Mapping high-resolution land surface radiative fluxes from MODIS: Algorithms and preliminary validation results

Land surface radiative fluxes are needed to address a variety of scientific and application issues related to climate changes, hydrologic and biogeophysical modeling, solar energy applications, and agriculture. The Earth's surface radiation budget (SRB) is the key quantity that determines global climate and climate change from elevated greenhouse gases, air pollution (Wang K. et al. 2009), and land cover and land use changes (Wang et al. 2007b). The SRB is also important to life and to the use of clean renewable solar energy to improve the quality of the environment. Altering surface radiation force will lead to a significant adjustment in surface temperature, moisture, and fluxes during the consequent complex land surface thermodynamic and hydrological processes. It affects the surface heat and moisture budget as well as biological productivity. The observed reduction in land surface radiation over the last several decades (1960-1990), the so-called dimming effect, and the more recent evidence of a reversal in dimming over some locations beyond 1990 suggest several consequences on climate, notably on the hydrological cycle (Liepert and Romanou 2005, Wild et al. 2005, 2007). Such a reduction in radiation should imply reduced surface temperature and precipitation. Overestimation of the incoming solar radiation over land has major impacts on the climate over land (Betts et al. 1996, Dickinson 1995, Garratt et al. 1993). Viterbo and Beljaars (1995) found that excessive net radiation at the surface forced excessive surface evaporation, and dried out the soil moisture during data assimilation in the ECMWF (European Centre for Medium-Range Weather Forecasts) global model.