Earth Data School
About
Full catalog/TRMM_1C21
TRMM_1C21·v7·dataset

Raw rain-radar echoes over the tropics (TRMM)

TRMM Precipitation Radar Power and Reflectivity L1C 1.5 hours V7 (TRMM_1C21) at GES DISC
land NASA GES_DISC Level 1
In plain English

What it measures. Raw radar echoes from the tropics, showing how strongly rain and other targets reflect the radar signal (reflectivity) in three dimensions, without correcting for signal weakening on the way through rain.

How it's made. Produced from the TRMM Precipitation Radar, the first weather radar in space, by converting the recorded echo power into reflectivity values for every range bin.

How & where you'd use it. A building-block input for measuring the 3-D structure and depth of tropical rainfall; researchers generally use the corrected, higher-level rain products built from it rather than these raw echoes.

What's measured

SPECTRAL/ENGINEERING › RADAR › RADAR BACKSCATTERSPECTRAL/ENGINEERING › RADAR › RADAR REFLECTIVITY

Coverage & cadence

  • Time span1997-12-07 → 2015-04-01
  • Measured byTRMM (PR)
  • Processing levelLevel 1
  • 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 TRMM Precipitation Radar (PR), the first of its kind in space, is an electronically scanning radar, operating at 13.8 GHz that measures the 3-D rainfall distribution over both land and ocean, and defines the layer depth of the precipitation. The 1C21 calculates the effective radar reflectivity factor at 13.8 GHz without any propagation loss (due to rain or any other atmospheric gas) correction (Zm). Therefore, the Zm value can be calculated just by applying a radar equation for volume scatter with PR system parameters. The noise-equivalent Zm is about 21 dBZ. Through the subtraction of the system noise, the Zm value as small as 16 or 18 dBZ are still usable although the data quality is marginal. In 1C21, all echoes stored in 1B21 are converted to "dBZ" unit. This is not relevant for "non-rain" echo; however, this policy is adopted so that the 1B21 and 1C21 product format should be as close as possible except for the following points: - Radar quantity is Zm in dBZ unit instead of received power (dBm). - Data at echo-free range bins judged in 1B21 are replaced with a dummy value. 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_1c21_access.py
import earthaccess
earthaccess.login(strategy="netrc")          # free Earthdata Login

results = earthaccess.search_data(
    short_name="TRMM_1C21",
    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.