Retrieval of monthly rainfall over oceans from the Special Sensor Microwave/Imager (SSM/I) /
The Tropical Rainfall Measuring Mission (TRMM) satellite will
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1994.
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| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=741965521&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | The Tropical Rainfall Measuring Mission (TRMM) satellite will be launched in 1997. The TRMM payloads will include the TRMM Microwave Imager (TMI) which is essentially a copy of the SSM/I with a dual-polarized pair of 10.7 GHz channels added. One of principal goals of TRMM is to determine the distribution and variability of rainfall and latent-heat release on a monthly, 5' x 50 average basis over the tropical oceans. For this purpose, a physical/statistical monthly rainfall retrieval algorithm has been developed. Instantaneous rain rates are estimated from brightness temperatures using rw'n rate - brightness temperature (R-T) relationships derived from a radiative transfer model. First, the freezing level is estimated from a combination of 19 and 22 GHz brightness temperatures. Using this freezing level, rain rates are estimated using each of the 19 and 37 GHz brightness temperatures which are Joined into a composite best estimate of the rain rate and then adjusted for beamfilling error by a multiplicative factor generated from simulation studies. Histograms of the instantaneous rain rates generated are collected in 5' x 5' boxes over oceans for each month. A mixed lognormal distribution with unspecified coefficients is determined,by fitting the observed distribution to the lognormal form using the maximum likelihood estimate method. Since only a portion of the measurement dynamic range is reliably estimated from these measurements, the fit is likewise limited to the reliable portion of the dynamic range. With the frequency range from 19 to 37 GHz, this dynamic range is approximately 1 to 20 mm/hr. Comparison between the monthly rainfall estimated from the SSM/I and Pacific atoll data indicates that the algorithm works very well in tropical area. Although this algorithm is tested on SSM/I data, it is also suited for TRMM data, which should have a larger dynamic range with 10.7 GHz ch annels added. Daily rainfall is computed using SSM/I data from January to December 1989 to investigate the evidence of a 30 - 60 day oscillation. Spectral analysis of daily rainfall shows that the strongest 30 - 60 day rainfall oscillations are located from 5'S to 5'N and extend from about 60'E to 180'. The oscillation propagates eastward at a speed of approximately 4 ms-1 along the equatorial Indian-western Pacific Ocean area. Northward propagation at a speed of about 1.5 ms-1 is also detected from 15'S to 30'N over the Indian Ocean between early May and late July. |
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| Item Description: | Vita. "Major Subject: Meteorology". |
| Physical Description: | xii, 131 leaves : illustrations, maps ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references. |