Tropical Rainfall Measuring Mission Rainfall Research Articles

Retrieved Vertical Profiles of Latent Heat Release Using TRMM Rainfall Products for February 1998**

This paper represents the first attempt to use Tropical Rainfall Measuring Mission (TRMM) rainfall information to estimate the four-dimensional latent heating structure over the global Tropics for one month (February 1998). The mean latent heating profiles over six oceanic regions [Tropical Ocean and Global Atmosphere (TOGA) Coupled Ocean–Atmosphere Response Experiment (COARE) Intensive Flux Array (IFA), central Pacific, South Pacific Convergence Zone (SPCZ), east Pacific, Indian Ocean, and Atlantic Ocean] and three continental regions (South America, central Africa, and Australia) are estimated and studied. The heating profiles obtained from the results of diagnostic budget studies over a broad range of geographic locations are used to provide comparisons and indirect validation for the heating algorithm–estimated heating profiles. Three different latent heating algorithms, the Goddard Space Flight Center convective–stratiform heating (CSH), the Goddard profiling (GPROF) heating, and the hydrometeor heating (HH) algorithms are used and their results are intercompared. The horizontal distribution or patterns of latent heat release from the three different heating retrieval methods are very similar. They all can identify the areas of major convective activity [i.e., a well-defined Intertropical Convergence Zone (ITCZ) in the Pacific, a distinct SPCZ] in the global Tropics. The magnitudes of their estimated latent heating release are also in good agreement with each other and with those determined from diagnostic budget studies. However, the major difference among these three heating retrieval algorithms is the altitude of the maximum heating level. The CSH algorithm–estimated heating profiles only show one maximum heating level, and the level varies among convective activity from various geographic locations. These features are in good agreement with diagnostic budget studies. A broader maximum of heating, often with two embedded peaks, is generally derived from applications of the GPROF heating and HH algorithms, and the response of the heating profiles to convective activity is less pronounced. Also, GPROF and HH generally yield heating profiles with a maximum at somewhat lower altitudes than CSH. The impact of different TRMM Microwave Imager (TMI) and precipitation radar (PR) rainfall information on latent heating structures was also examined. The rainfall estimated from the PR is smaller than that estimated from the TMI in the Pacific (TOGA COARE IFA, central Pacific, SPCZ, and east Pacific) and Indian Oceans, causing weaker latent heat release in the CSH algorithm–estimated heating. In addition, the larger stratiform amounts derived from the PR over South America and Australia consequently lead to higher maximum heating levels. Sensitivity tests addressing the appropriate selection of latent heating profiles from the CSH lookup table were performed.

The Status of the Tropical Rainfall Measuring Mission (TRMM) after Two Years in Orbit

The Tropical Rainfall Measuring Mission (TRMM) satellite was launched on 27 November 1997, and data from all the instruments first became available approximately 30 days after the launch. Since then, much progress has been made in the calibration of the sensors, the improvement of the rainfall algorithms, and applications of these results to areas such as data assimilation and model initialization. The TRMM Microwave Imager (TMI) calibration has been corrected and verified to account for a small source of radiation leaking into the TMI receiver. The precipitation radar calibration has been adjusted upward slightly (by 0.6 dBZ) to match better the ground reference targets; the visible and infrared sensor calibration remains largely unchanged. Two versions of the TRMM rainfall algorithms are discussed. The at-launch (version 4) algorithms showed differences of 40% when averaged over the global Tropics over 30-day periods. The improvements to the rainfall algorithms that were undertaken after launch are presented, and intercomparisons of these products (version 5) show agreement improving to 24% for global tropical monthly averages. The ground-based radar rainfall product generation is discussed. Quality-control issues have delayed the routine production of these products until the summer of 2000, but comparisons of TRMM products with early versions of the ground validation products as well as with rain gauge network data suggest that uncertainties among the TRMM algorithms are of approximately the same magnitude as differences between TRMM products and ground-based rainfall estimates. The TRMM field experiment program is discussed to describe active areas of measurements and plans to use these data for further algorithm improvements. In addition to the many papers in this special issue, results coming from the analysis of TRMM products to study the diurnal cycle, the climatological description of the vertical profile of precipitation, storm types, and the distribution of shallow convection, as well as advances in data assimilation of moisture and model forecast improvements using TRMM data, are discussed in a companion TRMM special issue in the Journal of Climate (1 December 2000, Vol. 13, No. 23).