TABLE 2.1 Differences in the Context for Launch of TRMM Versus the GPM Core Satellite

Context for Launch of TRMM

Context for Launch of the GPM Core Satellite

Experimental sensors on board (the first deployment of quantitative weather radar in space), including multiple sensors on one spacecraft (e.g., precipitation radar and passive microwave imager).

Proven sensor technology; potential for the GPM dual-frequency precipitation radar to fly with other radars still in orbit (TRMM, CloudSat).

No long data sets to which sensor data could be attached.

Decade-long record of precipitation radar and other TRMM data.

No operational experience with data.

Operational experience with data since 1998.

NOAA scientist involvement in NASA’s 1986 workshop on TRMM, and NOAA scientist participation on the TRMM science team. However, there was no expectation (and therefore no planned activities) of operational application of TRMM data at NOAA.

Collaboration among NASA and operational agencies since 2001. NOAA involvement through attendance at annual GPM planning workshops, input on operational requirements for GPM, and participation on the Precipitation Measurement Missions science team. The GPM research plan has operational objectives, and efforts are under way to establish an effective NASA-NOAA partnership for the GPM post-launch phase.

The TRMM ground validation approach followed the traditional lines of rain rate-oriented intercomparisons with classical ground validation site set-ups.

The GPM ground validation program will include quantitative assessment of the distribution and the nature of retrieval errors.

Moist physics in operational models was not well developed.

Moist physics is evolving away from purely parameterized physics toward more explicitly resolved physics in the form of cloud-resolving models. This evolution is removing the artificial distinction between clouds and precipitation.

Data assimilation of moist physics was in its infancy.

Data assimilation of moist physics, while still in its formative stages, is progressing, and will help treat observations of clouds and precipitation as part of one combined system.

Diverse and active community of researchers experimenting with a wide variety of evolving algorithms for retrieving rainfall and related information from passive microwave radiometers.

Dedicated funding and available human resources have diminished.

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