Bias correction of precipitation data and its effects on aridity and drought assessment in China over 1961-2015.

The accuracy of gauge-measured precipitation (P) affects drought assessment since drought severity changes due to precipitation bias correction. This research investigates how drought severity changes as the result of bias-corrected precipitation (P) using the Erinc's index I and standardized precipitation evapotranspiration index (SPEI). Daily and monthly P values at 552 sites in China were determined using daily P and wind speed and air temperature data over 1961-2015. P-based I values were generally larger than P-based I for most sub-regions in China. The increased P and P-based I values indicated wetter climate conditions than previously reported for China. After precipitation bias-correction, Climate types changed, e.g., 20 sites from severe-arid to arid, and 11 sites from arid to semi-arid. However, the changes in SPEI were not that obvious due to precipitation bias correction because the standardized index SPEI removed the effects of mean precipitation values. In conclusion, precipitation bias in different sub-regions of China changed the spatial and temporal characteristics of drought assessment.