Estimation of Wind Induced Catchment Errors for the PACRAIN Database

Corrections for wind induced catchment errors have been derived for rainfall records contained in the PACRAIN database. Simulated wind flows around rain gauges were used to compute rain drop trajectory displacements over gauges’ horizontal neighborhoods and determine drop collection statuses. The process was repeated over representative drop size distributions and observed wind conditions to estimate gauge catchment efficiencies relative to rain rates in unperturbed flow. Corrections were first obtained for high resolution TAO syphon gauge data, provided courtesy of the Global Tropical Moored Buoy Array (GTMBA) Project Office of NOAA / Pacific Marine Environmental Laboratory (PMEL), due to the availability of collocated anemometry. The procedure was extended to other observations in the PACRAIN database where gauge type is known, using local winds where available and GDAS reanalysis wind estimates elsewhere. Spatial cross estimation was employed to explore sensitivities to drop size distribution and wind averaging.