Correcting precipitation measurements of TRwS204 in the Qilian Mountains, China

Abstract. With the development and popularization of automatic weather stations, testing the performance of the recording precipitation gauges and deriving the adjustment algorithm have become the top priority. This study mainly analyzed the losses of TRwS_SA (TRwS204 shielded with a single Alter) through correlation and regression methods, and derived the correction algorithm from August 2014 to August 2016 in the Qilian Mountains, China. Results show that precipitation collected with TRwS_SA was 116.2, 5.8, and 7.6 mm less than the true precipitation during the experiment for rain, sleet, and snow, respectively. For the losses, specific errors account for a larger proportion than systematic errors for rainfall and snowfall events, while systematic errors account for a larger proportion than specific errors for sleet events. Regression analyses show that the amount of precipitation and mean air temperature can affect specific errors, particularly for snowfall events. On average, the specific errors per event were 0.6, 0.0, and 0.4 mm for rain, sleet, and snow, respectively, and the systematic errors per event were 0.1, 0.1 and 0.0 mm for rain, sleet, and snow, respectively. For systematic errors, wind speed was still the most significant factor for the catch ratio (CR) of rain and sleet, whereas humidity affected the CR of snow to a certain extent. Currently, given that the transfer functions were agreed to derive from the DFAR (DFIR fence + automatic weighing gauge + shield + precipitation detector), considerable attention should be focused on the specific errors of the automatic weighing gauge.