ATMOSPHERE HEATING RATE: CLOUD FREE ATMOSPHERE Words and Equation from Petty: Radiative Heating Rate Heating Rate Due to Absorption (positive) and emission (negative) by gases in the atmosphere. Cloud free atmosphere. (Wallace and Hobbs pg 139.) Solar radiation: Solid curves. Terrestrial radiation: Dashed curves. Heavy Black: Combined effect of solar and terrestrial radiation. Notes: Stratosphere near balance. CO2 cooling, O3 heating. Troposphere, water vapor dominates, with mostly IR cooling and some solar heating. BALANCE: Achieved by addition of latent and sensible heat from the surface. The surface is heated by absorption of solar and IR radiation. From Petty. Tropical Atmosphere. From Petty. Total heating, tropics, dependent on sun angle. From Petty. From Petty, dependence on geographical location. ATMOSPHERE HEATING RATE: CLOUDY ATMOSPHERE Schematic of Cloud Heating and Cooling Effects: Wallace and Hobbs Pg 139. IR cooling at cloud top and heating at cloud base tends to increase the lapse rate, promoting convection. Daytime heating by solar radiation heats cloud tops, suppressing convection. IR Cooling Rates (from Liou) Messages: Clouds are good absorbers and emitters of IR radiation. Solar heating most at cloud top, countering cloud top cooling in the IR, during day. Cooling rate is from the vertical divergence of the net irradiance absorbed and emitted. dFnet T cp dz t OVERALL RADIATION BALANCE: Increased solar absorption in troposphere (lowers albedo) -> increased IR from atmosphere to gnd, gnd to atmosphere, atmosphere to space (response to lowering albedo). Radiation Pathways and ‘Budget’ (342 W/m2 is the total Solar 1,370 W/m2 averaged over the Earths’ Surface) Radiative Balance: Wallace and Hobbs Ch10. 70 net absorbed 70 net emitted 100 units solar solar radiation = 342 W/m2. Black=Solar Radiation, Red = IR Radiation.