A comparison of rainfall measurements from multiple instruments

[摘要] Simultaneous observations of rainfall collected by a tipping bucket raingauge (TBRG), a weighing rain gauge (WRG), an optical rain gauge(ORG), a present weather detector (PWD), a Joss–Waldvogel disdrometer (JWD),and a 2-D video disdrometer (2DVD) during January to October 2012 wereanalyzed to evaluate how accurately they measure rainfall and drop sizedistributions (DSDs). For the long-term observations, there were differentdiscrepancies in rain amounts from six instruments on the order of 0% to27.7%. The TBRG, WRG, and ORG have a good agreement, while the PWD and2DVD record higher and the JWD lower rain rates whenR > 20 mm h⁻¹, the ORG agrees well with JWD and 2DVD,while the TBRG records higher and the WRG lower rain rates whenR > 20 mm h⁻¹. Compared with the TBRG and WRG,optical and impact instruments can measure the rain rate accurately in thelight rain. The overall DSDs of JWD and 2DVD agree well with each other,except for the small raindrops (D < 1 mm). JWD can measuremore moderate-size raindrops (0.3 mm < D < 1.5 mm)than 2DVD, but 2DVD can measure more small-size raindrops(D < 0.3 mm). 2DVD has a larger measurement range; moreoverall raindrops can be measured by 2DVD than by JWD in different rain rateregimes. But small raindrops might be underestimated by 2DVD whenR > 15 mm h⁻¹. The small raindrops tend to be omittedin the more large-size raindrops due to the shadow effect of light. Therefore, themeasurement accuracy of small raindrops in the heavy rainfall from 2DVD shouldbe handled carefully.

[学科分类] 几何与拓扑