Adjusting precipitation measurements from the TRwS204 automatic weighing gauge in the Qilian Mountains, China

Abstract

With the popularity of the automatic precipitation gauges in national weather stations, testing their performance and adjusting their measurements are top priorities. Additionally, because different climatic conditions may have different effects on the performance of the precipitation gauges, it is also necessary to test the gauges in different areas. This study mainly analyzed precipitation measurements from the single-Alter-shielded TRwS204 automatic weighing gauge (TRwS_SA) relative to the adjusted manual measurements (reference precipitation) from the Chinese standard precipitation gauge in a double-fence wind shield (CSPG_DF) in the Hulu watershed in the Qilian Mountains, China. The measurements were compared over the period from August 2014 to July 2017, and the transfer function derived from the work by Kochendorfer et al. (2017a) for correcting wind-induced losses was applied to the TRwS_SA measurements. The results show that the average loss of TRwS_SA measurements relative to the reference precipitation decreased from 0.55 mm (10.7%) to 0.51 mm (9.9%) for rainfall events, from 0.35 mm (8.5%) to 0.22 mm (5.3%) for sleet events, and from 0.49 mm (18.9%) to 0.33 mm (12.7%) for snowfall events after adjustment. The uncorrected large biases of TRwS_SA measurements are considered to be mainly caused by specific errors of TRwS_SA, different gauge orifice area and random errors. These types of errors must be considered when comparing precipitation measurements for different gauge types, especially in the mountains.