Shortwave radiation reflection

Estimates of albedo changes from data on the outgoing shortwave radiation reflected by the Moon (2000-2004) + 16... 

Fig. 18-3. Dense fog maintaining stability in a valley. It reflects shortwave radiation during the dav and radiates heat from the top of the fog at night. Source Adapted from Schrenk et...

This estimate of forcing can be compared with the estimate derived from the Earth Radiation Budget Experiment (ERBE) compared with a total absence of clouds on the Earth, the presence of clouds increases the global average reflection of shortwave radiation by about 50 Wm-2 (Hartmann 1993). 

Fig. 17-4. Radiation heat balance. The 100 units of incoming shortwave radiahon are distributed reflected from earth s surface to space, 5 reflected from cloud surfaces to space, 20 direct reaching earth, 24 absorbed in clouds, 4 diffuse reaching earth through clouds, 17 absorbed in atmosphere, 15 scattered to space, 9 scattered to earth, 6. The longwave radiation comes from (1) the earth radiating 119 units 101 to the atmosphere and 18 directly to space, and (2) the atmosphere radiating 105 units back to earth and 48 to space. Additional transfers from the earth s surface to the atmosphere consist of latent heat, 23 and sensible heat, 10. Source After Lowry (4).

Soil acts as an extremely important component in the energy balances of plants. For instance, shortwave irradiation can be reflected from the surface of the soil, it is the source of longwave radiation that can correspond to a temperature considerably different from that of the ambient air, and heat can be conducted to or from stems in the region of their contact with the soil. Also, considerable amounts of energy can be stored by the soil, in contrast to the case for most leaves. Although the soil surface can have large daily oscillations in temperature (e.g., Fig. 7-13), the soil temperature at moderate depths of 1 m can be extremely steady on a daily basis (variations less than 0.1°C) and fairly steady seasonally. 

Not all this shortwave solar radiation reaches Earth s surface, however some is absorbed by the atmosphere and clouds, and some is reflected from the atmosphere and clouds back into space. When skies are clear, approximately 80-85% of the solar radiation reaches Earth s sruface when skies are cloudy, approximately 50% reaches Earth s surface. Earth s surface itself has an albedo that averages approximately 0.35. The amount of solar radiation received per unit of surface area also varies with the sine of the solar altitude (the angle between the sun and the horizon). Total shortwave solar radiation arriving on Earth s surface ranges from zero at night, to hundreds of watts per square meter when the solar altitude is moderate, to over a kilowatt per square meter under clear conditions when the sun is directly overhead. 

Approximately 350 W/m of solar radiation would be received at this hypothetical Earth s surface. The surface reflects approximately 35% of received radiation. Use the Stefan-Boltzmann law, Eq. (4.53), to solve for T, by equating the absorbed shortwave solar radiation to the rate of longwave radiation ... 

In addition to atmospheric gases and vapors, aerosols such as sulfate particles, black carbon, and SOA also influence the radiation balance of Earth. The net effect of particles is complex depending on their size, composition, and reflectivity, particles may both absorb and scatter shortwave and longwave radiation. Some particles may make a negative contribution to radiative forcing. For example, particulate emissions from Mt. Pinatubo in 1991 resulted in months of measurably lower surface temperatures. 

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