III Circulation of the Atmosphere A Atmosphere Weather and Climate Some history All cultures recognize impacts of climate and want to predict and influence the weather Formal study of the atmosphere goes back to the Greeks Aristotle s treatise Meteorologica discourse on things above III Circulation of the Atmosphere A Atmosphere Weather and Climate Some history Initially humans most interested in extremes of weather drought flood violent storms More recently we are interested in how industrial activity influences weather and human health III Circulation of the Atmosphere A Atmosphere Weather and Climate Some historical examples Dec 1952 London fog Los Angeles in the late 1950s III Circulation of the Atmosphere A Atmosphere Weather and Climate Some historical examples Local problems original solutions Time release of pollutants with storms Build taller smokestacks To understand how human activity might Effective but usingweather the atmosphere as influence locally the atmosphere and an infinite to regional not problems climate wesewer need led to understand only its acid rain GHG ozone depletion structure but why and how it moves III Circulation of the Atmosphere A Atmosphere Weather and Climate Atmosphere Gaseous layer from Earth s surface to the edge of space Weather For us Troposphere Stratosphere State ofTropopause the atmosphere at a particular place or region for a short period of time Climate Average weather for a place or region Usually average of last 30 years III Circulation of the Atmosphere A Atmosphere Weather and Climate B Origin of the Atmosphere Earth s early atmosphere very different than today s Dense 10 of Earth s mass and composed of CO H2S N2 H2 H20 All was lost to the intense solar wind during earliest episode in Earth s history Present atmosphere Derived from outgassing of Earth s hot interior Initially different in composition from the modern atmosphere Solar wind removes initial atmosphere III Circulation of the Atmosphere A Atmosphere Weather and Climate B Origin of the Atmosphere Why doesn t the atmosphere just drift off into space Some of it does but its only the lightest gases hydrogen H2 and helium He2 The rest is held in place by gravity III Circulation of the Atmosphere A Atmosphere Weather and Climate B Origin of the Atmosphere C State of the Atmosphere a Composition nearly constant b Temperature Pressure Humidity c Winds III Circulation of the Atmosphere D Movement of air 1 Vertical motion 2 Horizontal motion IV Circulation of the Atmosphere D Movement of air 1 Vertical motion buoyancy density 2 Horizontal motion Air moves horizontally because of differences in pressure Air always moves from high pressure to low pressure Rate of movement wind speed depends on the pressure gradient III Circulation of the Atmosphere D Movement of air 1 Vertical motion buoyancy density 2 Horizontal motion differences in pressure 3 The Heat Engine a Sea Breeze a simple heat engine b The Earth as a heat engine Flux of solar radiation less at higher latitudes max at equator Sun Earth III Circulation of the Atmosphere D Movement of air 4 The Coriolis Effect Tendency for fluids air or water or anything moving in them moving across Earth s surface to be deflected from a straight line path Not a real force III Circulation of the Atmosphere D Movement of air 4 The Coriolis Effect Coriolis Rules of thumb NH to right SH to left Effect is small cannot impact draining bathtub etc Biggest effect is on large objects Impact increases as speed of object increases Coriolis Effect is zero at the equator III Circulation of the Atmosphere 5 General Circulation of the Atmosphere a Hadley Cell 0 to 30 on either side of the equator b Ferrel Cell Indirect 30 to 60 on either side of the equator c Polar High or Polar Easterlies 60 90 ITCZ Inter Tropical Convergence Zone Doldrums Horse Latitudes Tropical Easterlies Mid latitude Westerlies Polar Easterlies IV Circulation of the Atmosphere 5 General Circulation of the Atmosphere d Consequences of large scale circulation Distribution of major deserts dust Distribution of rainfall Average zonal winds Trades Westerlies III Circulation of the Atmosphere 6 Seasonal contrasts Because Earth s axis is tilted relative to its orbit around the Sun we have seasons III Circulation of the Atmosphere 6 Seasonal contrasts Maximum flux of solar radiation shifts north and south of the equator over the annual cycle This exerts a powerful influence on atmospheric circulation imparting a strong seasonal cycle over the large scale patterns of atmospheric motion III Circulation of the Atmosphere 6 Seasonal phenomena a Temperature Continentality range of temperature during a seasonal cycle Tied to the different properties of land vs ocean just like our sea breeze analogy Albedo Heat capacity Convection water vs Conduction solids III Circulation of the Atmosphere 6 Seasonal phenomena a Temperature Continentality range of temperature during a seasonal cycle Tropical regions and maritime regions coastal have low continentality Mid latitude large continents have high continentality Poles are lower III Circulation of the Atmosphere 6 Seasonal phenomena b Hurricanes Atlantic Typhoons in the Pacific Cyclones in the Southern Hemisphere They are all the same thing SAFFIR SIMPSON DAMAGE POTENTIAL SCALE CATEGORY 1 2 3 4 5 WINDSPEED MPH 74 95 96 110 111 130 131 155 155 PRESSURE MB 980 965 979 945 964 920 944 920 SURGE FT 4 5 6 8 9 12 13 18 18 15 km 500 km IV Circulation of the Atmosphere 6 Seasonal phenomena b Atlantic Hurricanes How and where do they start Evaporation rate IV Circulation of the Atmosphere 6 Seasonal contrasts b Atlantic Hurricanes Start As small low pressure disturbances off Africa Require Warm water 26 C High evaporation rates Stable troposphere to develop the spiral keeps them over warm water Track that To provide fuel through the release The rate of evaporation from the of latent related heat ofto condensation ocean is exponentially The role of water vapor in hurricanes Release of latent heat is THE primary fuel that intensifies hurricane winds Without latent heat there would be no hurricanes Cloud Motion LOW pressure Northern Hemisphere Cloud Motion LOW pressure Southern Hemisphere IV Circulation of the Atmosphere 6 Seasonal phenomena b Atlantic Hurricanes Prediction Start First Principles Basic circulation of the atmosphere Coriolis Why in Sept instead of July when hottest Will Global Warming cause more or stronger hurricanes The rate of evaporation from