Albedo, definition

Climate is often viewed as the aggregate of all of the elements of weather, with quantitative definitions being purely physical. However, because of couplings of carbon dioxide and many other atmospheric species to both physical climate and to the biosphere, the stability of the climate system depends in principle on the nature of feedbacks involving the biosphere. For example, the notion that sulfate particles originating from the oxidation of dimethylsulfide emitted by marine phytoplankton can affect the albedo (reflectivity) of clouds (Charlson et ai, 1987). At this point these feedbacks are mostly unidentified, and poorly quantified. 

Snow is a porous medium formed of air, ice crystals and small amounts of chemical impurities. Because ice has a high vapor pressure (165 Pa at -15°C, 610 Pa at 0°C), the vertical temperature gradient that is almost always present within the snowpack generates sublimation and condensation of water vapor that change the size and shape of snow crystals. This results in changes in physical variables such as density, albedo, heat conductivity, permeability and hardness. These physical changes have formed the basis for the definition of snow metamorphism. ... 

We will demonstrate later that the transmission coefficient (or transmittance, cf. Sec. 5.3a) is identical, from a physical standpoint, with our previous definition of the albedo [cf. Eq. (5.111)]. It is appropriate, then, to use the same symbol. 

In this definition, the two edges of the HZ (see Fig. 5.3), depend on the Bond albedo of the planet. A, the luminosity of the star, the planet s semi major axis, D, as well as the eccentricity, e, of the orbit, and in turn the average stellar irradiation... 

A determination of the planetary albedo requires a large set of individual photometric measurements. Two approaches may be followed in collecting the data. In one approach the flux from a surface element is determined by recording the intensities emanating from that element in all directions and calculating the local flux according to the definition (Chandrasekhar, 1950),... 

Figure 1 illustrates the structure of the model. Refer to the list of symbols for definitions. The low latitude cell (latitude below TON, subscript 1) and the polar cell (subscript 2) have surface temperatures Tj, relative surface areas gi, surface albedos a, incoming solar radiation at the surface Fi, ospheric longwave emissivity parameter P, explained below, and poleward heat advection Dj. The two surface temperatures are die dependent variables of the model. Denote die area weighted average of any quantity Q by = giQi + gzQzt and let AQ = Q1-Q2 denote Ae meridional contrast. 

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