Ch 4 Atmosphere and Surface Energy Balances Wednesday September 17 2014 4 13 PM A vast flow of energy cascading through Earth systems Changing seasons Daily weather conditions Earth s variety of climates Energy Pathways Input solar radiation insulation Net Energy Output heat Solar Energy unevenly distributed fluctuates seasonally Interception Land water Clouds Atmospheric gases Dust Weather Patterns Oceanic currents Vegetation distribution Energy Pathways and Principles Transmission Energy traveling through the atmosphere or the water Budget of our atmospheric energy input output Input shortwave ultraviolet visible near infrared Output longwave thermal infrared Atmospheric gases and dust interaction with insolation Scattering Diffuse Radiation Insolation Increasing density of atmospheric gases Gas molecules change in direction of light without wavelength alteration 7 of Earth s reflectivity albedo Further scattering Dust particles pollutants ice cloud droplets water vapor Why is the Earth s sky blue Rayleigh scattering gives the atmosphere its blue color Scattering by particles smaller than the wavelength of light Causes diffuse sky radiation The shorter the wavelength the greater the scattering Smog and haze white sky Larger particles in the atmosphere scatter all wavelengths of visible light Sunset and Sunrise Thickness of the atmosphere since the sun is at 0 degrees at sunrise and sunset Oblique angle rays longer travel time shorter wavelengths like blue have already scattered or bounced off in numerous directions Refraction bending action From one medium to another Space atmospheric gases air water Change in speed and shift in direction ex glass of water with pencil in it two major mediums are the air and the water the pencil appears to be in two pieces When visible light passes through a myriad raindrops Prism bending different wavelength to different angles separating the light into its component colors Sun s Refraction Mirage When the light waves are refracted by layers of air at different temperatures thus different density it appears higher in the sky A hot road mirage fake water on the road Insolation Single energy input Average annual insolation at the earth s surface Particular patters can be accounted by variation in surface features that impact insolation High insolation values are in the major deserts of the world in the tropics and subtropics Reflection Energy returned back into space without being absorbed Albedo Reflective quality intrinsic brightness of a surface of insolation that is reflected 0 total absorption 100 total reflectance lighter the color the higher albedo Color Darker colors lower albedo Lighter colors higher albedo On water surfaces angle of solar rays Lower angles higher albedo Higher angles lower albedo Roughness Smoother surfaces higher albedo Rough surfaces lower albedo Earth s average albedo is 31 July and January Albedos Average albedos of 19 38 for all surface between 23 5 N to 23 5 S January albedos are higher poleward of 40 N why More snow coverage snow has high albedo Tropical forest albedos are typically lower inalbedo 15 Clouds and Albedo and Greenhouse Forcing Clouds reflect the sun s rays which increases the albedo and cools Earth s surface Cloud Greenhouse Forcing Trap longwave radiation from Earth raise minimum temperatures The effect of particulates Mount Pinatubo Wind spread these aerosols worldwide The smoke from the fires and dust storms effects covered 42 of the globe in 60 days Atmospheric albedo increased 0 5 C cooling Aerosols and Albedo Industrialization Haze of pollution increased reflectivity of the atmosphere Atmospheric warming through absorption by pollutants about 50 Pollution dimmed sunlight reductions Global Dimming air pollution is believed to be the main cause Surface cooling through reduction in insolation by about 10 i e global dimming Above urbanized areas where large amounts of fossil fuels are burned Energy Pathways and Principles Absorption Assimilation of radiation by matter and its conversion from one form of energy to another 69 of insolation is absorbed Converted to infrared radiation Converted to chemical energy by plants in photosynthesis Raised the atmospheric temperature of absorbing surface Land and water surfaces 45 Gases dust clouds and stratospheric ozone 24 Heat Transfer Conduction Molecule to molecule Warmer to cooler Conductivity of the material Land surface is a better conductor than air Moist air is slightly better than dry air e g Heating of surface and overlying air Convection Transfer by movement Physical mixing involves a vertical motion Warmer masses tend to rise Cooler masses tend to sink WHY cooler masses are denser warmer masses are less dense Advection Horizontally dominant movement e g Horizontal movements of winds from land to sea and back Earth Atmosphere Radiation Balance 31 albedo 69 absorption Latent versus Sensible Heat Latent Heat energy transferred due to evaporation or condensation of water Sensible Heat Heat that we can sense A transfer of kinetic energy molecular motion Convection and conduction Energy Balance in the Troposphere The Earth thermal infrared wavelengths Absorbed by carbon dioxide water vapor methane nitrous oxide chlorofluorocarbons CFCs etc Emitted back to the Earth Delays the energy loss and cause warming in the troposphere Greenhouse effect e g Increasing carbon dioxide concentration Changes in the Earth atmosphere energy system Clouds and the Earth s Green House Clouds effect the heating of the lower atmosphere Cloud type height and thickness water content density etc transmission characteristics Jet Contrails Contrails form when hot humid jet exhaust is expelled into the cold Jet engine exhaust is hot up to 600 degrees Celsius Energy Budget for All Energy Energy imbalance Global circulation of energy and mass Agents winds ocean currents dynamic weather systems etc Radiation Budgets Latent heat LE latent heat of evaporation Sensible heart H through convection and conduction Ground heating and cooling G conduction Urban Environment Surface energy characteristics Similar to deserts Increasing urban population Effect A very dense environment where heat is trapped There is a lot of dust and particles in the air Pollutants increase the temperature as well Albedos of urban surfaces are lower Incoming insolation is caught Urban heat island Both maximum and minimum temperatures are higher than nearby rural settings What strategies would reduce the urban