Satellite-observed energy budget change of deforestation in northeastern china and its climate implications

Abstract

Large-scale deforestation may affect the surface energy budget and consequently climate by changing the physical properties of the land surface, namely biophysical effects. This study presents the potential energy budget change caused by deforestation in Northeastern China and its climate implications, which was evaluated by quantifying the differences in MODIS-observed surface physical properties between cropland and forest. We used the MODIS land products for the period of 2001-2010 in 112 cells of 0.75° × 0.75° each, within which only best quality satellite pixels over the pure forest and cropland pixels are selected for comparison. It is estimated that cropland has a winter (summer) mean albedo of 0.38 (0.16), which is 0.15 (0.02) higher than that of forest. Due to the higher albedo, cropland absorbs 16.84 W·m -2 (3.08 W·m -2) less shortwave radiation than forest. Compared to forest, cropland also absorbs 8.79 W·m -2 more longwave radiation in winter and 8.12 W·m -2 less longwave radiation in summer. In total, the surface net radiation of cropland is 7.53 W·m -2 (11.2 W·m -2) less than that of forest in winter (summer). Along with these radiation changes, the latent heat flux through evapotranspiration over cropland is less than that over forest, especially in summer (-19.12 W·m -2). Average sensible heat flux increases in summer (7.92 W·m -2) and decreases in winter (-8.17 W·m -2), suggesting that conversion of forest to cropland may lead to warming in summer and cooling in winter in NortheasternChina. However, the annual net climate effect is not notable because of the opposite sign of the energy budget change in summer and winter.