基于GLASS数据估算中国陆表净辐射及其空间分布分析

Land surface radiation budget parameterization and spatial analysis over China using GLASS data

地表辐射收支是能量循环的重要参数,影响着地球水热平衡,是全球气候变化研究的重要方面。多数研究利用MODIS数据估算地表辐射收支,模型输入参数复杂。综合利用GLASS数据、MODIS数据和地面实测数据,采用Bisht等提出的净辐射估算方法,制订一种简单的地表辐射收支估算方案,分别计算2010年1-12月中旬卫星过境时刻中国陆表净辐射的最大值。通过改进的正弦模型将估算结果转换为日最大地表净辐射,并利用地面实测日最大净辐射值对估算结果进行了验证。研究表明:综合利用GLASS数据、MODIS数据和地面实测数据建立的地表辐射收支模型能够很好地模拟中国陆表净辐射的分布,与地面实测日最大净辐射值具有较好的一致性,平均误差为27.21 W?m-2,克服了利用其他遥感数据估算地表辐射收支输入参数复杂,数据量大的缺点,适用于大尺度地表陆表辐射收支研究。

Land surface radiation is an important parameter with regard to energy cycling and global water- heat balance. Estimating land surface radiation is a significant part of global climate change research. Series of remote sensing data have been used in the calculation of each parameter of the land surface radiation budget. The MODIS data are widely used, but the schemes are complicated. How to estimate land surface radiation easily and accurately is always an appropriate subject of debate. The GLASS data were published by Peking University in 2012 and can be directly used in global change research. Firstly, GLASS data（including albedo data, land surface emissivity data and downward shortwave radiation data）, MODIS land surface temperature data and ground observed data were employed to develop a modified parameterization scheme of net radiation based on the research published by Bisht et al. in2005. The maximum net radiation over eight continuous days in the middle of each month in2010 was calculated using the scheme presented in this paper. Because the values that were obtained at the time of the satellite passing by were instantaneous, the instantaneous values were translated into the daily maximum data using the modified sinusoidal model and validated using ground observed data. There was a good agreement between ground observed data and the parameterization results and the average bias was 27.21 W ？ m-2. The results showed that the scheme presented in this paper was an effective model to calculate land surface radiation over China. Our scheme required less input data. It can be applied to calculate land surface radiation at the scale of a large region. The spatial pattern change over China in 2010 was also analyzed.The results show that the land surface radiation changes significantly with the seasons and there are differences between different places at the same time. Generally, the value of net radiation increases in the first eight months and decreases in the last four months. The maximum net radiation gradually decreases from south to north. The probable reason is the different characters of the underlying surface, including land cover and geographic location.