This is the new, GPM-like, format for TRMM Precipitation Radar L2 data that now incorporates what was known as 2A21, 2A23 and 2A25 datasets.

The primary purpose of 2A21 is to compute the path-integrated attenuation (PIA) using the surface reference technique (SRT). The surface reference technique rests on the assumption that the difference between the measurements of the normalized surface cross section outside and within the rain provides an estimate of the PIA. The secondary purpose of 2A21 is to compute the normalized radar cross sections ("sigma-not" or Normalized Radar Cross-Sectin (NRTS)) of the surface under rain-free conditions.

Main objectives of 2A23 are as follows:
(a) Detection of bright band (BB) and determination of the height of BB, the
strength of BB, and the width (i.e. thickness) of BB when BB exists.
(b) Classification of rain type into the following three categories:

• stratiform,
  • convective,
  • other,
    where "other" means (ice) cloud only and/or maybe noise.
    (c) Detection of shallow isolated and shallow non-isolated.
    (d) Output of Rain/No-rain flag.
    (e) Computation of the estimated height of freezing level.
    (f) Output of the height of storm top.

The objectives of 2A25 are to correct for the rain attenuation in measured radar reflectivity (Zm) and to estimate the instantaneous three-dimensional distribution of rain from the TRMM Precipitation Radar (PR) data. The estimated vertical profiles of attenuation-corrected radar reflectivity factor (Ze) and rainfall rate (R) are given at each resolution cell of the PR. The estimated rainfall rate at the actual surface height and the average rainfall rate between the two predefined altitudes (2 and 4 km) are also calculated for each beam position.

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