South African Weather Service operational satellite based precipitation estimation technique: applications and improvements

摘要

Extreme weather related to heavy or more frequent precipitation events seemto be a likely possibility for the future of our planet. While precipitationmeasurements can be done by means of rain gauges, the obvious disadvantagesof point measurements are driving meteorologists towards remotely sensedprecipitation methods. In South Africa more sophisticated and expensivenowcasting technology such as radar and lightning networks are available,supported by a fairly dense rain gauge network of about 1500 daily gauges.In the rest of southern Africa rainfall measurements are more difficult toobtain. The local version of the Unified Model and the Meteosat SecondGeneration satellite data are ideal components of precipitation estimationin data sparse regions such as Africa. In South Africa hourly accumulationsof the Hydroestimator (originally from NOAA/NESDIS) are currently used as asatellite based precipitation estimator for the South African Flash FloodGuidance system, especially in regions which are not covered by radar. Inthis study the Hydroestimator and the stratiform rainfall field from theUnified Model are both bias corrected and then combined into a newprecipitation field. The new product was tested over a two year period andprovides a more accurate and comprehensive input to the Flash Flood Guidancesystems in the data sparse southern Africa. Future work will includeupdating the period over which bias corrections were calculated.