GPM / DPR Level-2 Algorithm Theoretical Basis Document (ATBD)

Date Last Updated
Toshio Iguchi
Shinta Seto
Robert Meneghini
Naofumi Yoshida
Jun Awaka
Minda Le
V. Chandrasekar
Stacy Brodzik
Takuji Kubota
Document Description

This document describes the basic idea of DPR data processing. It was originally written for the
algorithm used in the at-launch version (V03). The algorithm has been modi ed and improved
since then. Although the basic idea of data processing remains the same, the actual ow of
processing, in particular that in the solver module, has changed substantially. As a result, some
part of description in section 3.1 may not be relevant any more.

Changes in the DPR algorithm from V05 to V06

  • A new SRT code has been modi ed to include calculations of Hitschfeld-Bordan PIA as well as a hybrid PIA that combines HB and SRT results. As a result of applying the new PIA in SLV module, erroneously large estimates of high precipitation over ocean (near coast) are mitigated and both DPR(MS) and Ku rain estimates in V06A agree better with Gound Validation data over USA.
  • A new classi cation algorithm is introduced by the University of Washington (Stacy Brodzik and Robert Houze) to reclassify the stratiform rain type. The new algorithm improved an angle-bin dependence of rain classi cation and SLH pro les.

Minor changes in DPR L2 algorithm:

  • KaHS's sidelobe clutter is mitigated and it is used to re-calculated the data base for KuPR's sidelobe clutter.
  • New variables are introduced. They are flagScanPatten in PRE module, PIAhb, PIAhy-brid, reliabFactorHY, reliabFlagHY, stddevEff, stddevHY and zeta in SRT module.
  • The meanings of these variables should be referred to the user's manual.
  • The surface snow index is modi ed for the winter temperature inversions.
  • The latest SRT data base is applied.
  • A bug in agEcho is xed in dual frequency data processing.
  • There are cases of instantaneous retrieved precipitation rate classi ed as stratiform rain that exceed 40 mm/hr. These cases are rare, and the frequency is latitude dependent with more cases near the equator than in the extra-tropics.


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