Albedo planets

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... 

Consider the amount of radiation arriving on the surface of the Earth at a distance of 1 AU or 1.5 x 1011 m. The total flux of the Sun is distributed evenly over a sphere of radius at the distance of the planet, d. From the luminosity calculation of the Sun, F, the solar flux at the surface of Earth, FEarth, is F/47t(1.5 x 1011)2 = 1370 Wm-2 from the least-square law of radiation discussed in Example 2.4 (Equation 2.4). Substituting this into Equation 7.6 with the estimate of the albedo listed in Table 7.2 gives a surface temperature for Earth of 256 K. 

Dry air rising in the atmosphere has to expand as the pressure in the atmosphere decreases. This pV work decreases the temperature in a regular way, known as the adiabatic lapse rate, Td, which for the Earth is of order 9.8 Kkm-1. As the temperature decreases, condensable vapours begin to form and the work required for the expansion is used up in the latent heat of condensation of the vapour. In this case, the lapse rate for a condensable vapour, the saturated adiabatic lapse rate, is different. At a specific altitude the environmental lapse rate for a given parcel of air with a given humidity reaches a temperature that is the same as the saturated adiabatic lapse rate, when water condenses and clouds form Clouds in turn affect the albedo and the effective temperature of the planet. Convection of hot, wet (containing condensable vapour) air produces weather and precipitation. This initiates the water cycle in the atmosphere. Similar calculations may be performed for all gases, and cloud layers may be predicted in all atmospheres. 

Calculate the effective surface temperature of an Earth-like planet with the same diameter, albedo and orbital radius around Aldeberan in Taurus, which has a surface temperature of 7200 K. Is the planet within the habitable zone of this star ... 

The reflection spectrum of the atmosphere is a measure of the albedo of the planet (Figure 10.4) and, despite the strong methane absorption in the red, Titan s disc looks orange principally due to scatter from the surface of dense methane-hydrocarbon clouds. Scatter from aerosol particles within the thick clouds obscures the surface of the moon although the radar analysis reveals considerable Chapman layer structure within the atmosphere and some interesting surface features. 

Compare our planet with Venus in terms of albedo, green house coefficient, and temperature. 

McEwen A. S. (1986) Exogenic and endogenic Albedo and color patterns on Europa. J. Geophys. Res. Solid Earth Planets 91, 8077-8097. 

Figure 1 The habitable zone (Kasting et al, 1993). Too close to the Sun, a planet s surface is too hot to be habitable too far, it is too cold. Early in the history of the solar system, the Sun was faint and the habitable zone was relatively close 4.5 Ga later, with a brighter Sun, planets formerly habitable are now too hot, and the habitable zone has shifted out. Note that boundaries can shift. By changing its albedo and by altering the greenhouse gas content of the air, the planet can significantly widen the hounds of the hahitahle zone (Lovelock, 1979, 1988).

Albedo - The ratio of the light reflected or scattered from a surface to the intensity of incident light. The term is often used in reference to specihc types of terrain or to entire planets. Alcohols - Compounds in which a hydroxy group, -OH, is attached to a saturated carbon atom. [5]... 

Albedo ratio of the light reflected from the planet to the light incident on it... 

Planet Dist. to sun ua Ecliptic angle Inclin. Orbit period (yr) Rotation period (hr) Albedo No. of satellites... 

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