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Albedo

Based on satellite observations of the African continent, this animation shows the surface albedo (the reflectivity of a surface) for 1981 to 2005 and, at the same time, the temporal evolution of climatological albedo anomalies for the Sahel.

For the cloud free earth, the albedo is a measure for the optical brightness of the surface. It is defined as the coefficient between the reflected radiation and the total incoming sunlight. Thus, the albedo can take values between 0 (no reflectance at all) and 1 (100% reflectivity).
The albedo of a land surface is mainly governed by the color and structure of the soil and by the vegetation. The latter factor varies regularly due to the annual cycle. Furthermore, weather or climate anomalies induce variations of the vegetation and, hence, albedo on longer time scales.

 

In this animation, the albedo for the continent of Africa is shown for the period from 1981 to 2005. The white frame denotes the Sahel region, for which the albedo anomaly relative to the climatological mean is shown in the display on the right side. Periods with more severe drought cause reduced plant growth and, hence, larger albedo values – shown here in red colors. Accordingly, here blue colors show periods with enhanced productivity.
The severe Sahelian drought in the 80's is clearly visible in the dataset in a brightening of the surface due to reduced vegetation cover. The dataset allows for the quantification of the drought-related albedo changes in this vulnerable area.
The data set used for this work features a unique compilation of the surface albedo on the basis of data from the Meteosat first generation satellites. At the MPI-M, the data set was enhanced with respect to the temporal consistency (for details see Loew and Govaerts, 2010). The original satellite data were acquired by EUMETSAT.


More Information:

Contact at MPI-M: Alexander Loew

Original data via EUMETSAT-Archive

 

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