Forest albedo

Another family of feedbacks involving biota arise via the process of evapotranspiration in which the rate of water vapor is transferred from the land surface to the atmosphere is mediated by plants. Several consequences have been proposed that include influences of biota on the greenhouse effect of water vapor as well as relative humidity and clouds. Lovelock (1988) suggested that tropical forests might be kept cool by increasing cloud cover in response to higher relative humidity released through enhanced evapotranspiration (via the clouds influences on albedo). Yet another connection arises because tree-covered land has different turbulence properties above it than bare soil, which also influences the cloud cover above. 

If we let Ti be the predictive temperature that we have now, 255 K, we can quickly see what happens if A changes from Ai, to a new value A2. The current albedo of Earth is ca. 0.3, and current fractional cloud cover is ca. 0.5. Ice and snow cover are minimal and most of the Earth is oceans with Aocean 0.1. Forests have forests 0.1 so most of the noncloudy Earth has. A % 0.1. This gives an expression for average cloud albedo ... 

Challenger F, Simpson M (1948) Studies on biological methylation. Part 12. A precursor of the dimethyl sulphide evolved by Polysiphonia fastigiata. Dimethyl-2-carboxyethylsulphonium hydroxide and its salts. J Chem Soc 3 1591-1597 Charlson RJ, Lovelock JE, Andreae MO, Warren SG (1987) Oceanic phytoplankton, atmospheric sulphur, cloud albedo and climate. Nature 326 655-661 Coley PD, Aide T (1991) Comparison of herbivory and plant defenses in temperate and tropical broad-leaved forests. In Price P, Lewinsohn T, Fernandes G, Benson W (eds) Plant-animal interactions evolutionary ecology in tropical and temperate regions. Wileys, New York, pp 25 19... 

Several steps in implementation of specific urban dynamics and energetics have already been achieved by the HIRLAM/HARMONIE community. Enviro-HIRLAM considers a surface improved description for urban areas roughness, albedo, urban heat sources (Eaklanov et al. 2008). Properties of urban aerosol used to modify the albedo characteristics and the effective radius of cloud droplets for the SW radiation (in the HIRLAM radiation scheme). In FUMAPEX two other more sophisticated urban schemes EEP (Martilli et al. 2002) and SM2-U modules (Dupont and Mestayer 2006) were tested. They are more expensive computationally. Town energy balance (TEE) module (Masson 2000) is a part of SURFEX, available in the HARMONIE framework. Handling of the finest-scale details of momentum fluxes in town (forest) canopy could be developed. 

Plants exert additional effects on weathering. The presence of forest trees tends to lower soil surface temperatures by shading the soil surface and reducing surface albedo (Kelly et al., 1998). Also, roots fracture mineral grains and increase soil porosity and permeability, which allows greater contact between soil solutions and minerals (April and Keller, 1990 Colin et al., 1992). 

The mean temperature of the Earth is a result of input of energy from the Sun and loss of energy by emission of radiation. The input of energy is a function of the reflectivity (albedo) of the Earth. Ice reflects 80-95% of incident light, dry grassland 30-40%, and a conifer forest 10-15%. Therefore,... 

The interface between the geosphere and the atmosphere at Earth s surface is very important to the environment. Human activities on the earth s surface may affect climate, most directly through the change of surface albedo, defined as the percentage of incident solar radiation reflected by a land or water surface. For example, if the sun radiates 100 units of energy per minute to the outer limits of the atmosphere, and the earth s surface receives 60 units per minute of the total, then reflects 30 units upward, the albedo is 50 percent. Some typical albedo values for different areas on the earth s surface are evergreen forests, 7-15% dry, plowed... 

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