Analysis and Correction of Errors in PrecipitationMeasurement at the Head of UrumqiRiver,Tianshan
Yang Daqing, Jiang Tong, Zhang Yinsheng and Kang Ersi (Lanzhou Institute of Glaciology & Geocryology, Chinese Academy of Sciences)
The concepts of wind effect, wetting and evaporation losses in precipitation measurement are introduced and the factors affecting the losses are analysed. Based on the comparative measuements of precipitation with different gauges and wind shields and also on the observation of wetting and evaporation losses at the head of the Urumqi River in the summer of 1986, the 26% cacth deficie ncy (13.9% for wind effect, 8.4% for wetting and 3.7% for evaporation respectively) for a standard gauge of China is determined. With the correction of the errors mentioned above ,the accurate value of average annual precipitation ,524.2 mm and 645.8 mm, is obtained respectively at the altitudes of 3540 m a.s.l and 4050 m a.s.l at the head of the Urumqi River.