Statistics of TRMM Data Archive and Distribution at the Goddard DAAC (original) (raw)

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

Journal of Applied Meteorology, 2000

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

On the Tropical Rainfall Measuring Mission (TRMM)

Meteorology and Atmospheric Physics, 1996

Recognizing the importance of rain in the tropics and the accompanying latent heat release, NASA for the U.S. and NASDA for Japan have partnered in the design, construction and flight of an Earth Probe satellite to measure tropical rainfall and calculate the associated heal_g. Primary mission goals are 1) the understanding of crucial links in climate variability by the hydrological cycle, 2) improvement in the large-scale models of weather and climate 3) Improvement in understanding cloud ensembles and their impacts on larger scale circulations. The linkage with the tropical oceans and landmasses are also emphasized. The Tropical Rainfall Measuring Mission (TRMM) satellite was launched in November 1997 with fuel enough to Obtain a four to five year data set of rainfall over the global tropics from 37°N to 37°S. This paper reports progress from launch date through the spring of 1999. The data system and its products and their access is described, as are the algorithms used to obtain the data. Some exciting early results from TRMM are described. Some important algorithm improvements are shown. These will be used in the first total data reprocessing, scheduled to be complete in early 2000. The reader is given information on how to access and use the data. Although tropical precipitation is organized on the mesoscale, it is noteworthy that primary objectives of the mission were to help improve climate models and aid them in climate prediction. The TRMM Project TRMM is a joint project between the United States and Japan, with the participation of many other nations in the science and validation. These include Australia, France, Germany, Israel and Thailand. A Science Steering Group outlined the proposed science and instrumentation during a joint feasibility study in the United States and Japan. This was completed in 1988 [1]. Because of funding delays; the actual TRMM Project did not start until 1991. Japan supplied the crucial new instrument (rain radar) and the launch vehicle, while the United States supplied the other four i.nstr_lments and the sp__cecrafF_. The Proiect kept a tight schedule within limited budget and TRMM was successfully launched in November 1997.

The Tropical Rainfall Measuring Mission (TRMM) Progress Report

Recognizing the importance of rain in the tropics and the accompanying latent heat release, NASA for the U.S. and NASDA for Japan have partnered in the design, construction and flight of an Earth Probe satellite to measure tropical rainfall and calculate the associated heating. Primary mission goals are 1) the understanding of crucial links in climate variability by the hydrological cycle, 2) improvement in the large-scale models of weather and climate 3) Improvement in understanding cloud ensembles and their impacts on larger scale circulations. The linkage with the tropical oceans and landmasses are also emphasized. The Tropical Rainfall Measuring Mission (TRMM) satellite was launched in November 1997 with fuel enough to obtain a four to five year data set of rainfall over the global tropics from 37°N to 37°S. This paper reports progress from launch date through the spring of 1999. The data system and its products and their access is described, as are the algorithms used to obtain the data. Some exciting early results from TRMM are described. Some important algorithm improvements are shown. These will be used in the first total data reprocessing, scheduled to be complete in early 2000. The reader is given information on how to access and use the data. 1. Introduction The Tropical Rainfall Measuring Mission ffRMM) satellite has yielded important interim results after nearly two years of successful flight operations since launch in late 1997. This paper summarizes the mission science goals, instruments, algorithm development; some early results using the "at launch" algorithms, as well as ongoing efforts to validate the TRMM products. Section 2 contains the mission science goals, a brief summary of the joint project between Japan and the United States, and a table of the instruments. Section 3 describes the selected TRMM products, the algorithms developed to obtain the products, and the TRMM data system. Section 4 is a progress report on validation efforts. Section 5 presents some highlights of TRMM products during the first months after launch and their use in several research activities. Section 6 furnishes a brief overview of the planned satellite system (Global Precipitation Mission) to succeed TRMM in measuring precipitation from space. Section 7 contains concluding remarks for this stage of the mission's lifetime. 2. The goals, the TRMM Project and the Instrument complement 2.1 The importance of tropical rainfall: TRMM goals Tropical rainfall is important in the hydrological cycle and to the lives and welfare of humans. Three-fourths of the energy that drives the atmospheric wind circulation comes from the latent heat released by tropical precipitation. It varies greatly in space and time. Often severe droughts are succeeded by deadly floods. Many scales are involved in the rain processes and their impacts on global circulations. The rain-producing cloud systems may last several hours or days. Their dimensions range from 10 km to several hundred km, so that they cannot yet be treated explicitly in the large-scale weather and climate models. Until the end of 1997, precipitation in the global tropics was not known to within a factor of two. Regarding "global warming", the various large-scale models differed among themselves in the predicted magnitude of the warming and in the expected regional effects of these temperature and moisture changes. Accurate estimates of tropical precipitation and the associated latent heat release were urgently needed to improve these models. The agreed upon science goals of TRMM as presented in the first major report (Simpson, Ed., 1988) are shown in Table 2.1 9/9/99 3:03 PM IV. TO HELP UNDERSTAND, DIAGNOSE AND PREDICT THE ONSET AND DEVELOPMENT OF THE EL NINO, SOUTHERN OSCILLATION AND THE PROPAGATION OF THE 30-60 DAY OSCILLATION IN THE TROPICS V. TO HELP UNDERSTAND THE EFFECT THAT RAINFALL HAS ON THE OCEAN THERMOHALINE CIRCULATIONS & THE STRUCTURE OF THE UPPER OCEAN VI. TO ALLOW CROSS-CALIBRATION BETWEEN TRMM AND OTHER SENSORS WITH LIFE EXPECTANCIES BEYOND THAT OF TRMM ITSELF. VII. TO EVALUATE THE DIURNAL VARIABILITY OF TROPICAL RAINFALL GLOBALLY VIII. TO EVALUATE A SPACE-BASED SYSTEM FOR RAINFALL MEASUREMENT 2.2 The TRMM instruments To meet the science goals, within limited resources, the final instruments are shown in Table 2.2.1. Their scanning patterns are illustrated in Figure 2.2.1. passive microwave instruments would thus be able calibrate the surface rain estimations made empirically from operational geosynchronous IR sensors. Using this method with geosynchronous products obviated the restricted sampling by TRMM alone, which would overfly a given 5°by 5°grid box only about twice in 24 hr. The radar and radiometer combination enables high quality precipitation profiles. The small cloud drops that play an integral part in the latent heat release process, however, would not be observable with sufficient accuracy to construct profiles of the latent heat release. It was therefore planned from the start to use results of a cloud-resolving numerical model in retrieving the important latent heat profiles.

The TRMM Multi-Satellite Precipitation Analysis (TMPA)

Springer eBooks, 2009

The Tropical Rainfall Measuring Mission (TRMM) Multi-satellite Precipitation Analysis (TMPA) is intended to provide a "best" estimate of quasi-global precipitation from the wide variety of modern satellite-borne precipitation-related sensors. Estimates are provided at relatively fine scales (0.25°x0.25°, 3-hourly) in both real and post-real time to accommodate a wide range of researchers. However, the errors inherent in the finest scale estimates are large. The most successful use of the TMPA data is when the analysis takes advantage of the fine-scale data to create time/space averages appropriate to the user's application. We review the conceptual basis for the TMPA, summarize the processing sequence, and focus on two new activities. First, a recent upgrade to the real-time version incorporates several additional satellite data sources and employs monthly climatological adjustments to approximate the bias characteristics of the research quality post-real-time product. Second, an upgrade of the research quality post-real-time TMPA from Version 6 to Version 7 (in beta test at press time) is designed to provide a variety of improvements that increase the list of input data sets and correct several issues. Future enhancements for the TMPA will include improved error estimation, extension to higher latitudes, and a shift to a Lagrangian time interpolation scheme.

Status of TRMM Monthly Estimates of Tropical Precipitation

Meteorological Monographs, 2003

Three years of Tropical Rainfall Measuring Mission (TRMM) monthly estimates of tropical surface rainfall are analyzed to document and understand the differences among the TRMM-based estimates and how these differences relate to the pre-TRMM estimates and current operational analyses. Variation among the TRMM estimates is shown to be considerably smaller than among a pre-TRMM collection of passive microwave-based products. Use of both passive and active microwave techniques in TRMM should lead to increased confidence in converged estimates. Current TRMM estimates are shown to have a range of about 20% for the tropical ocean as a whole, with variations in heavily raining ocean areas of the Intertropical Convergence Zone (ITCZ) and South Pacific Convergence Zone (SPCZ) having differences over 30%. In midlatitude ocean areas the differences are smaller. Over land there is a distinct difference between the Tropics and midlatitude with a reversal between some of the products as to which tends to be relatively high or low. Comparisons of TRMM estimates with ocean atoll and land rain gauge information point to products that might have significant regional biases. The bias of the radar-based product is significantly low compared with atoll rain gauge data, while the passive microwave product is significantly high compared to rain gauge data in the deep Tropics. The evolution of rainfall patterns during the recent change from intense El Nino to a long period of La Nina and then a gradual return to near neutral conditions is described using TRMM. The time history of integrated rainfall over the tropical oceans (and land) during this period differs among the passive and active microwave TRMM estimates.

Tropical Rainfall Distributions Determined Using TRMM Combined with Other Satellite and Rain Gauge Information

Journal of Applied Meteorology, 2000

A technique is described to use Tropical Rainfall Measuring Mission (TRMM) combined radar-radiometer information to adjust geosynchronous infrared satellite data [the TRMM Adjusted Geostationary Operational Environmental Satellite Precipitation Index (AGPI)]. The AGPI is then merged with rain gauge information (mostly over land) to provide finescale (1Њ latitude ϫ 1Њ longitude) pentad and monthly analyses, respectively. The TRMM merged estimates are 10% higher than those from the Global Precipitation Climatology Project (GPCP) when integrated over the tropical oceans (37ЊN-37ЊS) for 1998, with 20% differences noted in the most heavily raining areas. In the dry subtropics the TRMM values are smaller than the GPCP estimates. The TRMM merged product tropical-mean estimates for 1998 are 3.3 mm day Ϫ1 over ocean and 3.1 mm day Ϫ1 over land and ocean combined. Regional differences are noted between the western and eastern Pacific Ocean maxima when TRMM and GPCP are compared. In the eastern Pacific rain maximum the TRMM and GPCP mean values are nearly equal, which is very different from the other tropical rainy areas where TRMM merged product estimates are higher. This regional difference may indicate that TRMM is better at taking into account the vertical structure of the rain systems and the difference in structure between the western and eastern (shallower) Pacific convection. Comparisons of these TRMM merged analysis estimates with surface datasets shows varied results; the bias is near zero when compared with western Pacific Ocean atoll rain gauge data, but is significantly positive as compared with Kwajalein radar estimates (adjusted by rain gauges). Over land the TRMM estimates also show a significant positive bias. The inclusion of gauge information in the final merged product significantly reduces the bias over land, as expected. The monthly precipitation patterns produced by the TRMM merged data process clearly show the evolution of the El Niño-Southern Oscillation (ENSO) tropical precipitation pattern from early 1998 (El Niño) to early 1999 (La Niña) and beyond. The El Niño-minus-La Niña difference map shows the expected eastern Pacific maximum, the ''Maritime Continent'' minima, and other tropical and midlatitude features, very similar to those detected by the GPCP analyses. However, summing the El Niño-minus-La Niña differences over the global tropical oceans yields divergent answers for interannual changes from TRMM, GPCP, and other estimates. This emphasizes the need for additional validation and analysis before it is feasible to understand the relations between global precipitation anomalies and Pacific Ocean ENSO temperature changes.