COMPARISON OF GEOSTATISTICAL METHODS FOR ESTIMATING THE AREAL AVERAGECLIMATOLOGICAL RAINFALL MEAN USING DATA ON PRECIPITATION AND TOPOGRAPHY

The results of estimating the areal average climatological rainfall me an in the Guadalhorce river basin in southern Spain are presented in t his paper. The classical Thiessen method and three different geostatis tical approaches (ordinary kriging, cokriging and kriging with an exte rnal drift) have been used as estimators and their results are compare d and discussed. The first two methods use only rainfall information, while cokriging and kriging with;In external drift use both precipitat ion data and orographic information (easily accessible from topographi c maps). In the case study presented, kriging with an external drift s eems to give the most coherent results in accordance with cross-valida tion statistics. If there is a correlation between climatological rain fall mean and altitude, it seems logical that the inclusion of topogra phic information should improve the estimates. Kriging with an externa l drift has the advantage of requiring a less demanding variogram anal ysis than cokriging. (C) 1998 Royal Meteorological Society.