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

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-Altershielded TRwS204 automatic weighing gauge(TRwS_(SA)) relative to the adjusted manual measurements(reference precipitation) from the Chinese standard precipitation gauge in a doublefence wind shield(CSPG_(DF)) in the Hulu watershed in the Qilian Mountains, China. The measurements were compared over the period from August 2014 to July2017, and the transfer function derived from the work by Kochendorfer et al.(2017 a) for correcting windinduced 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.

Which adjustment methods are suitable for the wind-induced errors of Geonor T-200BM3 precipitation weighing gauges in a periglacial site?

Single Alter shielded T-200BM3 weighing precipitation gauges are widely used in the measurement of all precipitation types(rainfall,snow and mixed precipitation)in unattended boreal or alpine regions,but their original datasets must be adjusted for undercatch errors caused by wind in snowy,windy and harsh environments.Therefore,previous researchers have developed many adjustment methods for all precipitation types on different time scales.However,which adjustment method is suitable for T-200BM3 weighing gauge wind-induced error adjustment in harsh alpine regions is unclear.Therefore,precipitation measurement intercomparison experiments were conducted in the Qilian Mountains from July 2018 to July 2021,and eight adjustment methods;were evaluated for wind-induced errors for daily,individual precipitation event,hourly,and half-hourly time scales.Z2004 outperformed the other adjustment methods in regard to the daily measurements of snow and mixed precipitation.Regarding individual snowfall events,M2007 reduced the absolute value of RMSE(bias)from 1.44 to 1.32 mm(0.77-0.24 mm)and could be recommended for snowfall event adjustment.K2017-1 attained a better performance than K2017-2 in regard to half-hourly snowfall and mixed sample adjustment and was more suitable for half-hourly snowfall sample adjustment.K2017-1 reduced the absolute value of bias from 0.07 to 0.00 mm for snowfall.Finally,Z2004,M2007,and K2017-1 yielded better adjustment results for the daily accumulation precipitation amount(>2 mm d−1),individual snowfall events(>2 mm per event),and half-hourly accumulation snowfall or mixed samples(>1 mm 30 min−1),respectively.However,further intercomparison in different climate regions is needed for trace precipitation samples.

Intercomparison measurements from commonly used precipitation gauges in the Qilian Mountains

Precipitation data is vital fundamental data for climate change.However,obtaining precise gauge-measured precipitation in high-altitude mountains is challenging,and the precipitation obtained from various gauge types at the same station may vary.To understand the differences in precipitation observations among the three commonly used gauges in China(Chinese Standard Precipitation Gauges(CSPG),Total Rain weighing Sensor(TRwS),and Geonor T-200B(T200B))in high-altitude mountains and to recommend a stable and cost-effective weighing gauge,a precipitation intercomparison experiment was conducted at Hulu-1 station in the Qilian Mountains.The wind-induced error in measurement was corrected with the‘universal’transfer function recommended by the Word Meteorological Organization.The comparison results,adjusted for systematic errors,showed that the rain,snow and mixed precipitation of CSPG and TRwS equipped with the same octagonal vertical double fence shields(CSPGDF and TRwSDF)and single-Alter shields(CSPG_(s)and TRwSs)were close,while the precipitation of Tretyakov-shielded T200B was notably higher than that of CSPG_(s)and TRwSs.The average differences in annual and daily precipitation between CSPGDF and TRwSDF from 2017 to 2021 were 12.9 mm and 0.10 mm,respectively.The daily precipitation difference between CSPG_(s)and TRwSs from April 2019–December 2021 was 0.10 mm,while the differences between T200Bs and CSPG_(s)and TRwSs was 0.28 mm and 0.38 mm,respectively.The wind shield performance of Alter and Tretyakov was not much different at Hulu-1 site with low wind speed,thus the measurement principle of T200Bs was the primary cause of the high observations.Taking the corrected CSPGDF measurement as the standard,the dynamic loss of CSPG_(s)was 17.6%,while that of CSPGUn was 55.6%,indicating that the single-Alter shield could effectively reduce the impact of wind on precipitation measurement.Considering the comparison results and the price difference of the instruments,it was recommended to use a single-Alter shielded TRwS gauge for precipitation observation in high-altitude mountains.