Precipitation Gauge Collection Efficiency with Wind Speed and Hydrometeor Characteristics

Automated catchment-type precipitation gauge measurements are critical for weather, climate, hydrology, transportation, and validation of remote sensing products. The systematic bias and uncertainty of these catchment gauges due to wind-induced undercatch is a major challenge, particularly with respect to the measurement of solid precipitation. Transfer functions developed through the World Meteorological Organization Solid Precipitation Intercomparison Experiment (WMO-SPICE) have demonstrated reductions in the systematic bias of solid precipitation measurements; however, large variability in measured values relative to reference Double Fence Automated Reference (DFAR) measurements persists. Comparisons of replicate weighing gauge and shield configurations exhibit reduced measurement variability, suggesting the potential for further improvements in adjustment functions. One avenue for improvement is the ability of transfer functions to distinguish among different precipitation types and their aerodynamic properties. In this study, Environment Canada’s Precipitation Occurrence Sensor System (POSS), which is an upward pointing mini Doppler Radar, is used to characterize precipitation. Measurements were conducted at the Centre for Atmospheric Research Experiments (CARE) test site in Egbert, Ontario, during WMO-SPICE. New transfer functions are developed that incorporate the effects of both wind speed and precipitation characteristics on the catch efficiency of automated precipitation gauges. The application of these functions results in significant improvements in the accuracy of adjusted precipitation accumulation values relative to other transfer functions. These results suggest that incorporating measurements of precipitation characteristics into field configurations can provide high-accuracy precipitation accumulation estimates where the deployment of a DFAR is not practical.