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Rainfall over oceans inferred from Nimbus 7 SMMR - Application to 1982-83 El NinoNimbus 7 Scanning Multichannel Microwave Radiometer (SMMR) measurements at five frequencies in the region 6.6 to 37 GHz, at a resolution of 155 km, are analyzed to infer precipitation over the global oceans. The microwave data show, on this spatial scale, that the combined liquid water in the clouds and rain increases the brightness temperature almost linearly with frequency in the 6.6-18-GHz region, while at 37 GHz such a simple relationship is not noticed. Further, as the atmospheric water-vapor absorption and the effects of scattering by precipitation particles are relatively weak at 6.6 and 10.7 GHz, a technique to remotely sense the liquid water content in the atmosphere is developed based on the brightness measurements at these two frequencies. Seasonal mean patterns of liquid water content in the atmosphere derived from SMMR over global oceans relate closely to climatological patterns of precipitation. Based on this, an empirical relationship is derived to estimate precipitation over the global oceans, with an accuracy of about + or - 30 percent, on a seasonal basis from satellite measurements made during the three years (1979-81) before the recent El Nino event. The deviations from these three-year means, in the precipitation, produced by the 1982-83 el Nino event are then deduced from the SMMR measurements. In the Pacific, the precipitation over the ITCZ in the north, the South Pacific Convergence Zone, and the oceans around Indonesia is drastically reduced. At the same time a substantial increase in precipitation is observed over the normally dry central and eastern equatorial Pacific Ocean.
Document ID
19870040747
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Prabhakara, C.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Short, D. A.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Wiscombe, W.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Fraser, R. S.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Vollmer, B. E.
(Applied Research Corp. Landover, MD, United States)
Date Acquired
August 13, 2013
Publication Date
October 1, 1986
Publication Information
Publication: Journal of Climate and Applied Meteorology
Volume: 25
ISSN: 0733-3021
Subject Category
Meteorology And Climatology
Accession Number
87A28021
Distribution Limits
Public
Copyright
Other

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