SOAR 2005: SOAR 2005 Energy and Circulation in the Atmosphere


Earth: Earth Complex atmospheric evolution Primordial Atmosphere Lost to space H & He very light molecules, escape easily Initially like Venus & Mars: mostly CO2 THEN Water condensed into oceans Oceans absorbed CO2 Locked it into rocks (CaCO3 = limestone) Life flourished in oceans Released free oxygen Sedimentary rocks turned red Ozone layer formed


Evolution of Earth’s Atmosphere: Evolution of Earth’s Atmosphere Oxygen content created, maintained by life.


Atmospheric Structure: Atmospheric Structure Layers (from surface) due to Density (Pressure) Radiation Environment Temperature


Atmospheric Structure: Atmospheric Structure Layers By Function Ozonosphere (O3 layer) Upper portion of Stratosphere Absorbs UV (0.1-0.3 nm), radiates IR Warmest layer in atmosphere Harmed by CFC’s Cl + 2O3  Cl + 3O2 … and Cl is free to kill again! Ozone constantly created & destroyed by UV, CFC’s increase destruction Hole in the ozone layer over Antarctica


Air Pressure: Air Pressure Pressure is force/area = weight of air column 1 in2 column weight = 14.7 lb 1 m2 column weight = 10 tonnes 1 tonne = 1000 kg = 2204 lb Why doesn’t the air pressure crush you when you lie down?


Air Pressure: Air Pressure Standard Atmosphere 760 mm Hg 29.92 in Hg 33.9 ft. H2O 1013 millibars (mb) 1013 hPa hectopascals Weight of column of Hg Weight of Hg = Weight of Air Weight of column of air Hg(tube area)(column height) = (air presure)(bowl area)


Driving Forces: Driving Forces Gravitational Force Earth’s gravity holds atmosphere Pressure Gradient force isobar = line of constant pressure Pressure Gradient force acts perpendicular


Driving forces: Driving forces Pressure Gradient force from high pressure to low pressure


Driving Forces: Driving Forces Coriolis Force Acts ONLY ON MOVING objects proportional to velocity ( ) perpendicular to velocity acts over large distances Does not determine direction water spins down a drain! The rolling ball follows a straight path seen from above, a curved path seen from the rotating reference frame (riding on the merry-go-round).


Coriolis Force: Coriolis Force Different latitudes “orbit” axis at different speeds.


Coriolis Force: Coriolis Force All moving objects are deflected to their right in northern hemisphere to their left in southern hemisphere Coriolis force deflects velocity no matter what the original direction of the velocity!


Coriolis Force:: Coriolis Force: All moving objects are deflected to their right in northern hemisphere to their left in southern hemisphere


Coriolis Force: Coriolis Force Northern Hemisphere Moving objects deflected to their own right. Southern Hemisphere Moving objects deflected to their own left. Storms rotate counterclockwise Storms rotate clockwise


Cyclones & Anticyclones: Cyclones & Anticyclones Cyclone – circulation around low pressure CCW in northern hemisphere CW in southern hemispere Anticyclone – circ. around high pressure CW in northern hemisphere CCW in southern hemisphere http://www.usatoday.com/weather/tg/whighlow/whighlow.htm


Energy Budget: Energy Budget Insolation Sun’s incident energy drives air motions (energy from deep interior adds a tiny bit) Distribution of Sunlight Reflection from clouds, landscape Absorption by atmosphere Absorption by surface Albedo = ratio of sunlight reflected Earth: 0.367 Moon: 0.113 Mars: 0.15 Venus: 0.84


Insolation: 1,373 W/m2: Insolation: 1,373 W/m2 30% Reflected by atmosphere 20% Absorbed by atmosphere 50% Absorbed by Earth’s surface Most solar energy comes in as light (shortwave radiation)


Greenhouse Effect: Greenhouse Effect Light from sun gets absorbed by Earth Earth radiates infrared


Greenhouse Effect: Greenhouse Effect Light from sun gets absorbed by Earth Earth radiates infrared Earth re-emits energy absorbed from sunlight as infrared infrared


Greenhouse Effect: Greenhouse Effect IR gets absorbed by atmosphere  Air heats  Air absorbs more water  Moist air absorbs more IR & heats more  absorbs more water


Energy Flow from Surface: Energy Flow from Surface 7% conducted to air 20% radiated as IR (longwave) % of total insolation 23% transferred by water


Energy Transfer: Energy Transfer Convection – hot stuff moves Conduction – hot stuff heats neighbors Radiation – heat moves as IR radiation


Energy Transfer by Water: Energy Transfer by Water Specific Heat Energy absorbed/released to change temp. Latent Heat Energy needed to change phase (substance remains at same temperature)


Energy Transfer by Water: Energy Transfer by Water Specific Heat Energy absorbed or released to change temp. Raising 1 kg of water 1°C absorbs 4,168 Joules 10 cm square cube of water 1 kg 4000 Joules ≈ energy to lift 400 kg or 900 lb 1 m


Energy Transfer by Water: Energy Transfer by Water Latent Heat Energy absorbed or released to change phase Evaporating 1 kg of water absorbs 2,257,000Joules 10 cm square cube of water 1 kg 2,257,000 Joules ≈ energy to lift 225,700 kg or 507,000 lb 1 m


Energy Transfer by Water: Energy Transfer by Water Latent Heat Energy needed to change phase (substance remains at same temperature) Absorbed by surface water Released by water condensing to clouds


Energy Absorbed by Atmosphere: Energy Absorbed by Atmosphere 20% from Sun 7% conducted from surface 23% transferred by water 8% radiated by surface % of total insolation


Energy Emitted by Atmosphere: Energy Emitted by Atmosphere 30% reflected directly to space % of total insolation 58% emitted as IR


Complete Energy Budget: Complete Energy Budget


Global Warming: Global Warming


Venus: Greenhouse gone wild!: Venus: Greenhouse gone wild! The difference between Earth and Venus!


Temperature Controls: Temperature Controls Sunlight heats land, water, air Land warms, heats air Air circulates Convection cells warms -> expands -> rises cools -> contracts -> sinks Water circulates Currents driven by wind & Earth rotation Water temperature increases SLOWLY Large energy change needed for small temp. change


Convection Cells: Convection Cells Hot surface heats air Air expands, becomes less dense than surroundings rises, spreads out at top Air aloft cools, becomes more dense than surroundings sinks, spreads out on surface


Atmospheric Circulaton: Atmospheric Circulaton Rising Air Cools Water vapor condenses (usually) results in clouds Lowers surface pressure


Atmospheric Circulaton: Atmospheric Circulaton Falling Air Warms DRY (lost mosture rising) Increases surface pressure


Atmospheric Circulation: Atmospheric Circulation Sunlight heats ground Ground heats air , drives convection from subsolar latitude Subsolar latitude is 23.5º N/S on the solstices Subsolar latitude is 0º on the equinoxes


Atmospheric Circulaton : Atmospheric Circulaton Air rises from subsolar latitude, clouds form & precipitate, air aloft moves N & S, cools, dries & sinks at about 30º N & S Moist air rising  humid Dry air falling  Arid Air aloft cools until it sinks Air spreads N & S on surface Driven by heating near equator


Atmospheric Circulaton: Atmospheric Circulaton Air from aloft sinks near poles, moves N & S along surface Moist air rising  humid Dry air falling  Arid Surface flows converge, rise Air warms and moistens along surface Driven by cooling near poles Cold, dry air falling  Arid


Pressure Zones: Pressure Zones Rising Air: Low Pressure InterTropical Convergence Zone


Pressure Zones: Pressure Zones Falling Air: High Pressure


Pressure Zones: Pressure Zones Pressure Zones: air motion is vertical so there is little wind!


Wind Zones: Wind Zones Winds: Falling air spreads North & South along surface. But the winds don’t go straight!


Wind Zones: Wind Zones Winds named for direction they are from Windless zones names vary


General Atmospheric Circulation: General Atmospheric Circulation Cross sectional view ITCZ STHPC Easterly Trades Polar High Westerlies Polar Easterlies


World Pressure Cells: January: World Pressure Cells: January H North American High Parallel isobars over (low friction) ocean ⇒ rippin’ winds!!! Siberian High


World Pressure Cells: January: World Pressure Cells: January Parallel isobars over (low friction) ocean ⇒ rippin’ winds!!! Tibetan Low


Upper Atmospheric Winds: Upper Atmospheric Winds Jet Streams: Fast Winds Aloft Polar Jet Stream Above Polar Front (midlatitude air meets polar) Rossby waves move loops north & south 7,600 – 10,700 m (25-35 kf) speeds up to 300 kph (190 mph)


Upper Atmospheric Winds: Upper Atmospheric Winds Jet Streams: Fast Winds Aloft Subtropical Jet Stream above Subtropical highs (tropical air meets midlatitude) 9,100 – 13,700 m (30-35 thousand feet) speeds less than Polar Jet Stream


Polar Jet Stream: Polar Jet Stream Determines N.Am. winter weather Strong west wind monitored by weather balloons Check out PBS’s explanation!: www.pbs.org/wgbh/nova/vanished/jetstream.html


Polar Jet Stream: Polar Jet Stream Determines N.Am. winter weather Rossby waves bring cold air south