Evaluation and comparison of three long-term gauge-based precipitation products for drought monitoring over mainland China from 1961 to 2016

Three newly released, gauge-based precipitation products (GPPs), i.e., the Global Precipitation Climatology Center full data monthly version 2018 (GPCC 8.0), the Climate Research Unit Time Series version 4.03 (CRU TS 4.03), and the Center for Climatic Research-University of Delaware Terrestrial Precipitation: 1900-2017 Gridded Monthly Time Series version 5.01 (UDel 5.01), were evaluated and compared with the China Gauge-based Daily Precipitation Analysis (CGDPA) dataset. The evaluations involved drought monitoring over mainland China by using the Standardized Precipitation Index (SPI). The results indicated that the GPPs performed well in capturing precipitation spatial patterns (correlation coefficients > 0.9) and interannual variations (correlation coefficients > 0.7) for most regions, with the exceptions of the Xinjiang and Qinghai-Tibet plateau (TP) regions. It was also noted that the accuracy of SPIs calculated using GPPs (SPIg) showed no apparent variations at various timescales, and a 3-month SPI metric was selected for further analyzing. When examining the spatiotemporal accuracies of SPIg, we found that they exhibited high levels of consistency, small errors, and high degrees of detectivity in Eastern China, and comparatively high spatial heterogeneity in Western China, particularly in the TP region. The regional mean SPIg performances improved at the time series, as their individual spatial heterogeneities were offset by averaging. The GPPs were able to satisfactorily capture the characteristics of typical drought events, such as drought area, centroids, and severity, for the four selected specific regions. Overall, the long-term GPP records showed great potential in quantifying drought over mainland China, especially in Eastern China and Southwest. Among the three GPPs, it was found that GPCC 8.0 performed the best, in both precipitation estimation and drought monitoring, while no distinct distinctions were apparent between the CRU TS 4.03 and UDel 5.01 products. These results showed that the long-term GPPs could be applied to large-scale drought monitoring, and the findings could provide useful references for selecting gauge-based precipitation data for various hydrometeorological applications.