Performance of rain gauges in a field study at the Hong Kong International Airport

A number of rain gauges are set up at the meteorological garden of the Hong Kong International Airport (HKIA) during the summer of 2010 to study their performance. They include drop counting rain gauges (with and without the application of drop size correction), a 0.5-mm tipping bucket rain gauge, and a weighing rain gauge. The drop size correction is made for the drop-counting rain gauge based on dynamic calibration of the gauge. Their performance is studied using the daily rainfall obtained by manual measurement of the rainfall amount. The heavy rain episodes include summer monsoonal rain in association with troughs of low pressure and active southwesterlies as well as tropical cyclones. Based on the limited number of heavy rain events in the study period, it appears that drop-counting rain gauge without the application of drop size correction shows the best performance. On the other hand, the application of correction for drop-counting rain gauge appears to show a tendency to over-estimate the rainfall amount at times. The implications of the study results in the selection of an operational rain gauge for synoptic weather observation would be discussed.