Precipitation regridding – Impacts at global scale

Re-gridding considerably alters precipitation statistics. Despite this fact, regridding precipitation datasets is commonly performed for coupling or comparing different models/datasets. In general, several studies have highlighted the effects of regridding at regional scale. In this study, the effects of re-gridding precipitation are emphasized at a global scale using different regridding methods, size of the shifts and resolutions of the dataset. Substantial differences are noted at high quantiles and precipitation dry (or wet-dry frequency) is altered to a great extent. Specifically, a difference of 46 mm in high (0.95) quantiles and a reduction of 30% wet-dry frequency is noted. The differences increase with the size of the grid shift at higher quantiles and vice versa for low quantiles. As the grid resolution increases, the difference between original and regridded data declines, yet the shift size dominates for high quantiles for which the differences are higher. Spatially, large differences at high quantiles in tropical land regions, and at low quantiles in polar regions are noted. These impacts are approximately same for the three different (first order conservative, bilinear, and distance weighted averaging) regridding methods considered in this study. Overall, re-gridding should be performed with caution as it can alter the statistical properties of precipitation to a great extent and adds uncertainty to further analysis of using in any models or in combined precipitation products.