Albedo changes ? Surface surveillance from satellites

Abstract

Natural changes in surface (and particularly land surface) albedo are described in terms of their impact upon climate. Emphasis is placed upon the importance of the regional or 'synoptic' scale view of albedo change and upon a methodology of monitoring such variations using current satellite surveillance. A case study of the United Kingdom during the 1976 drought reveals the large scale changes in reflectivity that can occur during extreme events. It is possible that such surface changes could have caused positive feedback in the atmospheric circulation thus prolonging the drought conditions.The understanding of natural climatic variability has taken on new urgency in our times (Schneider and Dickinson, 1974)

The climatic impact of a Sonoran vegetation discontinuity

“…In some areas of the world, and in particular in Sub-Saharan Africa, vegetation change has been suggested as a potential feedback mechanism for prolonging and intensifying drought. Although other processes (e.g., the role of evapotranspiration changes) are undoubtedly involved (Hare, 1977(Hare, , 1985Kidson, 1977;Barry, 1978;Lamb, 1978;Henderson-Sellers, 1980;Nicholson, 1983;Henderson-Sellers and Gornitz, 1984;Lockwood, 1986), increasing albedo with decreasing vegetation cover has been suggested as a contributor to the desertiflcation process. Whether cooling would occur in a desert environment of decreasing vegetation coverage has been argued since the publication of Charney's (1975) research.…”

Surface albedo data for climatic modeling

“…The fact that the zone boundaries are closely correlated is reassuring. The much higher values obtained byHenderson-Sellers [1980] are primarily the result of persistent drought conditions throughout the summer of 1976. Additionally, the differing wavelength regions and atmospheric effects give rise to quantitative differences in derived "albedo" values.It is worth noting that the satellite-derived map is drawn from one of the very few images for this area which is not contaminated by cloud!…”

“…This, however, requires accurate knowledge of the wavelength dependent albedo of the underlying surface and careful preselection of the wavelength channels of the radiometer on the satellite. To date, remotely sensed data have been applied only to small-scale surface albedo retrieval [e.g., Otterman, 1977a] or to medium-scale clear-sky (system) albedo variability [Kukla and Kukla, 1974;Rockwood and Cox, 1978;Henderson-Sellers, 1980].…”

“…used aircraft measurements of clear-sky (system) albedos to calibrate a precategorized vegetation/soil map. The albedo zonation map from Henderson-Sellers [1980] was drawn up from a NOAA advanced very high resolution radiometer (AVHRR) image of the United Kingdom. The fact that the zone boundaries are closely correlated is reassuring.…”

Influence of landscape structure on local and regional climate

“…While not intending to represent the actual earth's atmospheric response, this simple energy balance analysis is presented to illustrate the sensitivity of the earth's climate to even very small changes in land use. Henderson-Sellers (1980) and Henderson-Sellers and Gornitz (1984) present two examples of preliminary aThe smaller number is for high solar zenith angles, while the larger albedo is more representative for low sun angles. bFrom Sellers (1965:21).…”