Global precipitation at one-degree daily resolution from multisatellite observations

The One-Degree Daily (1DD) technique is described Tor producing globally co mplete daily estimates of precipitation on a 1 degrees x 1 degrees lat/long grid from currently available observational data. Where possible (40 degre es N40 degreesS), the Threshold-Matched Precipitation Index (TMPI) provides precipitation estimates in which the 3-hourly infrared brightness temperat ures (IR T-b) are compared with a threshold and all "cold" pixels are given a single precipitation rate. This approach is an adaptation of the Geoatat ionary Operational Environmental Satellite Precipitation Index, but for the TMPI the IR T-b threshold and conditional min rate are set locally by mont h from Special Sensor Microwave Imager-based precipitation frequency and th e Global Precipitation Climatology Project (GPCP) satellite-gauge (SG) comb ined monthly precipitation estimate, respectively. At higher latitudes the 1DD features a rescaled daily Television and Infrared Observation Satellite Operational Vertical Sounder (TOVS) precipitation. The frequency of rain d ays in the TOVS is scaled down to match that in the TMPI at the data bounda ries, and the resulting nonzero TOVS values are scaled locally to sum to th e SC; (which is a globally complete monthly product). The GPCP has approved the IDD as an official product, and data have been pr oduced for 1997 through 1999, with production continuing a few months behin d real time (to allow access to monthly input data). The time series of the daily IDD global images shows good continuity in time and across the data boundaries. Various examples are shown to illustrate uses. Validation for i ndividual gridbox values shows a very high mean absolute error, but it impr oves quickly when users perform time/space averaging according to their own requirements.