Precipitation adjustment by the OTT Parsivel² in the central Qinghai–Tibet Plateau

AbstractGround observation of precipitation is fundamental in preparing and evaluating various precipitation datasets, which are essential for running hydrologic and climatologic models. The undercatch of traditional precipitation gauges leads to significant uncertainty in ground observation, which is particularly severe in the central Qinghai–Tibet Plateau (QTP). To evaluate the undercatch biases, intercomparison experiments between Geonor T‐200B, the Chinese standard precipitation gauge (CSPG), and OTT Parsivel2 disdrometer were conducted at Tanggula (TGL) and Wudaoliang (WDL) sites. The adjustment schemes for 30‐min and daily precipitation were proposed and applied to 30‐min precipitation at TGL over 10 years and the monthly precipitation of the national meteorological stations on the QTP over 37 years. The results indicated that after adjustment the annual precipitation increased by 49.09% at TGL and 16.41% over the QTP. Snow took up 9.91% of the annual precipitation over the QTP, while it took up over 60% at TGL. Because of the high snow proportion, the central QTP had lower catch ratio and higher adjustment ratio than the QTP average. From 1981 to 2017, the central QTP presented a wetter trend, and the annual precipitation increased by 3.15 mm/yr, higher than the QTP average. Moreover, in the central QTP, precipitation increased more in wet than dry seasons, which were 2.45 and 0.83 mm/yr, respectively. While on the entire QTP, the dry season precipitation increased slightly more than the wet season, which were 0.67 and 0.50 mm/yr, respectively. On the QTP, adjustment amount presented an increasing trend from the northwest to the southeast, whereas annual adjustment ratio was the opposite. This study could enhance the knowledge of precipitation characteristics over the QTP, especially in the central region. More effort will be given to the calibration and uncertainty evaluation of the proposed schemes in future work.