Effects Of Spatio-temporal Changes Of Snow Cover On The Surface Radiation Budget In Heilongjiang Basin

Land use and land cover change(LUCC), an important driving force to climate change has become the focus of the global environment change research and GLP(global land plan). Since the global change proposed, people are paying more and more attention on the impacts of regional differences and spatio-temporal changes on the natural environment and the social and economic sustainable development, taking into account the variability and complexity of global changes at different spatial and temporal scales. However, at the regional scale, the mechanism of LUCC influencing ecological and climate system through biogeophysical process is not yet clear. Currently, the climate effects of land cover changes in low-latitude and high-latitude regions has made important progress, while the impact of land cover changes in mid-latitudes on climate needs further study. With the intensification of global warming, the snow cover variability is most obvious in mid-latitudes. The changes of snow cover will directly affect the surface water, heat and radiation balance, becoming the key component of land-climate feedbacks in mid-latitudes. This article selected the impacts of snow cover changes on surface radiation budget as the research object and chose the Heilongjiang Basin as the study area. First, this study build the Northern Hemisphere snow cover database in the nearly 50 years, with the trend analysis showing that the snow cover area decreased before 1990 and increased after that. Second, we built the albedo and emissivity database from 2000 to 2013 using MODIS products. We found that the two parameters had significant seasonal and internal variation which correlated to land cover and snow cover changes significantly. On this basis, combining with the land cover data and surface data we established a mapping database including the relationship between snow cover changes and surface parameters like albedo. Based on the relationship database and the history land cover and snow cover maps we rebuild the surface parameter database at the pixel scale at the historical periods. Next, an estimation model was used to assess the radiative forcing to the climate system caused by snow cover changes from 1980 to 2000 and 2000~2010 in Heilongjiang River. The results showed that the radiative forcing caused by the snow cover changes was larger than the land cover changes and the value was different at different time periods. Finally the WRF model was used to simulate the influences of snow cover changes on the surface radiation budget and heat balance. In the simulation, the reasonable choice of the land surface scheme and the localized surface parameter data improved the accuracy. The analysis of the surface variables showed that unlike other land cover types, snow cover had a more intense effect on the surface energy balance, which emphasized the importance of snow cover changes in the surface-atmospheric feedback system from another perspective. This study is very important for understanding the energy feedbacks of the climate system in mid latitudes.