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为了改进陆面模式对水文过程的模拟,地形指数水文模型（Topographic-index hydrologicalmodel,TOPMODEL）已被应用于陆面模式（Land Surface Models,LSMs）。当前直接将TOPMODEL应用于全球气候模式（Global Climate Model,GCM）的网格单元的方案,简化了TOPMODEL在陆面模式中的应用。按GCM网格单元统计与按流域单元统计的地形指数分布函数之间的差异大小进行分析,可为研究TOPMODEL与陆面模式耦合的合理简化方案提供依据。利用2°×2°网格的长江上游山区和地势较平坦的亚马逊地区并应用航天雷达地形测量资料的地形高程模型数据,计算了地形指数、均值和累积分布函数,并应用相同的地形高程数据提取网格中的流域和水系并计算了各流域的地形指数、均值和累积分布函数。在此基础上,分析了按整个网格计算的和按划分的流域计算的地形指数累积分布函数及其均值的差异,并用e指数函数拟合地形指数累积分布函数。结果表明：（1）以整个GCM网格为单元统计的与按流域为单元统计的地形指数累积分布函数及其均值存在差异,但差异并不大,将TOPMODEL直接应用于GCM网格单元的这种简化方案是可行的;（2）用e指数函数能够较好地拟合地形指数累积分布函数。“,”To improve simulations of hydrological processes,the topographic-index hydrological model(TOPMODEL)has been applied to land surface models.The simplified scheme which applies TOPMODEL to grid cells of Global Climate Model(GCM)can simplify application of TOPMODEL in land surface models.The 2°×2°grid cell located in mountainous region of Changjiang basin and the other located in relatively flat region of Amazon basin are selected.The topographic indexes are calculated and statistical properties of topographic indexes for two grid cells are extracted using the data from digital elevation model of the Shuttle Radar Topography Mission.River basins and drainage network are extracted using the same dataset and statistics are extracted for each basin.The difference between the cumulative distribution functions and means of topographic index for whole grid cell and for individual basin are analyzed.the cumulative distribution functions for whole grid cell and individual basin are fitted by exponential function.The main conclusions are summarized as follows:(1)Although there are differences between the cumulative distribution functions and means for whole grid cell and individual basin but the differences are not significant.It may be a reasonable simplification to apply TOPMODEL directly to grid cell of GCM;(2)The exponential function can fit the cumulative distribution functions well.These results provide helpful information for designing a TOPMODEL based and simplified hydrological model for use in land surface model.