Precipitation measurement biases in an arid setting of central Asia: using different methods to divide precipitation types

摘要

Accurate precipitation data play important roles in climate and hydrology research at regional and global scales. The correction of system errors associated with precipitation represents a feasible and effective way to improve the accuracy of rainfall data. We analysed and corrected rainfall data collected at 45 meteorological sites in Xinjiang over 55 years (from 1 January 1960 to 31 December 2014) in terms of the wetting loss, trace precipitation and wind-induced loss, with 2 judgement methods of precipitation types. We based our analysis on daily temperature, wind speed, precipitation, relative humidity and air pressure data. Precipitation after correction was compared to precipitation before correction. The primary conclusions are: (1) Based on the new method of distinguishing precipitation types, the results show more snow days, fewer mixed precipitation days and slightly fewer rain days than the traditional method. (2) The sum values of corrections for each loss based on the new method of distinguishing precipitation types are higher than those based on the traditional method in spring and autumn. The sum values of corrections and differences of each loss are all larger in North Xinjiang and smaller in South Xinjiang. The sum values of total corrections are larger on the north slope of the Tianshan Mountains and smaller on the south slope, and they decrease from the south slope to South Xinjiang. (3) The median values of the sum of each loss and total correction in the northern region of Xinjiang are higher than those in the central region of Xinjiang, which are higher than those in the southern region of Xinjiang on the whole. (4) Precipitation increases after correction. The annual mean corrected values at Bayanbulak (in the Tianshan Mountains), Altay (in North Xinjiang) and Yutian (in South Xinjiang) are 81.48, 54.60 and 12.55 mm, respectively.