Comparison of Global Precipitation Estimates across a Range of Temporal and Spatial Scales

Characteristics of precipitation estimates for rate and amount from three global HRPPs, four global Climate Data Records, and four reanalyses are compared here. Estimates of global precipitation differ widely from one product to the next, with some differences likely due to differing goals in producing the estimates. High-resolution precipitation products (HRPPs) are intended to produce the best instantaneous precipitation estimate. Climate data records of precipitation emphasize homogeneity over instantaneous accuracy. Precipitation estimates from global reanalyses are dynamically consistent with the large scale circulation but tend to compare poorly to rain gauge estimates as they are forecast by the reanalysis system and precipitation is not assimilated. Patterns of means are consistent. As expected, variance is highest where means are large, and the same is true for the average spread among data sets. Regionally, differences in the means and variances are as large as the means and variances respectively. Temporal correlation, rain rate and rain amount distributions, and biases in time evolution are explored using temporal and spatial averaging. It is shown that differences on annual time scales and continental regions are around 0.8mm/d, which corresponds to 23W/m². These wide variations in the estimates, even for global averages, highlight the need for better constrained precipitation products in the future.