Estimating Summer Precipitation Over the Tibetan Plateau With Geostatistics and Remote Sensing

Although precipitation is important to climatology, hydrology, and agricultural research, the spatial pattern of precipitation over the Tibetan Plateau is difficult to determine because of complex surface conditions and a sparse rain gauge network. In the present article, a method we named FETCH_OCK-based on a combination of Yin et al's Fetch method (2008) and ordinary cokriging (OCK)-is proposed; it was used to estimate monthly summer precipitation over the Tibetan Plateau, which has limited rain gauge observations and a restricted satellite precipitation dataset. First, the monthly ground observations measured by rain gauges were interpolated using OCK, with a digital elevation model (DEM) as the covariant. Second, the spatial variability of the precipitation monitored by satellite was extracted from the Climate Prediction Center morphing (CMORPH) satellite precipitation dataset by calculating a parameter (FETCH) developed from Yin et al's Fetch parameter. Finally, the precipitation datasets estimated by OCK were corrected by the FETCH parameter derived from the CMORPH satellite precipitation dataset. Summer (June to August) precipitation over the Tibetan Plateau from 2005 to 2009 was estimated using this model. The precipitation datasets estimated by FETCH_OCK were tested using ground observations from 55 independent rain gauges. The results indicate that the FETCH_OCK model not only is an improvement compared with the input precipitation datasets (OCK and CMORPH) but also performs better than other widely used precipitation datasets, including universal kriging with DEM as a covariant and Tropical Rainfall Measuring Mission 3B43. The present study aims to correct the smoothing effect of kriging interpolation models and to provide a more accurate precipitation dataset for the Tibetan Plateau.