《环境化学》课程PPT教学课件讲稿（英文版）Unit 6 Particles and clouds

Particles and clouds

Particles and Clouds

Cloud albedo forcing: Cooling Shortwave Radiation The shortwave ays from the Sun are scattered in a cloud; many of the rays return to space. The resulting"cloud albedo forcing taken by itself, tends to cause a cooling of the Earth

Cloud albedo forcing : Cooling The shortwave rays from the Sun are scattered in a cloud; many of the rays return to space. The resulting "cloud albedo forcing”, taken by itself, tends to cause a cooling of the Earth

Cloud Greenhouse Forcing: Warming Longwave Radiation Longwave radiation EARTH When a cloud absorbs longwave radiation emitted by the earth's surface, the cloud re-emits a portion of the energy to space and a portion back toward the surface. This process is called"cloud greenhouse forcing"and taken by itself, tends to cause a heating or positive forcing" of the earth's climate

Cloud Greenhouse Forcing: Warming Longwave radiation When a cloud absorbs longwave radiation emitted by the Earth's surface, the cloud re-emits a portion of the energy to space and a portion back toward the surface. This process is called "cloud greenhouse forcing" and, taken by itself, tends to cause a heating or "positive forcing" of the Earth's climate

Overall effect of all clouds Cloud albedo forcing> cooling Cloud greenhouse forcing warming The overall effect of all clouds together is that the earth 's surface is cooler than it would be if the atmosphere had no clouds The dominate factor in the global albedo is clouds

Overall effect of all clouds • Cloud albedo forcing → cooling • Cloud greenhouse forcing → warming • The overall effect of all clouds together is that the Earth's surface is cooler than it would be if the atmosphere had no clouds • The dominate factor in the global albedo is clouds

Aerosol: definition Aerosol is a suspension of solid or liquid particles in a gas Atmospheric aerosols consist of small particles of liquid and solid material suspended in the air Bioaerosol: An aerosol of biological origin. (Examples viruses, bacteria, fungi, spores, and pollens. Aerosol sizes are usually measured in the unit of micrometer (um) um =10- m 1 um=104 angstrom(A)

Aerosol: Definition • Aerosol is a suspension of solid or liquid particles in a gas. • Atmospheric aerosols consist of small particles of liquid and solid material suspended in the air. • Bioaerosol: An aerosol of biological origin. (Examples: viruses, bacteria, fungi, spores, and pollens.) • Aerosol sizes are usually measured in the unit of micrometer (mm) – 1 mm = 10–6 m – 1 mm = 104 angstrom (Å)

Typical Particle Diameters (um) Photochemical aerosols 0.01-1 Tobacco smoke 0.25 Coal fly ash 1-50 Flour dust 15-20 Pollens 15-70 Human hair: 25-100 um

Typical Particle Diameters (mm) Photochemical aerosols 0.01-1 Tobacco smoke 0.25 Coal fly ash 1-50 Flour dust 15-20 Pollens 15-70 Human hair: ~25-100 mm

Example images of atmospheric particles Sourcehttp://www.mpch-mainz.mpg.de/-kosmo/

Example images of atmospheric particles Source: http://www.mpch-mainz.mpg.de/~kosmo/

Aerosol sources Windblown Clouds and Dust sO? from Precipitation volcanoes Soot and Smoke Salt from Sea Spray an Bursting Bubbles Desert and volcanoes se Ocean* Fossil Fuels and Biomass Burning

Aerosol sources

Aerosol sources Windblown dust from desert Sulfate aerosol from volcano eruption fuel combustion and microbial activities Seasalt aerosol from seaspray and bubble bursting Soot from fuel combustion Secondary organic aerosol from volatile organic compounds

Aerosol sources • Windblown dust from Desert • Sulfate aerosol from volcano eruption, fuel combustion and microbial activities. • Seasalt aerosol from seaspray and bubble bursting • Soot from fuel combustion • Secondary organic aerosol from volatile organic compounds

Aerosol Radiative Forcing: direct effect The effect of aerosol on the energy flux of the atmosphere depends on particle size and composition Dark particles(soot-containing) tend to absorb light, thus warming Earth's atmosphere Small particles tend to scatter light, thus increasing the albedo of the atmosphere

Aerosol Radiative Forcing: direct effect • The effect of aerosol on the energy flux of the atmosphere depends on particle size and composition. – Dark particles (soot–containing) tend to absorb light, thus warming Earth’s atmosphere. – Small particles tend to scatter light, thus increasing the albedo of the atmosphere