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DAAC-TRMM-3A25 data
This dataset is created from the TRMM products 3A25 in the GSFC Earth Sciences (GES) Distributed Active Archive Center (DAAC), NASA.
The primary objective of algorithm 3A25 is to compute various rainfall statistics over a month from the level 2 PR products. The statistics are derived at two spatial resolutions: (1) a standard space scale of 5 degrees by 5 degrees (latitude x longitude) cells and (2) a high resolution subset of 0.5 degree x 0.5 degree cells. The output variables include rainfall rate (mm h-1) profile at 2, 4, 6, 10, and 15 km, fractional rain, snow ice layer, and surface rain rate (mm h-1). The output statistics include probabilities of occurrence, means and standard deviations, histograms, and correlation coefficients.
All statistics in 3A25, except near-surface rain rate, are computed only when rain is judged in 1C21 to be ""certain."" When rain is judged in 1C21 to be ""possible,"" the observation is treated as a ""no-rain"" observation. For the near-surface rain rate, the statistics (mean, standard deviation, and histogram) are computed for ""rain-possible"" as for the usual ""rain-certain."" Because the ""rain-possible"" cases are dominated by noise so that the probability of false-alarm is high, the ""rain-certain"" statistics should be considered as more representative of the TRMM radar data.
Three types of rain rates are defined in 3A25: (1) a ""near-surface"" rain rate that is obtained from the range bin closest to the surface which is not corrupted by the surface clutter; (2) a path-averaged rain rate calculated by summing the values from the storm top (first gate where rain is detected) to the last gate (gate nearest to the surface uncontaminated by surface clutter) and dividing by the number of gates in the interval; and (3) those at fixed heights above the ellipsoid (2, 4, 6, 10, and 15 km).
The data served in IPRC only includes five variables with 0.5*0.5 grid.
| Variables | non-zero rain rates (mm/hpur),Convective Rain Rate (mm/hour), Stratiform Rain Rate (mm/hour), non-zero near-surface rain rate(mm/hour), non-zero near-surface rain rate(mm/hour) |
| Zonal | Global by 0.5 deg |
| Meridional | 36.75S to 36.75N by 0.5 deg |
| Vertical | surface and 4 Levels: path average, 2.0Km, 4.0Km and 6.0Km
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| Temporal | Dec 1997 to Apr 2007 by 1 month(s) |
| Static? | no |
| Volume | 405.8MB |
| Server | DODS & LAS; public |
| Source | http://disc.sci.gsfc.nasa.gov/precipitation/TRMM_README/TRMM_3A25_readme.shtml |
| Acquired | Jul 17, 2003 (updated June 2007) |
| APDRC contact | Yongsheng Zhang |
| Supplements | readme.f |
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