Albedo solar radiation

In addition to biogeochemical cycles (discussed in Section 6.5), the hydrosphere is a major component of many physical cycles, with climate among the most prominent. Water affects the solar radiation budget through albedo (primarily clouds and ice/snow), the terrestrial radiation budget as a strong absorber of terrestrial emissions, and global temperature distribution as the primary transporter of heat in the ocean and atmosphere. 

Another family of feedbacks arises because the radical differences in the albedo (reflectivity) of ice, snow, and clouds compared to the rest of the planetary surface, which causes a loss of the absorption of solar radiation and thereby cools the planet. Indeed, the high albedo of snow and ice cover may be a factor that hastens the transition into ice ages once they have been initiated. Of course, the opposite holds due to decreasing albedo at the end of an ice age. As simple as this concept may appear to be, the cloud-albedo feedback is not easy to quantify because clouds reflect solar radiation (albedo effect) but absorb... 

The albedo of earth surface varies from about 0.1 for the oceans to 0.6-0.9 for ice and clouds which mean the clouds, snow and ice are good radiation reflectors while liquid water is not. In fact, snow and ice have the highest albedos of any parts of the earth s surface Some parts of Antarctic reflect up to 90% of incoming solar radiation. 

Their ability to reflect solar radiation (albedo) and... 

The albedo (R) of a thick, boundary layer cloud that does not absorb solar radiation over a surface with zero albedo can be approximated (Twomey, 1991 Schwartz and Slingo, 1996 Baker, 1997) by... 

Typical cloud albedos for thick clouds in the boundary layer are 0.5 over the ocean in midlatitudes i.e., half of the incoming solar radiation is scattered back out to space (Baker, 1997). This approximation, Eq. (JJ), illustrates why a change in the number of cloud droplets and their size affects the cloud albedo and hence the radiative forcing (see Problem 9). 

The aerosols of sulfuric acid so formed increase the reflectivity (albedo) of the Earth s atmosphere, cutting down the solar radiation that reaches the Earth s surface and so counteracting to some extent the greenhouse warming due to CO2 emissions that accompany the SO2, as mentioned earlier. Airborne sulfuric acid may be neutralized by traces of ammonia in the air, giving particulate NH4HSO4 and (NH4)2S04 hazes, but in the absence of such neutralization the aqueous sulfuric acid droplets in tropospheric clouds may reach pH 1.5 or lower. 

Surface compositions of icy satellites can be observed by reflection spectroscopy (UV to near-IR 0.2-5 pm) [5J. The physical properties and surlace compositions of icy bodies are summarized in Table 9.4. Major satelhtes of Jupiter (except for lo), Saturn, and Uranus show clear evidence of H2O ice (ice I) on Oieir surfaces. Altliough physical properties, such as density, radius, albedo, and surface structure of tlrese satellites differ greatly, they share basic compositional similarity. It is thus assumed that the ice of these satellites is pure H2O when we discuss Oieir internal structiue. The large spectral differences among satellites reflect surface modification histories by impact, volcanism, tectonics, and solar radiation. It is noted that SO2, O2, and O3 are trace components and contaminants. No NH3 or CH) ices, predicted by the equilibrium condensation theory, have yet been detected on these satellites. 

Here, t e is the reflectivity of the earth s surface for short wave radiation originating from the sun it is also known as the Albedo in meteorology. t e can be calculated from information about the absorptivity of solar radiation, given in the following section 5.4.5. The reflectivity of the atmosphere is indicated by rAti it is small and, according to [5.42], can be calculated from... 

Qo is the solar radiation at the top of the atmosphere and Tu = 0.95 is the transmissivity of the upper atmosphere. The albedo a is calculated from the Fresnel formula (Kondratyev, 1969). The quantities Tr and Ab are transmissivity and absorption in the atmospheric boundary layer. 

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