Earths Energy Balance A global balance is maintained
Earth's Energy Balance A global balance is maintained by transferring excess heat from the equatorial region toward the poles
The Earth’s Orbit Around the Sun • Seasonally varying distance to sun has only a minor effect on seasonal temperature • The earth’s orbit around the sun leads to seasons because of the tilt of the Earth’s axis
Stability in the atmosphere An Initial Perturbation Stable Unstable Neutral If an air parcel is displaced from its original height it can: Return to its original height - Stable Accelerate upward because it is buoyant - Unstable Stay at the place to which it was displaced - Neutral
Energy associated with phase change Sublimation Deposition
Rain formation in warm (not frozen) clouds • In a supersaturated environment, activated cloud drops grow by water vapor condensation – It takes many hours for the cloud drop to approach rain drop size • Collisions between cloud drops can produce large rain drops much faster through coalescence – Collisions occur in part due to different settling rates of large and small drops – Not all collisions result in coalescence • Rain formation favored by – Wide range of drop sizes – Thick cloud – Fast updrafts
Forces Acting on the Air • Pressure gradient force (pushing) • Gravity (falling) • Friction (rubbing against the surface) • “Apparent” forces – The Coriolis Force – Centrifugal Force
Jet Streams • • Subtropical Jet is zonal mean response to poleward flow in upper branch of Hadley Cell Polar front jet is response to meridional temperature gradients
Summary of Cyclone Weather Roles of convergence and divergence aloft Pattern of clouds, precipitation, and temperatures on the ground
Global Projections of Surface Temp • Land vs ocean! B 1 • North vs South • Global mean warming of 2º to 5º A 1 B • North American warming of 3º to 6º C = 5º to 11º F • Arctic warming of 8º to 14º F A 2
“Satbilization Wedges” 16 Billions of Tons Carbon Emitted per Year p” 16 Gt. C/y am h at = “r Eight “wedges” tp en rr u C 8 Historical emissions Goal: In 50 years, same global emissions as today Flat path 1. 6 0 1950 2000 Courtesy of Rob Socolow, Princeton 2050 2100
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