GPCP Rainfall estimate

Daily precipitation estimates from NASA Oct 1996-Sep 2009. (see http://precip.gsfc.nasa.gov/). Converted to netcdf format.

This data set is a companion to the GPCP Version 2.1 SG Combination (which the reader should see for descriptions,including references). Many users need precipitation estimates at finer space and time scales than the Version 2 SG set provides. The 1DD V1.1 is computed by the GPCP Global Merge Development Centre, lead by Dr Robert Adler in the NASA/GSFC Laboratory for Atmospheres. This takes place 2-3 months after the end of the month, once all input data sets become available.

In this first release, the 1DD uses the "best" quasi-global observational estimators of underlying statistics to adjust quasi-global observational datasets that have desirable time/space coverage. Specifically,

1. Special Sensor/Microwave Imager (SSM/I; 0.5°x0.5° by orbit, GPROF algorithm) provides fractional occurrence of precipitation, and
2. GPCP Version 2.1 Satellite-Gauge (SG) combination (2.5°x2.5° monthly) provides monthly accumulation of precipitation to algorithms applied to
3. geosynchronous-orbit IR (geo-IR) Tb histograms (1°x1° grid in the band 40°N-40°S, 3-hourly),
4. low-orbit IR (leo-IR) GOES Precipitation Index (GPI; same time/space grid as geo-IR),
5. TIROS Operational Vertical Sounder (TOVS; 1°x1° on daily nodes, Susskind algorithm), and
6. Atmospheric Infrared Sounder (AIRS; 1°x1° on daily nodes, Susskind algorithm).

It is expected that the 1DD will see extensive development work. This may include: diurnally varying calibrations; extension back in time; additional sensors; direct use of microwave estimates; and refined combination approaches.

The current data set extends from October 1996--present, and continues to be extended from October 1996--present (with some delay to allow input fields to be computed). The primary product in the 1DD dataset is a combined observation-only dataset. That is, a gridded analysis based on satellite estimates of rainfall is constrained by a monthly analysis that is based on gauge and satellite observations. The initial product suite consists of the "final" estimates of precipitation.

Missing values are denoted by the value -99999., and the units are mm/day.