Spatial Interpolation Methods of Daily Precipitation

High-resolution precipitation field is very useful in the study of precipitation-induced geological hazards. The quality of the precipitation field varies if different interpolation methods are used. In this study inverse distance weighting and ordinary Kriging methods are applied to interpolate daily precipitation of stations over 26°—34°N, 103°—115°E into 1 km×1 km grid.The interpolation results are then compared to indicate which method better represents the spatial pattern and intensity of precipitation. Results show that the two methods perform similarly well by their correlation coefficients of 0.83 and 0.82 between observed and interpolated precipitation in the cross validation test. When daily precipitation is equal to or greater than 10 mm, both methods are less efficient and the correlation is down to 0.66 and 0.67. The correlation coefficient, as an indicator of the interpolation quality, has a clear seasonal trend with a maximum in spring and a minimum in summer. From analysis to the accuracy of interpolation for heavier precipitation, both methods show unsatisfied results and Inverse distance weighting method with more error rate. The accuracy decrease from 80% for precipitation exceeding 10 mm to 65% for precipitation exceeding 25 mm, particular in rainstorm with above 50 mm precipitation, the accuracy is only 50%. The observed precipitation is systematically underestimated by both methods and the interpolation quality gradually decreases for heavy precipitation. Generally, ordinary Kriging is better than inverse distance weighting. But the running time is a disadvantage when the ordinary Kriging method is applied into operational system, inverse distance weighting method may be substituted for it.