Atmosphere Notes

Earth’s Atmosphere

·        99% of gases extend only 30 km above earth’s surface

·        Weather occurs within first 10-15 km

Composition of atmosphere

·        Nitrogen 78%

·        Oxygen 21%

·        Water Vapor 0-4%

·        Carbon Dioxide .37%

·        Other gases make the rest

Atmospheric Gases

·        Nitrogen, Oxygen, Water Vapor, and cd are invisible

·        Clouds are not gas but condensed vapor in droplet form

·        Ground based smog (visible) contains reactants of nitrogen, VOC’s, and ozone

Variable and Increasing Gases

·        Nitrogen and oxygen concentration experience little change

·        Carbon Dioxide, methane, and oxides of nitrogen have increased

·        Carbon Dioxide has increased more than 18% since 1958

·        Fossil fuels are the biggest problem

Atmospheric Greenhouse Effect

·        Warming of atmosphere by absorbing and emitting of infrared radiation allowing shortwaves to pass

·        Main Gases responsible are water vapor and carbon dioxide

Aerosols and Pollutant

·        Human and natural activities displace tiny soil, salt, and ash particles as aerosols

·        Sulfur, nitrogen oxides, and hydrocarbons are released as pollutants

Pressure and Density

·        Gravity pulls gases to earth’s surface

·        At sea level these gases weigh 14.7 psi at pressure of 1013.25 mb

·        The amount of force exerted over an area is called air pressure

·        Air density is the number of air molecules in a given volume

Vertical pressure Profile

·        Atmospheric pressure decreases rapidly with height

·        Climbing to altitude of 5.5km where pressure is 500mb would put you above ½ of the atmosphere’s molecules

Lapse Rate

·        Rate in which air temperature decreases with height

·        Average lapse rate in the lower atmosphere is about 6.5 degrees C per 1 km or 3.6 degrees F per 1000 ft.

Atmospheric Layers

·        Layers are defined by constant trends in average air temperature (changes with pressure and radiation)

·        Troposphere 2.Stratosphere 3.Mesosphere 4.Thermosphere 4. Exosphere

Solar Radiation

·        Albedo: fraction of solar radiation reflected back to space

·        Absorption: fraction of solar radiation not reflected into space

Urban Heat Island Effect

Metropolitan area warmer than surrounding rural areas

UHI effect is caused primarily by modification of land surfaces in developments that use materials that retain heat

Cloud Triangle

·        Based on altitude

·        0-2000m Stratus, cumulus

·        2000-6000m altostratus, altocumulus

·        6000+ m Cirrostratus, cirrocumulus, cirrus

Low Clouds with Precipitation

·        Nimbostratus, Cumulonimbus

Air Pressure

·        Warm air = expanding or rising air = low air pressure

·        Cold air = sinking air = high air pressure

Wind Movement

·        Uneven heating of Earth’s surface causes some areas to be warmer than others

·        Warm follows cold to share warmth, when this happens in the atmosphere we get wind

Pressure Wind and weather

·        Winds: horizontal flow of air from high pressure to low

·        Pressure: tendency of air rising or sinking at any given time

Humidity

Measure of amount of water vapor stuck between molecules in the air

Airs ability to hold water depends on air temperature

Relative Humidity

Amount of water vapor (%) compared to the amount that air can hold

100% is saturated air