This note is intended to serve primarily as a reference guide to users wishing to make use of the Tropical Rainfall Measuring Mission data. It covers each of the three primary rainfall instruments: the passive microwave radiometer, the precipitation radar, and the Visible and Infrared Radiometer System on board the spacecraft. Radiometric characteristics, scanning geometry, calibration procedures, and data products are described for each of these three sensors.

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The Tropical Rainfall Measuring Mission (TRMM) Sensor Package

Precipitation affects many aspects of our everyday life. It is the primary source of freshwater and has significant socioeconomic impacts resulting from natural hazards such as hurricanes, floods, droughts, and landslides. Fundamentally, precipitation is a critical component of the global water and energy cycle that governs the weather, climate, and ecological systems. Accurate and timely knowledge of when, where, and how much it rains or snows is essential for understanding how the Earth system functions and for improving the prediction of weather, climate, freshwater resources, and natural hazard events. The Global Precipitation Measurement (GPM) mission is an international satellite mission specifically designed to set a new standard for the measurement of precipitation from space and to provide a new generation of global rainfall and snowfall observations in all parts of the world every 3 h. The National Aeronautics and Space Administration (NASA) and the Japan Aerospace and Exploration Agency (JAXA) ...

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The Global Precipitation Measurement Mission

A daily gridded precipitation dataset covering a period of more than 57 yr was created by collecting and analyzing rain gauge observation data across Asia through the activities of the Asian Precipitation—Highly Resolved Observational Data Integration Towards Evaluation of Water Resources (APHRODITE) project. APHRODITE's daily gridded precipitation is presently the only long-term, continental-scale, high-resolution daily product. The product is based on data collected at 5,000–12,000 stations, which represent 2.3–4.5 times the data made available through the Global Telecommunication System network and is used for most daily gridded precipitation products. Hence, the APHRODITE project has substantially improved the depiction of the areal distribution and variability of precipitation around the Himalayas, Southeast Asia, and mountainous regions of the Middle East. The APHRODITE project now contributes to studies such as the determination of Asian monsoon precipitation change, evaluation of water resources, ...

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APHRODITE: Constructing a Long-Term Daily Gridded Precipitation Dataset for Asia Based on a Dense Network of Rain Gauges

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 dB Z) 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).

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The status of the tropical rainfall measuring mission (TRMM) after two years in orbit

Describes an outline of the algorithm that estimates the instantaneous profiles of the true radar reflectivity factor and rainfall rate from the radar reflectivity profiles observed by the precipitation radar (PR) onboard the TRMM satellite. The major challenge of the algorithm lies in the correction of rain attenuation with the non-uniform beam filling effect. The algorithm was tested with synthetic data and the result is shown.

Rain profiling algorithm for the TRMM precipitation radar

Microwave path-average measurements of rainfall attenuation at 25.35 GHz (A/sub 25H/), 38.025 GHz (A/sub 38H/), using the upgraded 2.3-km NASA TRMM microwave link, are used to estimate parameters (/spl Lambda/ and N/sub 0/-/spl mu/ fixed) of a path-average gamma drop size distribution N~(D). This dual-wavelength technique requires the computation of the forward scattering amplitude f(D) for oblate raindrops to solve for the drop size distribution parameters numerically. The resulting N~(D) is then used to compute the corresponding instantaneous rain rate, R~, which is compared to rainfall rate estimates based on empirical power law relations, and to path-average rainfall rate measurements from a network of optical and tipping bucket raingauges located beneath the link path. Rain rate estimates using link path-average polarization differential phase-shift measurements (/spl Phi//sub DP/) at 8.45 GHz are also implemented.

Path-average drop size distribution estimation from dual-wavelength measurements of attenuation

Microwave attenuation measurements at 25 GHz, and 38 GHz on the NASA/TRMM 2.3-km microwave link permit the application of a dual-wavelength inversion technique to estimate parameters of a path-average gamma drop size distribution (DSD). Three Joss-Waldvogel disdrometers provide DSD measurements under the link path permitting direct comparison with the estimated DSD. Additionally, the estimated and measured DSDs are used to compute path-average rain rates and rainfall accumulation. These results are compared to path-average measurements from the network of optical and tipping bucket rain gauges.

Estimation of path-average rain drop size distribution using the NASA/TRMM microwave link

Mobile radar platforms can provide unique observations of geophysical phenomena for scientific research and for operational applications such as reconnaissance and flight safety. The advantages of an airborne or spaceborne radar are obvious; the radars provide 1) observations where it is often impractical or too costly to place a ground-based radar (e. g., over the oceans or mountains), 2) surveillance over a large area or over a long time period when the system of interest is moving, 3) the ability to adjust viewing angles to minimize uncertainties due to viewing geometry, for example, along a dual-Doppler baseline; and 4) measurements to complement coincident observations from other remote and in situ sensors.

Airborne/spaceborne radar - Panel report

A rain-rate range-profiling algorithm has been developed for 'standard' data processing of TRMM Precipitation Radar (PR). Major challenges in the algorithm include the corrections for the effects of rain attenuation and non-uniform beam filling (NUBF) and in the rejection of surface clutter. A combination of the Hitschfield-Bordan and surface reference methods is used to correct radar returns for the rain attenuation. The NUBF effects are estimated from the spatial variations of the estimated total path integral of attenuation from the top of rain to the surface in the vicinity of the radar beam concerned. In this paper, we first outline the range profiling algorithm. Next we show two examples of PR observation; a typhoon over Pacific and a squall line over Florida. In the Florida case, we compare the PR and ground-based radar measurements. The results indicate that this algorithm is basically working well. Further studies are needed to statistically evaluate the performance.

Preliminary test results of a rain rate profiling algorithm for the TRMM precipitation radar

This paper describes the new hybrid method adopted in the TRMM standard algorithm that estimates the vertical profiles of attenuation-corrected radar reflectivity factor and rainfall rate. The attenuation correction is based on a hybrid of the Hitschfeld-Bordan method and a surface reference method. The new hybrid algorithm assumes errors in both the surface reference and the measured rain echoes. The optimum attenuation correction factor is determined by maximizing the conditional probability of the path-integrated attenuation for a given surface reference and a measured reflectivity profile.

http://ieeexplore.ieee.org/iel5/6913/18593/00858114.pdf

Robert Meneghini

Papers

Path-average drop size distribution estimation from dual-wavelength measurements of attenuation

Estimation of path-average rain drop size distribution using the NASA/TRMM microwave link

Airborne/spaceborne radar - Panel report

Preliminary test results of a rain rate profiling algorithm for the TRMM precipitation radar

A new hybrid surface reference method for the TRMM Precipitation Radar