Fundamentals of Weather

Average temperature profile of the Earth's atmosphere

(1) troposphere, tropopause (2) stratosphere, stratopause (3) mesosphere, mesopause (4) thermosphere

Stages of development of tropical system formation

(1) A tropical disturbance shows up as a mass of thunderstorms (2) The tropical disturbance becomes a tropical depression when winds increase in speed and many closed isobars appear (3) When isobars are close together and winds are between 35 and 64 knots, it is now a tropical storm and is given a name. (4) The tropical storm is classified as a hurricane after its winds pass 64 knots

Disadvantages of Polar Orbiting Satellites

(1) Cannot provide continuous viewing of one location

Types of Weather Fronts

(1) Cold fronts (2) warm fronts (3) stationary fronts (4) occluded fronts.

Types of Air Masses

(1) Continental Polar (2) Continental Arctic (3) Maritime Polar (4) Maritime Tropical (5) Continental Tropical

Three stages of an ordinary (air-mass) thunderstorm.

(1) Cumulus (2) Mature (3) Dissipating

Disadvantages of Geostationary Orbits

(1) Due to the high orbit, the spatial resolution of the data is not as great as for the polar orbiting satellites. (2) Poor spatial resolution in the polar regions (parallax). We will talk more about this later.

Midlatitude Cyclones

(1) Form by the energy of horizontal temperature differences (2) Cold-core lows: they have intensified lows above. (3) Midlatitudes have centers of rising air. (4) Strongest winds aloft in the jet stream (5) Linear isobars, with low pressure troughs

What are the different factors influencing a location's average temperature?

(1) Latitude and its influence on solar radiation received (2) Air mass influences (3) Location of high and low pressure systems (4) Heat exchange from ocean currents (5) Location of mountain barriers (6) Pattern of prevailing winds (including monsoons) (7) Distribution of land and sea (8) Altitude.

Advantages of Geostationary Orbits

(1) Make repeated observations over a given area (constant view area). (2) Get high temporal resolution data. GOES E and W can give you a temporal resolution of 1 minute!! Hence, GOES E and W can effectively monitor the severe weather environment and track severe storms and hurricanes in real time.

Advantages & disadvantages between relative humidity & dew point temperature as a moisture indicator.

(1) Relative humidity is defined as "the ration of the amount of water vapor actually in the air to the maximum amount of water vapor required for saturation at that particular temperature and pressure." There are advantages of using relative humidity to describe the air's moisture content. A hygrometer can measure relative humidity changes with nothing more than a piece of human or horse hair. It is useful to be able to express humidity as a percentage value. Gauging percentages of relative humidity, human beings on a humid summer day are able to realize that depending on the value of relative humidity, it may feel hotter than it actually is outside due to the amount of water vapor in the air. Another advantage would be the that relative humidity is the primary method of describing humidity by meteorologists, allowing for a uniformity among descriptions channel-to-channel and in day-to-day conversation. (2) Dew point temperature can be defined as "the temperature to which air must be cooled (at constant pressure and constant water vapor content for saturation to occur." An advantage of using dew point temperature is that it is a complete and unquestionable measurement of how much humidity actually exists in the air.

Tropical Cyclones

(1) Rely on warm water and latent heat of condensation for energy. (2) Warm-Core Lows: the hurricane weakens with height. (3) Centers of sinking air. (4) Winds are strongest near the surface. (5) Circular isobars with steeper pressure gradient. (6) Smaller, no fronts.

Advantages of Polar Orbiting Satellites

(1) Since the orbit is lower than for the Geostationary satellites, the data resolution is higher. (2) They provide global coverage, necessary for NWP models and climatic studies.

Stages of Development for Mid-Latitude Cycle

(1) Stationary Front (2) Front Wave (3) Open Wave (4) Mature (initial occlusion) (5) Advanced occlusion (6) Cut-off cyclone

Discuss the principal theories of precipitation.

(1) The Collision-Coalescence Process, or the warm theory, expounds that the constantly moving liquid droplets existing within a cloud (actually made of frozen liquid water or particles) crash into each other, causing the droplets to fuse together - making them bigger and weightier, allowing them a better chance to descend in the direction of Earth's surface. (2) The Ice Crystal Bergeron Process, involves ice crystals, "supercooled" liquid water (remains liquid even in below freezing environments) and "supercooled" water vapor (remains vapor even in below freezing environments) within a cloud at a temperature of less than 15 degrees Celsius. The "supercooled" water and liquid is attracted to the ice crystals. This attraction weighs down the ice crystals, growing heavier and heavier, until they become heavy enough to fall to earth as snow precipitation.

Conditions necessary for tropical cyclone formation

(1) a tropical disturbance with thunderstorms must occur (2) a distance of at least 500 kilometers (300 miles) from the equator (3) ocean temperatures of 80F or warmer to a depth of at least 50 meters below the surface (4) lots of moisture in the lower and middle part of the atmosphere (5) low wind shear.

Weather Front

A front is a transition zone between two air masses of different densities. Since density differences are most often caused by temperature differences, fronts usually separate air masses with contrasting temperatures and different humidity.

Snow

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

Sleet

A type of precipitation consisting of transparent pellets of ice 5mm or less in diameter.

Fahrenheit

Advantage: More accurate than Celsius. 0-100 degree scale demarcates the extremes of Northern climates. Disadvantage: Different degree sizes from degrees Kelvin.

Celsius

Advantage: used by most of the world

Ozone

An almost colorless gaseous form of oxygen with an odor similar to weak chlorine. The highest natural concentration is found in the stratosphere where it is known as stratospheric ozone. It also forms in polluted air near the surface where it is the main ingredient of photochemical smog.

Carbon Dioxide

Carbon dioxide can be defined as "a colorless, odorless gas whose concentration is about 0.037 percent (368 ppm) in a volume of air near sea level. It is a selective absorber of infrared radiation and, consequently, it is important in the earth's atmospheric greenhouse effect." This gas is quite important when examining the earth's weather and climate. Carbon dioxide enters Earth's atmosphere from decaying vegetation, volcanic eruption, respiratory exhalation, deforestation and burning fossil fuels. It exits the atmosphere during photosynthesis and then is stored in the roots, branches, leaves of plant life and most largely, the ocean. This greenhouse gas traps some of the outgoing energy of the earth, allowing for temperature regulation.

Convection example

Convection happens naturally in the atmosphere. On a warm, sunny day certain areas of the earth's surface absorb more heat from the sun than others; as a result, the air near the earth's surface is heated somewhat unevenly. Air molecules adjacent to these hot surfaces bunce against them, thereby gaining some extra energy by conduction. The heated air expands and becomes less dense than the surrounding cooler air. The expanded warm air is buoyed upward and rises. In this manner, large bubbles of warm air rise and transfer heat energy upward. Cooler, heavier air flows towards the surface to replace the rising air. This cooler air becomes heated in turn, rises, and the cycle is repeated.

Clouds in a Unstable Atmosphere

Cumuli-form clouds

Winter Indian Monsoon

During the winter, the air over the continent becomes much colder than the air over the ocean. A large, shallow high-pressure area develops over continental Siberia, producing a clockwise circulation of air that flows out over the Indian Ocean and South China Sea. subsiding air of the anticyclone and the downslope movement of northeasterly winds from the plateau provide eastern and Southern Asia with generally fair weather and the dry season. Hence, the winter monsoon means clear skies, with winds that blow from land to sea.

Describe the El Nino/ Southern Oscillation (ENSO) phenomenon. What are some ramifications of El Nino?

El Niño, a weather condition resulting in sizable fish populations and phosphate-laden fertilizer, tends to last for a few weeks to a month. However, when El Niño lasts for extended periods of time, the results can be catastrophic. The condition, translates to "the boy" and references the Christ child, is named for its occurrence around Christmas. Southerly winds off of the Western coastline of South America encourage the advancement of cold, nutrient-dense water, spurring fish population and in turn, carry seabird populations to prosperity. These seabirds produce phosphorus droppings, heartening the fertilizer industry. When El Niño's conditions spiral out of control, fish and marine plant life dies, resulting in seabird deaths as well. Their remains wash up on the shores of Peru, polluting both the water and beach due to the diminution of the water's oxygen. All of this occurs as a result of cool surface water in the east and warm surface water in the west along the equator and the lowering of sea level in the eastern Pacific Ocean, producing a dense coating of warm water from the West and a frail countercurrent proceeding slowly towards the western shores of South America. This also affects the southern United States. Southern Oscillation is a seesaw pattern of inverted surface air pressure at opposing ends of the Pacific Ocean. Occurring once every couple of years (and lasting between one and two years), typical surface atmospheric pressure patterns crumple to air pressure rises and falls over the respective western and eastern Pacific Ocean. Trade winds are weakened while east winds have the potential to be replaced by west winds. The west winds fortify a countercurrent, allowing for warm waters to flow east. La Niña, on the other hand, is a weather pattern diametrically opposed to El Niño. Rather than producing a "warm water" episode, La Niña produces the opposite - resulting in a cold-water episode.

Air Mass

Extremely large body of air whose properties of temperature and humidity are fairly similar in any horizontal direction at any given altitude, and may cover thousands of square kilometers.

Heat Index

Heat index is also a form of apparent temperature that combines the air temperature with relative humidity to determine how warm the air actually feels. Sweat is a form of negative control in our bodies. When we get hot we sweat, then the sweat evaporates from our skin making us feel cooler. If the humidity is high, the sweat does not evaporate and we feel even hotter. When heat index is high we feel hotter than we normally would at the actual temperature.

Stable Atmosphere

If a parcel of air is displaced (lifted) in the vertical...it will be immediately colder than the surrounding environment and will return to its original position.

Unstable Atmosphere

If a parcel of air is displaced (lifted) in the vertical...it will continue to rise until it is no longer warmer than the surrounding environment.

Summer Indian Monsoon

In summer, the wind flow pattern reverses itself as air over the continents becomes much warmer than air above the water. A shallow thermal low develops over the continental interior. The heated air within the low rises, and the surrounding air responds by flowing counterclockwise into the low center. This condition results in moisture bearing winds sweeping into the continent from the ocean. The humid air converges with a drier westerly flow, cuaising it to ris; further lifting is provided by hills and mountains. Lifting cools the air to its saturation point, resulting in heavy showers and thunderstorms. Thus, the summer monsoon of southeastern Asia, which lasts from about June through September, means wet, rainy weather (wet season) with winds that blow from sea to land.

Showers

Intermittent precipitation from a cumuliform cloud, usually of short duration but often heavy.

Importance of Standard Time Zones

It helps in the scheduling of airways and railways, satellite images, and demarcates a standard time in which a country or region can be determined.

Clouds in a Stable Atmosphere

Layered clouds

Lightning Formation

Lightning is formed during mature thunderstorms due to a discharge of electricity. Lightning can happen within a cloud, between two clouds, or between the cloud and the ground.

Rain

Precipitation in the form of liquid water drops that have diameters greater than that of drizzle.

Freezing Rain

Rain or drizzle that falls in liquid form and then freezes upon striking a cold object or ground. Both can produce a coating of ice on objects which is called glaze.

Why do seasons exist?

The four seasons happen because of the tilt of the Earth's axis. At different times of the year, the sun's rays hit different parts of the globe more directly. The angle of the Earth's axis tilts the Northern Hemisphere towards the sun during the summer. Without the tilt of the earth's axis, we wouldn't have seasons. Instead, the areas around the equator would receive the most sun and the northern and southern hemispheres would be stuck in a gradual gradient of hot to cold. The seasons would not change, it would be about the same temperature year round and there would be no seasons.

Latent Heat

The heat that is either released or absorbed by a unit mass of a substance when it undergoes a change of state, such as during evaporation, condensation or sublimation.

Hydrologic cycle

The hydrologic cycle begins with the evaporation of water from the surface of the ocean. As moist air is lifted, it cools and water vapor condenses to form clouds. Moisture is transported around the globe until it returns to the surface as precipitation. Once the water reaches the ground, one of two processes may occur; 1) some of the water may evaporate back into the atmosphere or 2) the water may penetrate the surface and become groundwater. Groundwater either seeps its way to into the oceans, rivers, and streams, or is released back into the atmosphere through transpiration. The balance of water that remains on the earth's surface is runoff, which empties into lakes, rivers and streams and is carried back to the oceans, where the cycle begins again.

Latent Heat example

The melting of ice or the boiling of water.

Shaded Area/Direct Sunlight

The temperature difference between a shaded area and an area with direct sunlight. The temperature in the shade is the actual air temperature. The temperature in direct sunlight feels warmer because the sun's radiation is directly heating our bodies.

How does the average air temperature usually change (in the troposphere) as you move higher up in elevation?

The temperature in the troposphere, stretching from Earth's surface to about 11 km into the atmosphere, commonly decreases as elevation increases. The lapse rate can be explained in layman's terms due primarily to the fact that sunlight warms the earth's surface, and the surface, in turn, warms the air above it. However, atmospheric gases and portions of the electromagnetic spectrum are involved to a great extent, and must be accounted for. Air warmed through the greenhouse effect at infrared wavelengths tends to cool as elevation increases, away from its significant heating source, the Earth. Containing 99% of the Earth's water vapor, it is obvious that this substance plays a large role in the temperature decrease with elevation. Water vapor absorbs much of the radiation and solar energy emanating from the Earth.

Conduction

The transfer of heat from molecule to molecule within a substance.

Conduction example

The transfer of heat from the hot end of the metal pin to the cool end by molecular contract.

Convection

The type of heat transfer that takes place in liquids and gases because they can move freely and it is possible to set up currents within them.

Thunder:

Thunder is formed by the heating of air which causes the air to expand. The expanding air causes a shock wave that develops into a booming sound wave which is what we call thunder. Lightning comes first because the lightning is what heats the air for thunder to occur.

Conditions favorable for a thunderstorm formation

Warm, moist air at low levels. Cool, dry air at upper levels. Upper-level divergence (above 500mb) and a synoptic scale disturbance.

Water Vapor

Water vapor is defined as "water in a vapor (gaseous) form." Depending on location, water vapour can account for a tiny portion (arctic areas) or up to 4 percent (tropical locations) of gases in the atmosphere. This gas is integral as it relates to the earth's weather and climate. Water vapor can be either a liquid or solid. It also falls to earth as precipitation. It releases sizable quantities of latent heat (while becoming liquid water or ice), providing a critical source of atmospheric energy for hurricanes and thunderstorms. Water vapor also serves as a formidable greenhouse gas. It draws in some of the outgoing radiant energy, playing a momentous role in the balance of heat and energy on the earth.

Wind Chill

Wind chill is one form of apparent temperature. Our bodies emit infrared radiation. On a cold day, this heats a small layer of air molecules around our skin that helps to keep us warm. As the wind blows, it pushes the warm layer away and makes us feel colder than the air temperature really is.