skin cancer.

Mid-latitude cyclones, tornadoes, hurricanes

The term cyclone simply refers to the circulation around any lowpressure center, no matter how large or intense it is. Although tornadoes and hurricanes are, in fact, cyclones, the vast majority of cyclones are not hurricanes or tornadoes. Length Scales: Mid-latitude Cyclones ~ 1600 kilometers Hurricanes ~ 600 km Tornadoes ~ 0.25 km Thunderstorms, storms containing lightning and thunder, are related in some manner to tornadoes, hurricanes, and midlatitude cyclones. A thunderstorm is simply a storm that generates lightning and thunder. Thunderstorms form when warm, humid air rises in an unstable environment

Purpose of numerical models

The ultimate goal is to understand and accurately forecast the behavior of the atmospheric system The purpose of any model is to represent as accurately as possible the system of interest

Thermosphere

The uppermost layer of the atmosphere, in which temperature increases as altitude increases due to shortwave, high energy solar radiation by atoms of nitrogen and oxygen. No well defined upper limit.

Sea level rise - thermal expansion vs. rainoff

Thermal Expansion: When water heats up, it expands. About half of the past century's rise in sea level is attributable to warmer oceans simply occupying more space. Melting Glaciers and Polar Ice Caps: Large ice formations, like glaciers and the polar ice caps, naturally melt back a bit each summer. In the winter, snows, primarily from evaporated seawater, are generally sufficient to balance out the melting. Recently, though, persistently higher temperatures caused by global warming have led to greater-than-average summer melting as well as diminished snowfall due to later winters and earlier springs. This imbalance results in a significant net gain in the ratio of runoff to ocean evaporation, causing sea levels to rise. Ice Loss from Greenland and West Antarctica: As with the glaciers and ice caps, increased heat is causing the massive ice sheets that cover Greenland and Antarctica to melt at an accelerated pace. Scientists also believe meltwater from above and seawater from below is seeping beneath Greenland's and West Antarctica's ice sheets, effectively lubricating ice streams and causing them to move more quickly into the sea. Higher sea temperatures are causing the massive ice shelves that extend out from Antarctica to melt from below, weaken, and break off.

Mesosphere

Third layer of the atmosphere, temperatures decrease with height (coldest layer). 30 - 50 miles in altitude. The highest layer of the atmosphere in which gases are all mixed up rather than being layered by their mass.

Synoptic weather maps

This step is accomplished by placing the information on a number of synoptic weather maps. • They are called synoptic, which means coincident in time because they display a synopsis of the weather conditions at a given moment.

Triggering tropical depressions

Tropical disturbances that produce many of the strongest hurricanes that enter the western North Atlantic and threaten North America often begin as large undulations or ripples in the trade winds known as easterly waves.

What is weather analysis

This task is called weather analysis and involves collecting, transmitting and compiling millions of pieces of observational data. • Because the atmosphere is ever changing, this job must be accomplished quickly. • Supercomputers have greatly aided the weather analyst Lines and symbols are used to depict the weather patterns. • Once a map is generated an analyst fine-tunes it, correcting any errors or omissions. • In addition to the surface map, twice daily upper-air charts are drawn at 850-, 700-, 500-, 300- and 200- mb levels. • This series of upper-air charts provides a 3D view of the atmosphere.

Tornadoes: Formation and characteristics

Tornadoes form in association with severe thunderstorms that produce high winds, heavy rainfall, and often damaging hail. ü They form in any situation that produces severe weather including cold fronts, squall lines, and tropical hurricanes. ü Fortunately, less than 1% of all thunderstorms produce tornadoes. Tornadoes, sometimes called twisters, or cyclones, are violent windstorms that take the form of a rotating column of air, or vortex, that extends downward from a cumulonimbus cloud. Some tornadoes consist of a single vortex. Pressure within some tornadoes is 10% lower than outside the storm Air near the ground rushes into the tornado from all directions air streams are spiraled upward around the core until it eventually merges with the airflow of the parent storm. An important precondition linked to tornado formation in severe thunderstorms is the development of a mesocyclone that forms in the updraft of the thunderstorm. As the narrowing column of rotating air stretches downward, a rapidly spinning funnel cloud may emerge from a slowly rotating wall cloud. Tornadoes can form in association with severe weather, including Cold fronts Squall lines Hurricanes Most intense tornadoes are those that form in association with supercells. An important precondition linked to tornado formation is the development of a mesocyclone The formation of a mesoscyclone does not necessarily mean that tornado formation will follow, only about half of all mesocyclones produce tornadoes

Vertical Temperature Profile

Troposphere: -50 degrees - 0 degrees C (line extends from 0 to the dashed line of 20 km above -50). Stratosphere: -50 degrees - 0 degrees C(curves back opposite way of what it did in the troposphere. Mesosphere: 0 degrees- -80 degrees C ( curves from 0 as a continuation of stratosphere, but then curves to -80 degrees touching 80 km where the thermosphere starts. Thermosphere: -80 - no end C ( curves as a continuation of the mesosphere, but extends endlessly towards 80 degrees.

Transpiration, evaporation

Two ways water can enter the atmosphere as water vapor. Transpiration- evaporation of water from plant leaves.

Cross section of a hurricane

Vertical cross section of the hurricane circulation at low-levels, air flows cyclonically into the center of the storm. diverging, anticyclonic motion at tropopause level rising motion occurs in the eyewall, thunderstorms adjacent to the eye. subsidence on outer edge of storm rain bands sinking motion in the eye

Dry vs. wet lapse rate

Water vapor in a rising parcel of air will condense when the air becomes cold enough. The phase change from gas to liquid takes a little work from the water molecules. As they are working, they release heat. The heat decreases the cooling that occurs in the air parcel. Therefore, a rising parcel of dry air cools faster than a moist parcel of air. And conversely, a sinking parcel of dry air warms faster than a sinking parcel of moist air.

Difference between weather and climate

Weather is constantly changing it is the atmosphere at a given place or time while climate is the average generalization of the variations of the atmosphere over long periods of time. What you get vs what you expect. * Are expressed in the same elements of air pressure,type and amount of clouds and precipitation, temperature, etc.

weather radar

Weather radar, also called weather surveillance radar and Doppler weather radar, is a type of radar used to locate precipitation, calculate its motion, and estimate its type.

Westerlies, Jet Streams

Westerlies flow in wavy paths that have long wavelengths. The longest wave patterns are known as Rossby waves, which usually consist of 4-6 waves that encircle the globe. Rossby waves can have a large impact on weather. Jet streams: Embedded in westerlies Widths vary from less than 100 km to more than 500 km. Speeds can attain 100-400 kph. Polar and subtropical The polar jet stream is the most prevalent. It occurs along a major frontal zone, the polar front. The jet stream moves faster in winter. During the winter, occasionally it moves north-south. The subtropical jet stream is a semipermanent jet stream over the subtropics. It is a west-to-east current, centered at 25° N and S. It is mainly a winter phenomenon. The subtropical jet stream is slower than the polar.

Tree rings, recent climate, and the "hockey stick"

What evidence is there for the hockey stick? Link to this page What the science says... Since the hockey stick paper in 1998, there have been a number of proxy studies analysing a variety of different sources including corals, stalagmites, tree rings, boreholes and ice cores. They all confirm the original hockey stick conclusion: the 20th century is the warmest in the last 1000 years and that warming was most dramatic after 1920. Climate Myth... Hockey stick is broken "In 2003 Professor McKitrick teamed with a Canadian engineer, Steve McIntyre, in attempting to replicate the chart and finally debunked it as statistical nonsense. They revealed how the chart was derived from "collation errors, unjustified truncation or extrapolation of source data, obsolete data, incorrect principal component calculations, geographical mislocations and other serious defects" -- substantially affecting the temperature index." (John McLaughlin) The "hockey stick" describes a reconstruction of past temperature over the past 1000 to 2000 years using tree-rings, ice cores, coral and other records that act as proxies for temperature (Mann 1999). The reconstruction found that global temperature gradually cooled over the last 1000 years with a sharp upturn in the 20th Century. The principal result from the hockey stick is that global temperatures over the last few decades are the warmest in the last 1000 years.

Dew, white frost

When temperatures drop below freezing and the temperature reaches the dew or frost point, the ice on the ground is termed frost or frozen dew. "Frost" can form in two ways: Either by deposition or freezing. Depositional frost is also known as white frost or hoar frost. It occurs when the dewpoint (now called the frost point) is below freezing. When this frost forms the water vapor goes directly to the solid state. Depositional frost covers the vegetation, cars, etc. with ice crystal patterns (treelike branching pattern). If the depositional frost is thick enough, it resembles a light snowfall.

Sun- Earth relationship - Seasons

When the northern axis is pointing to the direction of the Sun, it will be winter in the southern hemisphere and summer in the northern hemisphere. Northern hemisphere will experience summer because the Sun"s ray reached that part of the surface directly and more concentrated hence enabling that area to heat up more quickly. The southern hemisphere will receive the same amount of light ray at a more glancing angle, hence spreading out the light ray therefore is less concentrated and colder. The converse holds true when the Earth southern axis is pointing towards the Sun.

Cyclone Formation, cyclonic and anticyclonic

Whenever the winds aloft exhibit a relatively straight zonal flow - that is from west to east - little cyclonic activity occurs at the surface. • However, when the upper air begins to meander widely from north -to south, forming high amplitude waves of alternating troughs (lows) and ridges (highs), cyclonic activity intensifies. • Moreover, when surface cyclones form, almost invariably they are centered below the jet stream axis and downwind from an upper level through. Airflow about a surface low is inward, a fact that leads to mass convergence. • Since cyclones exist for a week, surface convergence must be offset by outflow aloft. • As long as divergence aloft is equal to or greater than the surface inflow, the low pressure can be sustained. Both cyclones and anticyclones are related to each other. • The surface air that feeds a cyclone, for example, generally originates as air flowing out of an anticyclone. • Consequently, cyclones and anticyclones are typically found adjacent to one another. • Like cyclone, an anticyclone also depends on the flow aloft to maintain its circulation. • In the anticyclone, divergence at the surface is balanced by convergence aloft and general subsidence of the air column.

frost prevention

Wind machines to mix warmer air aloft with cooler surface air. Sprinklers distribute water which releases heat as it freezes. The ice covering also produces a thermal buffer with the surrounding air.

Local Winds

Winds that blow over short distances caused by unequal heating of Earth's surface within a small area. Chinook, country breezes

air mass

a body of air with horizontally uniform temperature, humidity, and pressure.

What is a weather forecast

a prediction of what the weather will be like for the next few days. a weather forecast is a scientific estimate of the weather conditions at some future time. • Forecasts are usually expressed in terms of the most significant weather variables, which include temperature, cloudiness, humidity, precipitation, wind speed and direction.

Bergeron Process

a process that produces percipitation; the process involves tiny ice crystals in a supercooled cloud growing larger at the expense of the surrounding liquid droplets. - the saturation vapor pressure with respect to ice is less than the saturation vapor pressure with respect to water. Ice crystals grow at the expense of water droplets These ice crystals begin to fall Falling ice crystals intercept clouds drops that collect and freeze on them. Sometimes these growing crystals fragment, multiplying the number of crystals. The resulting chain reaction rapidly produces many snow crystals, which by accretion, will produce snowflakes.

snow

a solid form of precipitation composed of ice crystals in complex hexagonal form.

Doppler radar

a specialized type of radar that can detect precipitation as well as the movement of small particles, which can be used to approximate wind speed

Microburst

a sudden, powerful, localized air current, especially a downdraft. Beneath storms, 4km across These straight-line concentrated bursts of wind are often caused when downdrafts are accelerated by rapid evaporative cooling. They typically last 2 to 5 minutes They can produce winds in excess of 100 miles/h

What is ensemble forecasting

a technique used for forecasting that produces multiple forecasts using the same model with slightly different initial conditions

Polar Front Theory

a theory that explains the life cycle of mid-latitude cyclones and their associated fronts. mid -latitude cyclones develop in conjunction with the polar front. • Remember, that the polar front separates cold polar air from warm subtropical air. • During the cool months, the polar front is generally well defined and forms a nearly continuous band around Earth. • It is along frontal zones where cold, equatorward moving air collides with warm, poleward moving air that most middle latitude cyclones form. • Since fronts play an important role in mid latitude cyclone developments, let us first consider the nature of fronts.

Types of precipitation in a thunderstorm

above 10km, 250 mb, -40C- ice between 500-250 mb, 5-10 km, 0- -40C- snow below 5km, above 600mb, above 0C- rain

Tornado Alley

an area of the Great Plains centered on eastern Kansas and Oklahoma and including parts of the surrounding states, where tornadoes are frequent.

major components of the climate system

an interactive system consisting of five major components: the atmosphere, the hydrosphere, the cryosphere, the land surface and the biosphere, forced or influenced by various external forcing mechanisms, the most important of which is the Sun

Hydrogen bonding in water

attractive forces that exist between hydrogen atoms in one water molecule and oxygen in any other water molecule. Electrons of the hydrogen atoms are strongly attracted to the oxygen atom. Therefore, the part of the water molecule containing the oxygen atom has a slightly negative charge, and the part containing hydrogen atoms has a slightly positive charge.

sleet, glaze

clear ice pellets precipitation, forms when rain falls through layer of freezing air.

Mechanisms of heat transfer

conduction, convection, radiation can all operate simultaneously, transfer heat between the sun and earth and between earth's surface, atmosphere, and outer space.

Hadley Cell - tropical circulation

consists of a single wind system in each hemisphere, with westward and equatorward flow near the surface and eastward and poleward flow at higher altitudes. The tropical regions receive more heat from solar radiation than they radiate back into space, and the polar regions radiate more than they receive; because both areas have nearly constant temperatures, Hadley theorized that warm air must therefore rise near the Equator, flow poleward at high altitudes, and lose heat to the cold air present near the poles. This cooler and denser air then descends and flows equatorward at low levels until it nears the Equator, where it is warmed and rises again.

unstable boundary layer

convective boundary layer- buoyancy-driven heat and moisture exchange in statically unstable conditions, caused by absorption of radiation or by advection of cold air over a warm surface.

Coriolis Force

effect whereby a mass moving in a rotating system experiences a force (the Coriolis force ) acting perpendicular to the direction of motion and to the axis of rotation. On the earth, the effect tends to deflect moving objects to the right in the northern hemisphere and to the left in the southern and is important in the formation of cyclonic weather systems.

global electric circuit

electrosphere- fair weather current (+) - earth surface (+ and -) thunderstorm (+) at top gives off ionic current (+) to electrosphere lightning (-) precipitation (+)

Frontal fog

fog formed when rain evaporates as it falls through a layer of cool air

cold front

forms when cold air moves under warm air which is less dense and pushes air up (produces thunderstorms heavy rain or snow

major causes of climate change

greenhouse gasses global warming rising emissions

latent heat

heat absorbed or radiated during a change of phase at a constant temperature and pressure.

absolute stability

if the environmental lapse rate is less than the moist adiabatic lapse rate, then it is also less than the dry adiabatic lapse rate, and it doesn't matter whether the air is saturated or not—we say that the air is absolutely stable:

Incoming solar and outgoing IR radiation vs. latitude

incoming- 250 w/msqr at 0 degrees lat.- extends to 50W/ms at 80degN outgoing- 300w/ms mostly constant until about 40-80N slight decrease to 150w/ms

The last 10,000 years and climate proxies

temperature over the last 10000 years is estimated by the use of proxies, thermometers were not developed or available until the 17th century. A typical proxy would be the examination of tree rings, the wider the ring, the warmer the Earth's temperature that year (or rather than local climate was warmer ). Other proxies would be ice cores from polar ice sheets, and corals from the oceans.

Heat budget

the annual balance of incoming and outgoing radiation to keep the Earth's temperature relatively constant. Energy balance is not maintained at each altitude.

hydrostatic balance

the balance between vertical pressure gradient force and gravity

Energy

the capacity to do work kinetic energy- object in motion: faster motion, greater the energy potential energy- object capable of motion or work

conditional instability

the condition of moist air with an environmental lapse rate between the dry and wet adiabatic rates. Conditionally unstable when it is stable with respect to an unsaturated parcel of air, but unstable with respect to a saturated parcel of air. -associated with warm, humid air. Unstable air is lifted (usually along a front) above condensation level resulting in storms and tornadoes.

air pollution

the contamination of air by harmful substances including gases and smoke

Idealized weather of a Mid-Latitude Cyclone

the distribution of clouds (i.e., comma shape) and thus the regions of possible precipitation. • Guided by the westerlies aloft, cyclones generally move eastward across the US. • We expect the first signs of cyclones arrival to appear in the western sky. • Later, in the Mississippi Valley, cyclones begin a more northeasterly trajectory. • Typically, they require two or four days to pass completely over a region. • During that period, abrupt changes in atmospheric conditions may occur.

Air mass modification

the exchange of heat or moisture with the surface over which an air mass travels When an air mass is colder than the surface over which it is passing, k is added after the air-mass symbol. • When an air mass is warmer than the surface over which it is passing, w is added after the air-mass symbol. • Therefore, k and w designation gives an indication of the stability of an air mass and hence the weather that might be expected. • For example, k air mass is often characterized by cumulus clouds. • In addition, upward and downward movements induced by cyclones and anticyclones or topography can also affect the stability of an air mass (mechanical or dynamic modifications).

Friction Force (Ff)

the force exerted by a surface as an object moves across it or makes an effort to move across it Friction significantly influences airflow near Earth's surface, but its effect is negligible at higher altitudes.

cloud seeding

the process of introducing freezing nuclei or condensation nuclei into a cloud in order to cause rain to fall

Adiabatic lapse rate

the rate at which the temperature of a parcel of air changes as the air rises or sinks.

dew point

the temperature at which the water vapor in the air becomes saturated and condensation begins.