23.1 Characteristics of the Atmosphere Meteorology – the study of the characteristics of the atmosphere Weather - the state of the atmosphere at a particular place and time (heat, dryness, wind, rain, sunshine, etc.) Climate - prevailing weather conditions in an area over a long period (Cold in the winter; California is getting dryer)

Composition of the Atmosphere Nitrogen – 78% Oxygen – 21% Argon– 0.9% CO 2 – 0.04% (New CO 2 data as of March 2013) Water Vapor... variable

Gas cycles Oxygen is a result of natural cycles, maintaining a chemical balance in our atmosphere. Plants release O 2 as a byproduct of photosynthesis. Plants and animals use O 2 for life processes. Nitrogen moves from the air, to soil, to living things, and back to the air. Nitrogen-fixing bacteria pull N 2 from the air and form nitrogen compounds that can be used by animals & plants. Oxygen Nitrogen

Atmospheric Pressure Gravity pulls matter toward the Earth. A 1 cm 3 column of air from sea level to the top of the atmosphere has a mass of 1.03 kg. The force of the air is 10.1N (1.03 kg x 9.80 m/s 2 = N) You can feel pressure changes in your ears when you change altitudes (mountains, airplanes)

Measuring Atmospheric Pressure Mercurial Barometer – the atmosphere presses on a liquid in a well at the base, pushing up the column of mercury. (1 atmosphere – 760 mm Hg or kPa Aneroid Barometer – Sealed container in which air has been removed. Increased pressure causes the sides to bend inward, less pressure, sides bulge out.

Layers of the Atmosphere Exosphere – up to 10,000 km (6200 mi) Merges into space; very low density Thermosphere (meaning “heat sphere”) Up to and over 640 km (400 miles) __mesopause__ Mesosphere – up to km (50-53 mi) __stratopause__ Stratosphere – up to 50 km (32 mi) __tropopause__ Troposphere- up to 7 km (23,000 ft) at the poles, and km (56,000 ft) at equator From top to bottom...

Atmosphere layer Characteristics Troposphere: very thin layer most weather occurs here warm at lower altitudes, colder at the top most dense at the surface contains 75% of the mass of the atmosphere

Atmosphere layer Characteristics Stratosphere: Tropopause to 50 km (32 mi) no water vapor; no weather contains the ozone layer temperature rises with increasing altitude From – 67 ∘ to 32 ∘ F (19 ∘ to 0 ∘ C)

Atmosphere layer Characteristics Mesosphere: Stratopause to 85 km (53 mi) Temperatures drop to -100 C Coldest layer Water vapor freezes into ice clouds Meteors burn up in this layer

Atmosphere layer Characteristics Thermosphere: Mesopause to 640 km (400 mi) Temperatures rise to 2000 C Hottest layer Solar energy absorbed, but feels very cold (few molecules) ISS orbits here Aurora borealis occurs here Ionosphere = lower portion Exosphere = outer edge