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University of Oslo (UiO) (2005)

Radiative forcing by changes in surface albedo caused by changes in vegetation

Kvalevåg, Maria Malene

Titre : Radiative forcing by changes in surface albedo caused by changes in vegetation

Auteur : Kvalevåg, Maria Malene

Université de soutenance : University of Oslo (UiO)

Grade : Master thesis in Geosciences Meteorology and oceanography 2005

Résumé
The human influence on vegetation causes changes in the surface reflective properties. By using MODIS land cover and MODIS surface albedo products, an estimation of radiative forcing due to surface albedo changes caused by vegetation changes is performed. A potential natural vegetation data set is used to compute radiative forcing estimates from pre agricultural times to present. A combination between MODIS blacksky and whitesky albedo and diffuse and direct radiation at ground level makes it possible to improve the accuracy of the present surface albedo. A new self-composed surface albedo data set is calculated for the purpose of not overestimating the radiative forcing in snow covered cropland regions. For that reason, a constraint on the pre agricultural data set is carried out by not allowing any surface albedo values to be lower than 0.081. The best estimate shows a radiative forcing due to the surface albedo change of -0.03 W/m2, which is weaker than what has been claimed earlier by previous studies. This is mainly because of a more realistic value of cropland, the albedo constraint, and also the intrinsic power of the method consisting of combining two MODIS products

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Page publiée le 11 octobre 2012, mise à jour le 13 février 2018