Abstract: Based on radiation data observed at Xilinhot National Climatological Observatory of Inner Mongolia in 2010, the diurnal and seasonal dynamics of surface radiation balance and albedo over typical semi-arid grassland in Inner Mongolia was analyzed and compared with those in arid area of northwest China in this paper. The radiation data was measured by CNR-1（Kipp & Zonen），a four components radiation sensor of the benchmark radiation observation system. Output data was processed to the mean value of 30 minutes in analysis. In order to control the quality of data, the probable value, the extreme value and the relationship between different radiation components were checked carefully in accordance with the standard proposed by the Basic Surface Radiation Network（BSRN）. The results of this paper indicated that: the seasonal variation of global radiation over semi-arid grassland was quite evident. The annual total of global radiation reached about 6 036.64 MJ/m2，which was lower than that observed from gobi and desert and close to that in oasis. The monthly variation tendency of surface reflected radiation was relatively complicated. The monthly mean values of surface reflected radiation in semi-arid grassland from April to October were smaller than those in grassland and desert of Heihe Basin and larger than those in cropland due to diversity of surface vegetation and soil humidity. The seasonal variation of surface absorptive radiation accorded with that of global radiation. The annual total of atmospheric long-wave radiation was lower than that over different surface of Heihe Basin on account of the lower annual mean temperature and higher latitude in semi-arid grassland. The total value of surface long-wave radiation in semi-arid grassland form June to September was about 4 532.14MJ/m2，which was larger than that in grassland and cropland and smaller than that over desert. The annual total value of surface effective radiation was up to 2 398.75 MJ/m2，which was higher than that in oasis and lower than that in desert and oasis. Since the durations of surface snow cover over semi-arid grassland in Winter and Spring were longer than those in arid area, the annual mean value of surface albedo in semi-arid area reached about 0.35, which was all higher than that on different surface in arid area. This shows that the surface snow cover has a significant effect on surface albedo.

Key words: Inner Mongolia； , semi-arid grassland； , surface radiation； , diurnal variation； , seasonal distribution