Introduction to Atmospheric Science Unit 1 Introduction to Atmospheric Science

1.1 Composition Our atmosphere Composition Mix of gases surrounding entire planet Held in place by gravity Filters out energy and materials from space Regulates temperature, allows for water in all 3 states Composition Nitrogen – 78% Oxygen – 21% Argon – .9% All other gases and particulants – .1%

1.1 Composition

1.1 Composition Nitrogen and oxygen Percentages are consistent to elevation of 50 miles (80 km) Balance of destruction and production Nitrogen removed mostly by soil bacteria, plankton Returned by decay of plant and animal materials Oxygen removed through chemical reaction (oxidation), organic decay, respiration Returned through photosynthesis

1.1 Composition Water vapor Invisible gas made of water molecules Substance follows the water cycle Varies greatly by location Tropical air may be up to 4% water, arctic air may barely have any Acts as a “greenhouse” gas, trapping Earth’s radiant energy Latent heat Energy stored in water molecules, gained through evaporation Released when water condenses to liquid

1.1 Composition Carbon dioxide Occupies .038%, but varies by location Enters air through decay, volcanism, exhalation of animals, burning of fossil fuels Removed through photosynthesis, dissolving into oceans, absorption by phytoplankton Oceans may hold over 50X more CO2 than air Past CO2 concentrations measured through Arctic and Antarctic ice cores Evidence shows concentrations have increased 37% since the early 1800s. Important greenhouse gas, contributes to climate change.

Stepped Art Fig. 1-4, p. 7

FIGURE 1.5 Measurements of CO2 in parts per million (ppm) at Mauna Loa Observatory, Hawaii. Higher readings occur in winter when plants die and release CO2 to the atmosphere. Lower readings occur in summer when more abundant vegetation absorbs CO2 from the atmosphere. The solid line is the average yearly value. Notice that the concentration of CO2 has increased by more than 20 percent since 1958.

1.1 Composition Ozone (O3) Most forms naturally in stratosphere Provides protection from UV rays Can be formed at surface Chemical reactions between pollutants and sunlight create ozone Called photochemical smog Irritates eyes, lungs, damages plants Common near large cities

1.1 The Early Atmosphere The Earth’s first atmosphere was composed mostly of hydrogen and helium Evolved due to outgassing of CO2, NH3, and H2O from the cooling center of the Earth Caused heavy rain that would form an early ocean Lakes and oceans acted as a sink, absorbing CO2 from atmosphere Reactions with oxygen broke down ammonia, plus volcanic eruptions produced most N2 O2 was created almost completely through photosynthesis, first by cyanobacteria Later, aquatic plants and algae, then terrestrial plants added O2 to today’s levels

1.2 Vertical Structure of the Atmosphere Air Pressure and Air Density Weight = mass x gravity Density = mass/volume Pressure = force/area At the Earth’s surface the pressure of the atmosphere is 14.7 lbs/in2 . Standard sea level pressure is 1013.25 millibars (mb) = 101,325 Pascals (Pa) = 29.92 in Hg Atmospheric pressure decreases with height.

FIGURE 1.9 Both air pressure and air density decrease with increasing altitude. The weight of all the air molecules above the earth’s surface produces an average pressure near 14.7 lbs/in.2

FIGURE 1.10 Atmospheric pressure decreases rapidly with height. Climbing to an altitude of only 5.5 km, where the pressure is 500 mb, would put you above one-half of the atmosphere’s molecules.

1.2 Vertical Structure of the Atmosphere Layers of the Atmosphere Lapse rate Change in temperature with a change in height Typically inverse relationship, decrease in temp with increase in height Isothermal environment No change in temperature with height Inversion layer Reversal of standard lapse rate Temps increase with height

1.2 Vertical Structure of the Atmosphere Layers of the Atmosphere Troposphere Decrease in temperature with height Daily weather occurs here. Extends up about 12 miles Stratosphere Ozone layer located here. Increase in temperature caused by absorption of UV by O3 12 miles up to 50 miles

1.2 Vertical Structure of the Atmosphere Mesosphere Decrease in temperature Most meteors burn up here 50 to 85 miles Thermosphere Increase in temperature Suns strongest radiation impact. Dramatic temperature swings day to night 85 miles, up to the point where no gas exists

Stepped Art Fig. 1-11, p. 13

1.2 Vertical Structure of the Atmosphere Ionosphere Not a true layer but an electrified region Created when solar energy rips electrons from gas atoms Creates ionized layers Exists at the top of the atmosphere in the thermosphere F,E,D layer Sun light creates layers, D disappears at night and less interference with AM radio transmissions.

1.3 Weather & Climate Weather Short term air temperature, air pressure, humidity, clouds, precipitation, visibility, and wind Climate Long term patterns and average weather; not just magnitude but also frequency

1.3 Weather & Climate Meteorology Study of the atmosphere and its phenomena Aristotle 340 B.C. Meterologica, meteoros: high in air 1843 telegraph 1920s air masses 1940s upper air 1950s radar and computers 1960s satellite

1.3 Weather & Climate Satellite’s View Geostationary satellite Meridians measure longitude (W-E) Parallels measure latitude (N-S) Weather maps: pressure cells, fronts, surface stations

1.3 Weather & Climate Weather and Climate in Our Lives Two general reasons for studying how weather and climate impacts our lives: economic efficiency and public safety. Clothing Crops Utilities Extreme cold and heat Tornados and hurricanes

1.3 Weather & Climate Meteorologist Any person with a college degree in meteorology or atmospheric science; not just the TV weather person Half of 9000 meteorologists employed by the US National Weather Service Researchers and operational meteorologists