What is the Climate of the Earth’s Atmosphere?

What is the Climate of the Earth’s Atmosphere? CLIM 101

Earth’s Atmosphere The Earth is enveloped in a layer of gases, which we call the atmosphere. Life on Earth is supported by the atmosphere. The atmosphere absorbs energy from the Sun, recycles water and other chemicals, and provides a moderate climate. The atmosphere also protects life near the surface of Earth from high- energy radiation coming from the Sun and outer space. The envelope of gas surrounding the Earth changes from the ground up. Four layers can be distinguished by their temperature, chemical composition, and density. greenhouse gases in bold

Questions What is the origin of Earth’s atmosphere? Why is the sky blue? What is a thunderstorm? Tornado? Hurricane? Monsoon? Why is it colder in winter than summer? Why isn’t the temperature in Fairfax the same every 4 September?

Origin of Earth’s Atmosphere ~5 billion years ago - first Earth atmosphere • Original atmosphere primarily He2 and H2 • Dissipated by heat from the still-molten crust and the Sun • Possibly blown away by strong solar wind

Origin of Earth’s Atmosphere ~ 4.4 billion years ago - second Earth atmosphere • After Earth’s crust formed, many volcanoes released steam (H2O), CO2, and NH3 (virtually no O2) • 100 times as much gas as the current atmosphere, but as it cooled much of the CO2 was dissolved in the seas and precipitated out as carbonates • The later "second atmosphere" contained largely N2 and CO2 • Greenhouse effect, caused by high levels of CO2 and CH3, kept the Earth from freezing

Origin of Earth’s Atmosphere ~ 3.3 billion years ago - third Earth atmosphere • Early bacteria (cyanobacteria) produced O2 while sequestering CO2 in organic molecules • Later, photosynthesizing plants evolved and continued releasing O2 and sequestering CO2. Over time, excess carbon became locked in fossil fuels, sedimentary rocks (e.g. limestone), and animal shells. • As O2 was released, it reacted with NH3 to release N2; in addition, bacteria would also convert NH3 into N2. • Currently, most N2 results from photolysis of volcanic NH3 • As more plants appeared, the levels of O2 increased significantly, while CO2 levels dropped. With the appearance of an ozone (O3) layer, life forms were better protected from ultraviolet radiation. • Current atmospheric composition enforced by oceanic blue-green algae & geological processes • O2 consumed by inorganic chemical reactions, animals, bacteria, and land plants • CO2 produced by respiration and decomposition and oxidation of organic matter • O2 would vanish within a few million years by chemical reactions, and CO2 dissolves easily in water and would be gone in millennia if not replaced

Questions What is the origin of Earth’s atmosphere? Why is the sky blue? What is a thunderstorm? Tornado? Hurricane? Monsoon? Why is it colder in winter than summer? Why isn’t the temperature in Fairfax the same every 9 September?

Summer 2003 European Heat Wave: Result of Global Warming? The proximate cause of the heat-wave was a persistent high pressure center over Northwest Europe. What made the high persist? Summer 2003 temperatures relative to 2000-2004

Lake Delton, WI Rail line in Iowa Midwest Floods: May-June 2008 Downtown Cedar Rapids, IA The proximate cause of the 2008 Midwest floods was unusually intense, frequent rains in Iowa in May-June. What made the rain so unusual?

The Climate of a Planet Depends On … Energy from the Sun (+ energy from the interior) Planetary Albedo Speed of Planet’s Rotation Mass of the Planet Radius of the Planet Atmospheric Composition Ocean-Land, Topography S   M r H2O, CO2, O3, clouds h*

S, , a, g, Ω O3 H2O CO2 Ω CLIMATE DYNAMICS OF THE PLANET EARTH g  (albedo) Gases: H2O, CO2, O3 S r T4 h*: mountains, oceans (SST) w*: forest, desert (soil wetness) CLIMATE . stationary waves (Q, h*), monsoons WEATHER hydrodynamic instabilities of shear flows; stratification & rotation; moist thermodynamics day-to-day weather fluctuations; wavelike motions: wavelength, period, amplitude

Climate of the Atmosphere • Energy balance • Greenhouse effect • Energy imbalance  heat transport • mass flux (Hadley cell) • latent heat transport (phase change of water) - hydrologic cycle • Observed distribution of temperature, pressure, humidity, wind, precipitation with latitude, vertical • Causes of variability (decreasing scale) • Land-sea contrast • Large-scale: monsoons • Small-scale: sea breeze • Stationary waves • Transient (baroclinic) waves • Tropical cyclones • Convection (thunderstorms, tornadoes)

Terrestrial energy emission Solar energy flux Planetary albedo Earth’s Energy Balance Solar Radiation S = 1380 Wm-2 (plane, parallel) Planetary Emission, E In equilibrium, INCOMING ENERGY = OUTGOING ENERGY (1 - ) S  r2 = E (4  r2) [r = 6373 km]

Earth’s Energy Balance Solar Radiation S = 1380 Wm-2 (plane, parallel) Planetary Emission In equilibrium, INCOMING ENERGY = OUTGOING ENERGY (1 - ) S  r2 = E (4  r2) E = 1/4 (1 - ) S Measured albedo () = 0.31 Calculated planetary E = 238 Wm-2 Measured planetary E = 237 Wm-2 Implied TE = 255°K (-18°C; 0°F) (because E = T4 where  = 5.67 x 10-8 Wm-2 K-4) This is a VSCM: Very Simple Climate Model

Earth’s Energy Balance Solar Radiation S = 1380 Wm-2 (plane, parallel) Planetary Emission In equilibrium, INCOMING ENERGY = OUTGOING ENERGY (1 - ) S  r2 = E (4  r2) E = 1/4 (1 - ) S Measured albedo () = 0.31 Measured planetary E = 237 Wm-2 Implied TE = 255 K (-18°C; 0°F) Measured surface Es = 390 Wm-2 Measured Ts = 288°K (+ 15°C; 40°F) WHAT’S GOING ON?

Hence the term, “Greenhouse Effect”

Electromagnetic Spectrum 255 K

CH4 methane nitrous oxide N2O oxygen ozone O2 & O3 carbon dioxide CO2 water vapor H2O

CLIMATE DYNAMICS OF THE PLANET EARTH: Energy Balance

Mean Meridional Streamfunction

The Climate of a Planet Depends On … Energy from the Sun (+ energy from the interior) Planetary Albedo Speed of Planet’s Rotation Mass of the Planet Radius of the Planet Atmospheric Composition Ocean-Land, Topography S   M a H2O, CO2, O3, clouds h*

Three Phases of Water Water can exist in all three phases in the atmosphere Even though water makes up only a small percentage of the total matter in the atmosphere, it is still one of the most important atmospheric substances. The main reason for this is that water can exist in all three phases at common temperatures found in the atmosphere. Water is the only known substance that commonly exists in all three phases at once. The speed of the individual water molecules determines what phase each molecule exists in. The slowest moving molecules exist as ice. The water molecules in ice are locked into a hexagonal crystal and do not move freely. Liquid water molecules are moving fast enough to break free from the crystal structure, but they are still attached to each other. Liquid water can assume the shape of its container. The water molecules in the vapor phase are moving fast enough so that they bounce off of each other and do not become attached. Science and Technology, Thompson

Latent heat: How it warms or cools air Latent heat is the energy given up or taken up by the air or other substances as water changes phase, such as vapor condensing into liquid. During evaporation, the phase changes from liquid to vapor. The molecules of liquid water can absorb energy (in the form of radiation or from the warm air molecules around them). When enough energy is absorbed, the water molecules move fast enough to become vapor. As water molecules absorb energy from neighboring air molecules, the air molecules slow down. This lowers their temperatures; the air cools. Perspiration evaporating from our bodies cools us by taking heat energy from our skin in a similar way. Heat is added to the air when water condenses from vapor into the liquid phase. The result is that the warm air becomes more buoyant than neighboring air molecules and rises. Water that is transported in the vapor phase from one place to another effectively transports heat. The heat absorbed during evaporation can be released at a different place when the phase changes back to liquid. Science and Technology, Thompson

Water Reservoirs

Climate of the Atmosphere • Energy balance • Greenhouse effect • Energy imbalance  heat transport • mass flux (Hadley cell) • latent heat transport (phase change of water) - hydrologic cycle • Observed distribution of temperature, pressure, humidity, wind, precipitation • Causes of variability (decreasing scale) • Land-sea contrast • Large-scale: monsoons • Small-scale: sea breeze • Stationary waves • Transient (baroclinic) waves • Tropical cyclones • Convection (thunderstorms, tornadoes)

July January

Zonal mean temperature January mean, zonal mean temperature

January mean, zonal mean zonal wind

Zonal Mean Zonal Wind in Dec-Jan-Feb

July January

Precipitation Jan-Feb-Mar Jun-Jul-Aug

What is the Climate of the Earth’s Atmosphere?