What are TRMM and GPM?

TRMM publications

Kwajalein Ground Validation (opens new page)

KWAJEX (opens new page)

GPM publications

OLYMPEX publications (opens new page)


What are TRMM and GPM?

TRMMThe Tropical Rainfall Measuring Mission (TRMM) was a joint mission between NASA and the National Space Development Agency (NASDA) of Japan to study tropical rainfall and the vertical gradient of heating caused by precipitating cloud systems. The TRMM satellite was launched 27 November 1997 in an orbit between 35S and 35N latitudes. It continued its mission in orbit until 15 April 2015. The instrumentation on board TRMM included a Ku-band radar, the first-ever quantitative spaceborne Precipitation Radar (PR). rainfall averages TRMMOnboard TRMM also was a multi-channel passive Microwave Radiometer (TMI), a Visible and Infrared Scanner (VIRS), a Cloud and Earth Radiant Energy System (CERES), and a Lightning Imaging Sensor (LIS). The TMI operated with five channels (10.65, 19.35, 21.3, 37.0, and 85.5 GHz), which allowed precipitation detection over both land and ocean.

GPMSucceeding TRMM is the Global Precipitation Measurement (GPM) Core Observatory satellite, launched 27 February 2014. Whereas TRMM was restricted to the tropics and subtropics, GPM orbits between 65S and 65N so that midlatitude precipitation is now measured by the satellite's instruments. One of the prime instruments onboard the GPM Core Observatory is the Dual-frequency Precipitation Radar (DPR). The DPR consists of a Ku-band precipitation radar (KuPR) and a Ka-band precipitation radar (KaPR). The KuPR (13.6 GHz) is an updated version of the TRMM PR. The inclusion GPMof the Ka-band radar improves the radar sensitivity so that weaker echoes are now detected. Another key instrument is the GPM Microwave Imager (GMI), which is a multi-channel, conically scanning, microwave radiometer with thirteen microwave channels ranging in frequency from 10 GHz to 183 GHz. The higher passive microwave frequencies are for the detection of snow. In addition to carrying channels similar to those on the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI), the GMI carries four high frequency, millimeter-wave channels of 166 GHz and 183 GHz. With a 1.2 m diameter antenna, the GMI provides significantly improved spatial resolution over TMI.


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Houze, R. A., Jr., and C. A. Leary, 1976: Comparison of convective mass and heat transports in tropical easterly waves computed by two methods. J. Atmos. Sci., 33, 424-429.

Schumacher, C., and R. A. Houze, Jr., 2000: Comparison of radar data from the TRMM satellite and Kwajalein oceanic validation site. J. Appl. Meteor., 39, 2151-2164.

Convective precipitation case observed at 0251 UTC 25 Nov 1998. (From Schumacher and Houze 2000, Figure 4.) Map of the Kwajalein area centered on the KR. (From Schumacher and Houze 2000, Figure 1.)

Schumacher, C., and R. A. Houze, Jr., 2003a: Stratiform rain in the tropics as seen by the TRMM Precipitation Radar. J. Climate, 16, 1739-1756.

The PR total rain. (From Schumacher and Houze 2003a, Figure 3a.)

Schumacher, C., and R. A. Houze, Jr., 2003b: The TRMM Precipitation Radar’s view of shallow, isolated rain. J. Appl. Meteor., 42, 1519-1524.

Houze, R. A., Jr., S. Brodzik, C. Schumacher, S. E. Yuter, and C. R. Williams, 2004: Uncertainties in oceanic radar rain maps at Kwajalein and implications for satellite validation. J. Appl. Meteor., 43, 1114-1132.

Kim, M.-J., J. A. Weinman, and R. A. Houze, Jr., 2004: Validation of maritime rainfall retrievals from the TRMM-microwave radiometer. J. Appl. Meteor., 43, 847-859.

Kwajalein and neighboring atoll islands with KWAJEX sensors. (From Yuter et al. 2005, Figure 2.)

Yuter, S. E., R. A. Houze, Jr., E. A. Smith, T. T.Wilheit, and E. Zipser, 2005: Physical characterization of tropical oceanic convection observed in KWAJEX. J. Appl. Meteor., 44, 385-415.

Clouds observed from the roof of the Kwajalein weather station. (From Yuter et al. 2005, Figure 18b.)

Cetrone, J., and R. A. Houze, Jr., 2006: Characteristics of tropical convection over the ocean near Kwajalein. Mon. Wea. Rev., 134, 834-853.

PR-observed monthly rain amount for MAM. (From Schumacher and Houze 2005, Figure 3a.)

Schumacher, C., and R. A. Houze, Jr., 2006: Stratiform precipitation production over sub-Saharan Africa and the tropical East Atlantic as observed by TRMM. Quart. J. Roy. Meteor. Soc., 132, 2235-2255.


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