Geosystems Unit 7/8

atmosphere warming

49% absorbed by earth surfaces 20% reflected back by clouds 20% absorbed by atmospheric and clouds 6% scattered b atmosphere 5% reflected by earth's surface

Composition of the Atmosphere

78% nitrogen, 21% oxygen, 1% other

Stationary Front

A boundary between two different air masses, neither of which is strong enough to replace the other. Light rain over several days

Cold Front

A cold mass moving in to replace warmer air. Moves about twice as fast as warm front. Denser so it moves under the warmer air, pushing it up (vertical flow). Results in decreased humidity, change in wind direction, short period of precipitation, and summer thunder storms

weather front

A front is a boundary that separates opposing air masses. Fronts are common in the mid latitudes where polar and tropical air meet. This interaction between air masses results in movement based on density. (temperature and humidity)

Ice Ages

A good example of climatic change involves glaciers, which have alternately advanced and retreated over the past 2 million years. At times, much of Earth's surface was covered by vast sheets of ice. During these periods of extensive glacial coverage, called ice ages, average global temperatures decreased by an estimated 5°C. Global climates became generally colder and snowfall increased, which sparked the advance of existing ice sheets. Ice ages alternate with warm periods—called interglacial intervals—and Earth is currently experiencing such an interval. The most recent ice age ended only about 10,000 years ago. In North America, glaciers spread from the east coast to the west coast and as far south as Indiana.

Air Mass

A large body of air in the lower troposphere has uniform characteristics: Similar Temperature, humidity, and pressure. The interaction of air masses is what causes local weather.

Isobars

A line connecting points of equal atmospheric pressure. Measured in millibars- mb. One millibar is equal to about .2953 inches of mercury. An area where air pressure changes quickly. Barometric pressure

Formation of Tornado

A tornado forms when wind speed and direction change suddenly with height, a phenomenon associated with wind shear. Tornadoes form when small pockets of cooler air are given a horizontal, rolling-pin type of rotation near Earth's surface. If this rotation occurs close enough to the thunderstorm's updrafts, the twisting column of wind can be tilted from a horizontal to a vertical position. As updrafts stretch the column the rotation is accelerated. Air is removed from the center of the column, which in turn lowers the air pressure in the center. The extreme pressure difference between the center and the outer portion of the tornado produces the violent winds associated with tornadoes. Although tornadoes rarely exceed 200 m in diameter and usually last only a few minutes, they can be extremely destructive. A tornado is classified according to its destructive force.

Warm Front

A warm air mass is replacing a cold air mass. Air behind the front is warm and moist. Pressure goes down. Slow moving, gradual rise of warm air over cold air. Widespread, continuous precipitation occurs along and ahead of the front. Less dense so rises up over cold air. Moves about half as fast as a cold front.

Effects of Global Warming

Agriculture will be negatively affected. Drought will reduce crop yield. Reduction in water resources will make irrigation difficult. Location of farms will need to move farther from the equator. Crop types may no longer be viable. Tourism Summer seasons may be extended. Coastal resorts may need to move to the North to continue getting sun, sea, and sand. Winter sports vacations (skiing/snowboarding) may not happen anymore due to lack of snow and ice. Reduced precipitation may make some resorts uneconomic due to lack of water resources. Reduction in biodiversity Loss in ecosystem services (primary productivity, pollination, flood control) Ocean acidification Malaria is likely to spread. Coastal flooding in the Netherlands, Egypt and Bangladesh displacing 200 million people. An increase in storm activity Reduced rainfall over the USA and southern Europe. A 35% drop in crop yields in Africa and the Middle East if temperatures go up by 3C. About 200 million more people would be exposed to hunger if temperatures go up by 2C, 500 million if by 3C. About 40% of species of wildlife is expected to become extinct if we increase by 2C.

Exosphere

Air is very thing GPS satellites orbit the earth here

Mesosphere

Air temperature decreases with height above Earth. Coldest layer. Protects earth- meteoroids usually burn up in this layer

Stratosphere

Air temperature increases with height above earth due to ozone absorption of sunlight. Very calm layer allows for undisturbed flight. Ozone layer is found near the bottom of this layer

Flooding

An individual thunderstorm can unleash enough rain to produce floods, and hurricanes also cause torrential downpours, which result in extensive flooding. Floods can also occur, however, when weather patterns cause even mild storms to persist over the same area. For example, a storm with a rainfall rate of 1.5 cm/h is not much of a problem if it lasts only an hour or two. If this same storm were to remain over one area for 18 hours, however, the total rainfall would be 27 cm, which is enough to create flooding in most areas. Low-lying areas are most susceptible to flooding, making coastlines particularly vulnerable to storm surges during hurricanes. Rivers in narrow-walled valleys and streambeds can rise rapidly, creating high-powered and destructive walls of water. Building in the floodplain of a river or stream can be inconvenient and potentially dangerous during a flood. Flash-flooding can occur when rainfall happens in areas that typically receive very little rainfall.

Heat Waves

An unpleasant side effect of droughts often comes in the form of heat waves, which are extended periods of above-average temperatures. Heat waves can be formed by the same high-pressure systems that cause droughts. As the air under a large high-pressure system sinks, it warms by compression and causes above-average temperatures. The high-pressure system also blocks cooler air masses from moving into the area, so there is little relief from the heat.

Wind creation

As temperature and pressure cause the air in the atmosphere to move around, the moving air creates what we know of as wind.

Thunderstorm Life Cycle

Cumulus stage In the cumulus stage, air starts to rise vertically, as shown in Figure 13.4. The updrafts are relatively localized and cover an area of about 5-8 km. This creates updrafts, which transport water vapor to the cooler, upper regions of the cloud. The water vapor condenses into visible cloud droplets and releases latent heat. As the cloud droplets coalesce, they become larger and heavier until the updrafts can no longer sustain them and they fall to Earth as precipitation. This begins the mature stage of a thunderstorm. Mature stage In the mature stage, updrafts and downdrafts exist side by side in the cumulonimbus cloud. Precipitation, composed of water droplets that formed at high, cool levels of the atmosphere, cools the air as it falls. The newly cooled air is more dense than the surrounding air, so it sinks rapidly to the ground along with the precipitation. This creates downdrafts. The updrafts and downdrafts form a convection cell which produces the surface winds associated with thunderstorms. The average area covered by a thunderstorm in its mature stage is 8-15 km. Dissipation stage The convection cell can exist only if there is a steady supply of warm, moist air at Earth's surface. Once that supply is depleted, the updrafts slow down and eventually stop. In a thunderstorm, the cool downdrafts spread in all directions when they reach Earth's surface. This cools the areas from which the storm draws its energy, the updrafts cease, and clouds can no longer form. The storm is then in the dissipation stage. This stage will last until all of the previously formed raindrops have fallen.

deforestation

Deforestation—the mass removal of trees—also plays a role in increasing levels of atmospheric carbon dioxide. During photosynthesis, vegetation removes carbon dioxide from the atmosphere. When trees are cut down photosynthesis is reduced, and more carbon dioxide remains in the atmosphere. Many scientists suggest that deforestation intensifies global warming trends.

Moisture for Thunderstorms. Step #1

First, for a thunderstorm to form, there must be an abundant source of moisture in the lower levels of the atmosphere. Air masses that form over tropical oceans or large lakes become more humid from water evaporating from the surface below This humid air is less dense than the surrounding dry air and is lifted. The water vapor it contains condenses into the droplets that constitute clouds. Heat released from the water vapor during the process of condensation warms the air causing it to rise further, cool further, and condense more of its water vapor.

Air Pressure Types

High Pressure: As air cools, it becomes more dense and sinks toward the Earth's surface spinning clockwise. Sunny, clear skies, calm winds, spiral clockwise, cool, dry air. Low Pressure: As air warms, it becomes more dense and rises above the Earth's surface spinning counterclockwise. Cloudy, stormy skies, strong winds. spiral counterclockwise, warm moist air

Greenhouse Gases and Human Activities

Human activities increase levels of greenhouse gases (CO2, CH4, H2O) in the atmosphere, which leads to: An increase in the average global temperature Increased frequency and intensity of extreme weather events (like hurricanes) The potential for long-term change in climate and weather patterns Rise in sea level.

High Pressure Systems

In a surface high-pressure system, sinking air moves away from the system's center when it reaches Earth's surface. The Coriolis effect causes the sinking air to move to the right, making the air circulate in a clockwise direction in the northern hemisphere and in a counter-clockwise direction in the southern hemisphere. High-pressure systems are usually associated with fair weather. They dominate most of Earth's subtropical oceans and provide generally pleasant weather.

Low Pressure Systems

In surface low-pressure systems, air rises. When air from outside the system replaces the rising air, this air spirals inward toward the center and then upward. Air in a low-pressure system in the northern hemisphere moves in a counterclockwise direction. The opposite occurs in the southern hemisphere for a low-pressure system. As air rises, it cools and often condenses into clouds and precipitation. Therefore, a low-pressure system, whether in the northern or southern hemisphere, is often associated with cloudy weather and precipitation.

Lightning

Lightning is the transfer of electricity generated by the rapid rushes of air in a cumulonimbus cloud. Clouds become charged when friction between the updrafts and downdrafts within a cumulonimbus cloud removes electrons from some of the atoms in the cloud. The atoms that lose electrons become positively charged. Other atoms receive the extra electrons and become negatively charged. This creates regions of air with opposite charges. Eventually, the differences in charges break down, and a channel of partially charged air is formed between the positive and negative areas. The channel of partially charged air is called a stepped leader, and it generally moves from the center of the cloud toward the ground. When the stepped leader nears the ground, a branched channel of positively charged particles, called the return stroke, rushes upward to meet it. The return stroke surges from the ground to the cloud, illuminating the connecting channel with about 100 million volts of electricity. That illumination is the brightest part of lightning.

Troposphere

Lowest layer, most atmospheric air is found here. Air temperature decreases with height above Earth. Virtually all weather occurs here.

Burning Fossil Fuels

One of the main sources of atmospheric carbon dioxide from humans is from the burning of fossil fuels including coal, oil, and natural gas. Ninety-eight percent of these carbon dioxide emissions in the United States come from burning fossil fuels to run automobiles, heat homes and businesses, and power factories. Almost any process that involves the burning of fossil fuels results in the release of carbon dioxide. Burning fossil fuels also releases other greenhouse gases, such as methane and nitrous oxide, into the atmosphere.

Ionosphere

Particles become electrically charged. Radiowaves are bounced off the ions and reflect back to Earth

relationship between kinetic energy and temperature.

Particles have more kinetic energy when they are moving faster, so the higher the temperature of a material, the faster the particles are moving.

Strong Winds

Rain-cooled downdrafts descend to Earth's surface during a thunderstorm and spread out as they reach the ground. Sometimes, instead of dispersing that downward energy over a large area underneath the storm, the energy becomes concentrated in a local area. The resulting winds are exceptionally strong, with speeds of more than 160 km/h. Violent downdrafts that are concentrated in a local area are called downbursts. Based on the size of the area they affect, downbursts are classified as either macrobursts or microbursts. Macrobursts can cause a path of destruction up to 5 km wide. They have wind speeds of more than 200 km/h and can last up to 30 minutes. Smaller in size, though deadlier in force, microbursts affect areas of less than 3 km but can have winds exceeding 250 km/h. Despite lasting fewer than 10 minutes on average, a microburst is especially deadly because its small size makes it extremely difficult to predict and detect.

Lifting for Thunderstorm. STEP #2

Second, there must be a way for condensing moisture to release its latent heat. This occurs when a warm air mass is lifted into a cooler region of the atmosphere. Dense, cold air along a cold front can push warmer air upward, just like an air mass does when moving up a mountainside. Warm land areas, heat islands such as cities, and bodies of water can also provide heat for lifting an air mass. Only when the water vapor condenses can it release latent heat and keep the cloud rising.

Supercells

Severe thunderstorms can develop into self-sustaining, extremely powerful storms called supercells. Supercells are characterized by intense, rotating updrafts taking 10 to 20 minutes to reach the top of the cloud. These furious storms can last for several hours and can have updrafts as strong as 240 km/h. A supercell can spawn long-lived tornadoes. The picture shows an illustration of a supercell. Notice the anvil-shaped cumulonimbus clouds associated with severe storms. The tops of the supercells are chopped off by wind shear. Of the estimated 100,000 thunderstorms that occur each year in the United States, only about 10 percent are considered to be severe, and fewer still reach classic supercell proportions.

Long Term Climate Change

Some years might be warmer, cooler, wetter, or drier than others, but during the average human lifetime, climates do not appear to change significantly. Earth's history over hundreds of thousands of years shows that climates have always been, and currently are, in a constant state of change. These changes usually take place over long time periods.

Water Storage: Atmosphere

Superhighway used to transport water around the globe. Involves condensation and precipitation.

Enhanced Global Warming

Temperatures worldwide have shown an upward trend since the Industrial Revolution with several of the warmest years on record having occurred within the last two decades. If the trend continues, polar ice caps and mountain glaciers might melt. This could lead to a rise in sea level and the flooding of coastal cities. Other possible consequences include the spread of deserts into fertile regions, an increase in sea surface temperature, and an increase in the frequency and severity of storms. Based on available temperature data, many scientists agree that global warming is occurring. They disagree, however, about what is causing this warming. Some scientists hypothesize that natural cycles adequately explain the increased temperatures. Mounting evidence suggests that the rate of global temperature changes over the past 150 years are largely due to human activity.

The Coriolis Effect

The effect of Earth's rotation on the direction of winds and currents.

Formation of a Hurricane

The first indications of a building tropical cyclone is a moving tropical disturbance. Less-dense, moist air is lifted, triggering rainfall and air circulation. As these disturbances produce more precipitation, more latent heat is released. In addition, the rising air creates an area of low pressure at the ocean surface. As more warm, dense air moves toward the low-pressure center to replace the air that has risen, the Coriolis effect causes the moving air to turn counterclockwise in the northern hemisphere. This produces the cyclonic (counterclockwise) rotation of a tropical cyclone. When a disturbance over a tropical ocean acquires a cyclonic circulation around a center of low pressure, it has reached the developmental stage and is known as a tropical depression.

How thunderstorms form

The stability of the air is determined by whether or not an air mass can lift. Cooling air masses are stable and those that receive warming from the land or water below them are not. Under the right conditions, convection can cause a cumulus cloud to grow into a cumulonimbus cloud. The conditions that produce cumulonimbus clouds are the same conditions that produce thunderstorms. For a thunderstorm to form, three conditions must exist: a source of moisture, lifting of the air mass, and an unstable atmosphere.

Air stability. STEP #3

Third, if the surrounding air remains cooler than the rising air mass, the unstable conditions can produce clouds that grow upward. This releases more latent heat and allows continued lifting. However, when the density of the rising air mass and the surrounding air are nearly the same, the cloud stops growing.

Greenhouse Effect

This process of the absorption and radiation of energy in the atmosphere results in the greenhouse effect—the natural heating of Earth's surface caused by certain atmospheric gases called greenhouse gases. The greenhouse effect warms Earth's surface by more than 30°C. Without the greenhouse effect, life as it currently exists on Earth would not be possible LINK to animation Scientists hypothesize that it is possible to increase or decrease the greenhouse effect by changing the amount of atmospheric greenhouse gases, particularly carbon dioxide and methane. An increase in the amount of these gases would theoretically result in increased absorption of energy in the atmosphere. Levels of atmospheric carbon dioxide and methane are increasing. This can lead to a rise in global temperatures, known as global warming.

Droughts

Too much dry weather can cause nearly as much damage as too much rainfall. Droughts are extended periods of well-below-average rainfall. Droughts are usually the result of shifts in global wind patterns that allow large, high-pressure systems to persist for weeks or months over continental areas. Under a dome of high pressure, air sinks on a large scale. Because the sinking air blocks moisture from rising through it, condensation cannot occur, and drought sets in until global patterns shift enough to move the high-pressure system.

occluded front

Two cold air masses converge on a warm air mass. Occurs when a fast moving cold front overtakes a warm front pushing it up and cold air. Thundershowers form along the front. After frontal passage the sky is usually clear and dry

El Niño

Under normal conditions in the southeastern Pacific Ocean, atmospheric and ocean currents along the coast of South America move north, transporting cold water from the Antarctic region. Meanwhile, the trade winds and ocean currents move westward across the tropics, keeping warm water in the western Pacific. This circulation, driven by a semi-permanent high-pressure system, creates a cool, dry climate along much of the northwestern coast of South America. Occasionally, however, for reasons that are not fully understood, this high-pressure system and its associated trade winds weaken drastically, which allows the warm water from the western Pacific to surge eastward toward the South American coast. These conditions are referred to as an El Niño event. The sudden presence of this warm water heats the air near the surface of the water. Convection currents strengthen, and the normally cool and dry northwestern coast of South America becomes much warmer and wetter. The increased convection pumps large amounts of heat and moisture into the upper atmosphere, where upper-level winds transport the hot, moist air eastward across the tropics. This hot, moist air in the upper atmosphere is responsible for dramatic climate changes, including violent storms in California and the Gulf Coast, stormy weather to areas farther east that are normally dry, and drought conditions to areas that are normally wet. Eventually, the South Pacific high-pressure system becomes reestablished and El Niño weakens. Sometimes the trade winds blow stronger than normal and warm water is pulled across the Pacific toward Australia. The coast of South America becomes unusually cold and chilly. These conditions are called La Niña.

Temperature and density relationship

Warm Air - as temperature increases, density decreases Warm Air - is less dense and will RISE - it moves up because the warmer air molecules are more spread out (they are moving faster and have expanded) more than the surrounding air. We describe warmer air as having less pressure.

Temperature and Humidity

Warmer temperatures can evaporate more water from liquid to gas (water vapor). This increases the humidity. When temperature are colder there is less evaporation into the air and less humidity.

Short Term Climate Change

While an ice age might last for several million years, other climatic changes occur over much shorter time periods. The most obvious of these are seasons, which are short-term periods of climatic change caused by regular variations in daylight, temperature, and weather patterns.

Tornado distribution

While tornadoes can occur at any time and at any place, there are some times and locations where they are more likely to form. Most tornadoes — especially violent ones — form in the spring during the late afternoon and evening, when the temperature contrasts between polar air and tropical air are the greatest. Large temperature contrasts occur most frequently in the central United States, where cold continental polar air collides with maritime tropical air moving northward from the Gulf of Mexico. These large temperature contrasts often spark the development of supercells, which are each capable of producing several strong tornadoes. More than 700 tornadoes touch down each year in the United States. Many of these occur in a region called "Tornado Alley," which extends from northern Texas through Oklahoma, Kansas, and Missouri.

Weather Fronts

Zones in which air masses interact.

Air masses

air masses can originate over land (continental) and over water (maritime). Cold air masses tend to approach from the North, NW, and West. Warm air masses tend to come from the South, SE, and East

What gives wind its mass?

air molecules

Atmospheric Density

at greater altitude the same volume contains fewer molecules of gasses. lower altitude is more pressure

Layer Boundaries

differences in temperatures separate each layer from next. Temperature remains constant through boundary. Boundaries: Tropopause, Stratopause, Mesopause

Thermosphere

heat sphere. Space shuttle orbits here. Ionosphere- lower portion Exosphere- upper part Aurora Borealis(Northern Light)

Local Patterns

hey are classified based on where they originate (either over land or water) and this will determine the humidity.

Air moves from ..... this movement is experienced as ....

high to low pressure this movement is experienced as wind

atmosphere

layer of gasses that surround the earth. Its purpose is to support life on earth by protecting if from dangerous electromagnetic radiation. Create and control weather and climate. Provide gases plants and animals need to breathe

Weather in the Troposphere: Moisture (water vapor)

moisture moves through the water cycle; surface water is heated by the sun to start evaporating, then it condenses and precipitates. Humidity- depends on amount of water vapor in the air and air temperature

Denser air=?

more air pressure. That means it will press harder on things, and air around it.

gases important to life on earth

nitrogen, oxygen, water vapor, carbon dioxide

how do we measure kinetic energy of the particles in a materials.

temperature.

Humidity

the amount of water vapor in the atmosphere at a given location on Earth's surface.

atmospheric pressure

the pressure exerted on earth by the atmosphere. decreases with increased altitude. 14.7 pounds per square inch at sea level.

Air pressure

the pressure exerted on something by the weight of the atmosphere above it. The pressing force of the air molecules on each other, and on the surface of the earth

Layers of the atmosphere

troposphere, stratosphere, mesosphere, thermosphere, exosphere. Tropopause, Stratopause, Mesopause

Precipitation

water released from clouds in the form of rain, freezing rain, sleet, snow, or hail. Provides the delivery system of atmospheric water to the Earth