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Full catalog/TRMM_2A21
TRMM_2A21·v7·dataset

How strongly the ground reflects rain radar (TRMM)

TRMM Precipitation Radar Surface Cross-Section L2 1.5 hours V7 (TRMM_2A21) at GES DISC
land NASA GES_DISC Level 2
In plain English

What it measures. Measures how strongly the Earth's surface reflects the satellite's rain radar (the surface cross-section), and uses that to estimate how much the rain weakened the radar signal along its path, sorting scenes into land/ocean and rain/no-rain.

How it's made. Produced from the Precipitation Radar on the TRMM satellite by feeding its radar power readings into the 'sigma zero' algorithm that uses the surface as a reference.

How & where you'd use it. A specialized input mainly for rainfall scientists; it helps correct radar rain estimates, and a newer GPM-format version (GPM_2APR) is now recommended.

What's measured

SPECTRAL/ENGINEERING › RADAR › SIGMA NAUGHTATMOSPHERE › PRECIPITATION › LIQUID PRECIPITATION › RAIN

Coverage & cadence

  • Time span1997-12-31 → 2014-10-07
  • Measured byTRMM (PR)
  • Processing levelLevel 2
  • Spatial extent-180, -38, 180, 38
  • StatusCOMPLETE

What you can do with it

  • Track deforestation, fire scars and land-cover change
  • Monitor crop and vegetation health (NDVI/EVI)
  • Map how built-up vs. green an area is over time
Official description

The new version of these data is in GPM-like format (consistent with the GPM Dual-frequency Radar data format), and can be found under the name GPM_2APR. This is the sigma zero algorithm, which inputs the PR power (1B21) and computes estimates of the path attenuation and its reliability by using the surface as a reference target. It also computes the spatial and temporal statistics of the surface scattering cross section and classifies the cross sections into land/ocean and rain/no rain categories. Changes in horizontal resolution resulting from the TRMM boost that occurred on 24 August 2001: Pre-Boost (before 7 August 2001): Temporal Resolution: 91.5 min/orbit ~ 16 orbits/day; Swath Width: 215 km; Horizontal Resolution: 4.3 km Post-Boost (after 24 August 2001): Temporal Resolution: 92.5 min/orbit ~ 16 orbits/day; Swath Width: 247 km; Horizontal Resolution: 5.0 km

Get the data

trmm_2a21_access.py
import earthaccess
earthaccess.login(strategy="netrc")          # free Earthdata Login

results = earthaccess.search_data(
    short_name="TRMM_2A21",
    version="7",
    bounding_box=(-122.5, 37.2, -121.8, 37.9),  # your area (W,S,E,N)
    temporal=("2024-01-01", "2024-12-31"),       # your dates
)
files = earthaccess.open(results)   # stream straight from GES_DISC
Browsing CMR needs no login. Downloading or streaming bytes needs a free Earthdata Login + the earthaccess package.