An inclined orbit extending between 35°N and 35°S at 350-km altitude was found to be most suitable. Several orbits and altitudes were considered.
#Radiant defense mission 12 series#
The radar data from the four Global Atmospheric Research Program Atlantic Tropical Experiment ships stationed in the intertropical convergence zone (ITCZ) off Africa in 1974 were used for a series of sampling studies. The low Earth orbit needed to realize such measurements from a spaceborne platform, however, immediately raised concerns regarding the sampling adequacy of such a satellite. 1992) suggested that instrument accuracy was promising. Joint aircraft flights with an experimental radar ( Meneghini et al. Fugono, joined in the activities soon thereafter. Japan’s Communications Laboratory, then headed by Dr. Theon at NASA Headquarters by a team of Goddard Space Flight Center investigators consisting of Drs. By September 1984, a proposal titled, “Tropical Rain Measuring Mission,” was submitted to Dr. The idea of measuring rainfall from space using a combined instrument complement of passive and active microwave (radar) instruments was generated in the early 1980s. Accurate estimates of tropical precipitation were desperately needed to validate and to gain confidence in these models.
In regard to “global warming,” the various large-scale models differed among themselves in the predicted magnitude of the warming, distribution, and amount of tropical precipitation and in the expected regional effects of these temperature and moisture changes. Until the end of 1997, precipitation in the global Tropics was still very uncertain, with large numbers of infrared and passive microwave algorithms providing very diverse estimates. Yet, it often lasts no longer than a few hours at a time. Tropical rainfall oscillates wildly between severe droughts and occasional deadly floods. Precipitation, unfortunately, is one of the most difficult atmospheric parameters to measure because of the large variations in space and time. Three-fourths of the energy that drives the atmospheric wind circulation comes from the latent heat released by tropical precipitation. Tropical rainfall is important in the hydrological cycle and to the lives and welfare of humans. Motivation and history of the Tropical Rainfall Measuring Mission (TRMM) 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.
The TRMM field experiment program is discussed to describe active areas of measurements and plans to use these data for further algorithm improvements. 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 ground-based radar rainfall product generation is discussed. 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 at-launch (version 4) algorithms showed differences of 40% when averaged over the global Tropics over 30-day periods. Two versions of the TRMM rainfall algorithms are discussed. 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. The TRMM Microwave Imager (TMI) calibration has been corrected and verified to account for a small source of radiation leaking into the TMI receiver. 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 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.
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