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Transcript of The Atmosphere
heat and moisture over the entire planet.
The composition of the atmosphere is important in many
ways. Some gasses are essential in maintaining life, while
others help to maintain the temperature of our planet.
Humans have even used some gasses in industries.
Weather vs. Climate
Weather is short term. Climate is long term.
All storms occur at low pressure systems with warm or moist air.
Unstable air: warm air rising in a low pressure system.
Gasses that contribute to the greenhouse effect. The greenhouse effect causes the atmosphere to trap more heat energy at the Earth's surface and within the atmosphere. Of the energy emitted back to space, 90% is intercepted and absorbed by greenhouse gasses. Without the greenhouse effect, the Earth's average temperature would be 0ºF, rather than the present 60ºF.
Together these two gases make up approximately 99% of the dry atmosphere and are very important to life. Nitrogen is an important nutrient for plant growth. Oxygen is exchanged between the atmosphere and life through photosynthesis and respiration.
Nitrogen & Oxygen
Water vapor varies in concentration in the atmosphere in both where it is and what temperature it is. The highest concentrations of water vapor are found near the equator over the oceans and tropical rain forests. Cold polar areas and subtropical continental deserts are locations where the volume of water vapor can approach zero percent.
Water vapor plays many important roles on our planet:
1. It redistributes heat energy on the Earth through changing states (solid, liquid, gas)
2. The condensation of water vapor creates precipitation that falls to the Earth's surface providing needed fresh water for plants and animals.
3. It helps warm the Earth's atmosphere through the greenhouse effect.
Carbon dioxide is one of the most famous greenhouse gasses, its concentration in the atmosphere is estimated to have increased by 35% in the last century, increasing the greenhouse effect.
Methane is a very strong greenhouse gas (200 times stronger than carbon dioxide). Since 1750, methane concentrations in the atmosphere have increased by more than 150%.
The primary sources for the additional methane added to the atmosphere (in order of importance) are:
Anaerobic conditions associated with rice paddy flooding results in the formation of methane gas. However, an accurate estimate of how much methane is being produced from rice paddies has been difficult to ascertain. More than 60% of all rice paddies are found in India and China where scientific data concerning emission rates are unavailable. Nevertheless, scientists believe that the contribution of rice paddies is large because this form of crop production has more than doubled since 1950.
Grazing animals release methane to the environment as a result of herbaceous digestion. Some researchers believe the addition of methane from this source has more than quadrupled over the last century.
Domestic Grazing Animals
Termites also release methane through similar processes. Land-use change in the tropics, due to deforestation, ranching, and farming, may be causing termite numbers to expand. If this assumption is correct, the contribution from these insects may be important.
Landfills produce methane as organic wastes decompose over time. Coal, oil, and natural gas deposits release methane to the atmosphere when these deposits are excavated or drilled.
Landfills, coal mining, and oil/gas extraction
Ozone is located in 2 areas with both beneficial and harmful effects to life.
Stratospheric ozone provides an important service to life on the Earth as it absorbs harmful ultraviolet radiation. In recent years, levels of stratospheric ozone have been decreasing due to the buildup of human created chlorofluorocarbons in the atmosphere. Since the late 1970s, scientists have noticed the development of severe holes in the ozone layer over Antarctica. Satellite measurements have indicated that the zone from 65° North to 65° South latitude has had a 3% decrease in stratospheric ozone since 1978.
Ozone is also highly concentrated at the Earth's surface in and around cities. Most of this ozone is created as a by product of human created photochemical smog. This buildup of ozone is toxic to organisms living at the Earth's surface.
The atmosphere is divided into 5 layers based on temperatures
Contains about 80% of the total mass of the atmosphere. It is also the layer where the majority of our weather occurs. Maximum air temperature also occurs near the Earth's surface in this layer. With increasing height, temperature decreases.
Contains the ozone layer. Very little weather occurs here. Occasionally, the top portions of thunderstorms breach this layer. The lower portion of the stratosphere is also influenced by the jet stream. With increasing height, temperature increases.
Contains the coldest part of the atmosphere (about -130°F). This is also the layer where falling meteors interact with air molecules, creating “shooting stars.” With increasing height, temperature decreases.
Contains the highest temperatures in the atmosphere (greater than 2200°F) from the absorption of intense solar radiation. Although these temperatures seem extreme, it would actually feel very cold because the air is extremely thin. There are too few air molecules separated by large distances to transmit this heat. With increasing height, temperature increases.
The uppermost layer where the atmosphere thins out and merges with interplanetary space. The main gasses within the exosphere are the lightest atmospheric gasses, mainly hydrogen. Since there is no clear boundary between outer space and the exosphere, it is sometimes considered a part of outer space. As with the thermosphere, with increased height, temperature increases, although there are too few molecules to transmit the heat.
uses terms like:
uses terms like:
the apparent deflection of moving objects when viewed from a rotating frame of reference. It is caused by the rotation of the Earth on its axis.
In the Northern Hemisphere, deflection occurs to the right.
In the Southern Hemisphere, deflection occurs to the left.
wind is caused by the movement of air due to changes in temperature and pressure. Hot air rises, and causes high pressure. Cold air sinks, and causes low pressure.
Global Climate Models or General Circulation Models
Computer driven models that help to explain the general circulation of the atmosphere and global climates.
assumes that the Earth is not rotating in space (no Coriolis Effect), the surface of Earth is constant (no oceans or continents), and global temperatures (cold at poles and hot at equator) create a temperature gradient.
3 Cell Model
eliminates one of the assumptions because it includes the Coriolis Effect, thus making it more complicated (having 3 convection cells)
The thermally driven circulation of air between the equator and 30° latitude that is responsible for the Trade Winds across the Atlantic Ocean.
The thermally driven circulation of air between 30° and 60° latitude that is responsible for the Westerlies (trade winds blowing from the West towards the East) across the Atlantic Ocean.
The thermally driven circulation of air between 60° latitude and the pole. It is responsible for the Polar Easterlies (weak trade winds blowing from the East towards the West) across the Atlantic Ocean.
Hot air from the equator rises.
Like a ball rolling downhill, the air moves towards the poles and cools off.
Cold air from the pole sinks.
Because the air has nowhere else to go, it moves along the surface back towards the equator where it is heated by solar energy.
the differences in air pressure throughout the atmosphere creates a textured surface with hills (high pressure areas) and valleys (low pressure areas). The air will move, much like a ball rolling downhill, from areas of high pressure to areas of low pressure. High pressure is usually associated with good weather (sunny and clear skies) while low pressure is usually associated with bad weather (storms and cloudy skies).
Simple Pressure Systems
(without the Coriolis effect: Worldwide)
Realistic Pressure Systems
(with the Coriolis effect:
In the Northern Hemisphere)
In the Northern Hemisphere, low pressure systems cause the air to move inward and counterclockwise.
High pressure systems cause the air to move outward and clockwise.
This is opposite in the Southern Hemisphere.
form when the air is unstable (the air is warm enough for it to rise) and humid.
a. Starts with a warm plume of rising air.
b. The updraft velocity increases with height.
c. Turbulent air pulls outside air into the cloud.
d. Supercooled water droplets are carried far above freezing level.
a. The heaviest rains occur.
b. The downdraft is initiated by frictional drag of the raindrops.
c. The top of the cloud approaches tropopause and forms anvil top.
a. The downdraft takes over entire cloud.
b. The storm deprives itself of moist updraft air.
c. Precipitation decreases.
d. The cloud evaporates.
form in warm, moist air in front of eastward-moving cold fronts (in the United States)
form in a similar way as thunderstorms, but they are fueled by warm water. In order for hurricanes to occur, the ocean must be warmer than 26.5°C or 81°F. Hurricanes will weaken rapidly when they travel over land and/or colder water.
i. Before thunderstorms develop, a change in wind direction and an increase in wind speed with increasing height creates an invisible, horizontal spinning effect in the lower atmosphere.
ii. Rising air within the thunderstorm updraft tilts the rotating air from horizontal to vertical.
iii. An area of rotation, 2-6 miles wide, now extends through much of the storm. Most strong and violent tornadoes form within this area of strong rotation.
when thunderstorms begin to organize their circulation and the pressure is lowered. May or may not develop into a tropical storm.
If a tropical depression grows to have wind speeds of 35-64 knots (39-73 mph), it becomes a tropical storm. The storm becomes more organized and more circular in shape - resembling a hurricane. This is when it is given a name.
If surface pressures continue to drop, the storm becomes a hurricane when wind speeds reach 64 knots (74 mph). A pronounced rotation develops around the central core.
The Trade Winds across the Atlantic Ocean affected the routes taken by explorers and merchants traveling back and forth between North America and Europe.
El Nino Explained