黄土高原降水计算插值与插值计算结果的对比分析

收集黄土高原及周边地区74个气象站1952—2001年降水数据,用ArcGIS9.3普通克里金（ordinary kriging）插值法采用计算插值（calculate then interpolate,CI）和插值计算（interpolate then calculate,IC）的方法生成黄土高原地区1952—2001年50 a平均年降水量和年降水量线性趋势系数空间分布表面,并对其进行统计分析和地形分析。结果表明：1）从插值结果统计值看,CII、C法生成的黄土高原地区50 a平均年降水量和线性趋势系数空间分布表面平均值分别为421.65、421.56 mm和-0.541 0、-0.423 1 mm/a,相似系数分别为99.78%和95.99%,二者一致性良好;2）从插值结果表面光滑度看,IC法稍优于CI法,借用地形分析对生成表面进行坡度、坡向运算,可作为评价表面光滑度、空间数量变化特征和空间方向变化特征的直观方法;3）黄土高原地区50 a平均年降水量具有东南多西北少、南多北少、东多西少的分布规律,其中服从东南西北、南北和东西方向递减的地带性分布规律区域占黄土高原地区面积的89.34%,非地带性分布规律区域占10.66%;4）CI和IC法计算的黄土高原地区1952—2001年降水线性趋势系数平均-0.541 0和-0.423 1 mm/a,黄土高原地区年降水量有明显减少趋势。

Comparison and analysis of precipitation surfaces produced by CI and IC two approaches in Loess Plateau

Collecting precipitation at 74 stations in/around Loess Plateau Region from 1952 to 2001,surfaces of annual average precipitation and linear trend of Loess Plateau from 1952 to 2001 were interpolated with ARCGIS 9.3 using Geostatistical Analyst adopting "calculate then interpolate"(CI) and "interpolate then calculate"(IC) approach.The Result showed that: 1) Total annual average precipitation of Loess Plateau from 1952 to 2001 and its linear trend coefficient were 421.65 mm,421.56 mm and-0.462 1 mm/a,-0.423 1 mm/a respectively.Similarity coefficients of them were 99.78% and 95.99%,which showed a good accordance between them.2) Surfaces produced by IC approach were a little smoother than that by CI approach.Terrain analysis methodology was a visualizing method of evaluating the precision,smoothness,the spatial amount change and direction change of precipitation surface and linear trend surface.3) Area of decreasing direction of spatial trend of precipitation was mainly from Southeast to Northwest,then South to North,Southwest to Northeast and East to West where is up to 89.34% of Loess Plateau,which can be regarded as zonality distribution law.The others which belonged to non-zonality distribution law are 10.66%.4) Precipitation of Loess Plateau from 1952 to 2001 has a significant decreasing trend with an average linear trend coefficient of-0.541 0 mm/a by CI approach or-0.423 1 mm/a by IC approach.