Insights into rainfall undercatch in differing gauge types and heights: the impact of wind speed and rainfall event intensity

The accurate measurement of rainfall is vital for many aspects of hydrology, including the accurate estimation of water resources. However, the standard installation of raingauges with rims above the ground surface results in a difference between this catch and the amount of rainfall reaching ground level, termed undercatch. Wind disturbance, gauge shape and type of rainfall events have all been shown to impact on rainfall undercatch. The UK standard installation of both storage and tipping bucket raingauges has their rim cited at 30cm above the ground, however the use of weighing gauges, installed at a minimum of 1m above the ground surface, has increased in recent years. The installation of these raingauges raises complex questions of homogeneity of rainfall series given the simultaneous change to both the measurement technique and gauge height. The Centre for Ecology & Hydrology’s meteorological station at Wallingford (Oxfordshire) has historically operated parallel daily storage and tipping-bucket gauges installed at standard height and at ground level in pits. In April 2015, three weighing raingauges were installed at ground level, partial (30cm) and full (1m) heights above the ground. Results from the first three years of the raingauge trials will be presented, looking at the difference in catch between gauge height and instrument types and investigations into the relationship between rainfall catch, wind speed and rainfall event intensity.