Reducing systematic errors in rainfall measurements using a new type of gauge

The systematic errors due to aerodynamic effects and wetting losses are known to bias point measurements of precipitation. In the NOPEX project a rain gauge with a new type of wind shield and a special weighing construction is used to minimise these errors. The wind shield consists of a flange surrounding the gauge at the level of the orifice. The idea was to screen the area above the orifice from the disturbance of the wind field by the gauge. At different locations the measured precipitation amounts were compared with the amounts caught by standard gauges. The analysis showed that the catch of the new gauge was higher than that of the standard gauges. A difference of about 3% was related to reduced wind-induced losses, while a difference of about 0.25 mm per event was explained as elimination of wetting loss. At one location the differences were related to wind speed and rainfall intensity to evaluate the effect of the wind shield. The relative differences were largest (20%) for events with low intensity and high wind speed. (C) 1999 Elsevier Science B.V. All rights reserved.