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Ocean water vapor and cloud liquid water trends from 1992 to 2005 TOPEX Microwave Radiometer data

Keihm, S. and Brown, S. and Teixeira, J. and Desai, S. and Lu, W. and Fetzer, E. and Ruf, C. and Huang, X. and Yung, Y. (2009) Ocean water vapor and cloud liquid water trends from 1992 to 2005 TOPEX Microwave Radiometer data. Journal of Geophysical Research D, 114 (D18). D18101. ISSN 0148-0227.

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The continuous 1992–2005 data set of the TOPEX Microwave Radiometer (TMR) has been reprocessed to provide global, zonal, and regional scale histories of overocean integrated water vapor (IWV) and cloud liquid water (CLW). Results indicate well-defined trends in IWV on global and hemisphere scales, with values of 1.8 ± 0.4%/decade (60°S–60°N), 2.4 ± 0.4%/decade (0–60°N), and 1.0 ± 0.5%/decade (0–60°S). The uncertainties represent 1 standard deviation of the regressed slope parameter adjusted for lag 1 autocorrelation. These results are comparable to earlier results based on analyses of the multiinstrument SSM/I ocean measurements beginning in 1988. For the 1992–2005 interval, comparisons between SSM/I- and TMR-derived IWV trends show remarkable agreement, with global trends differing by less than 0.3%/decade, comparable to the statistical uncertainty level and about one-sixth of the global TMR-derived trend. Latitudinal and regional analyses of IWV trends show large variability about the global mean, with synoptic scale variations of IWV trends ranging from ∼−8 to +8%/decade. Averaged over 5° latitude bands the IWV trends reveal a near zero minimum in the Southern Tropical Pacific and maximum values of ∼4%/decade over the 30–40N latitude band. Comparisons with band latitude averaged SST data over the same 1992–2005 interval roughly match a delta_IWV/delta_SST trend scaling of ∼11%/K, consistent with previously observed tropical and midlatitude seasonal variability. TMR-derived CLW trends are fractionally comparable to the IWV trends. The CLW values are 1.5 ± 0.6%/decade (60°S–60°N), 2.0 ± 0.8%/decade (0–60°N), and 1.1 ± 0.8%/decade (0–60°S). When scaled to global mean CLW derived from SSM/I and compared seasonally, the TMR CLW variations exhibit excellent tracking with the SSM/I results. Unlike IWV, however, the CLW statistical uncertainties do not likely reflect the dominant error component in the retrieved trends. The 1992–2005 CLW trend estimates were particularly sensitive to short-term trends in the first and last 2 years of the TMR archive. Additional errors difficult to quantify include strong aliasing effects from precipitation cells and uncertainties in the radiative transfer models utilized in the generation of the TMR CLW algorithm.

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Yung, Y.0000-0002-4263-2562
Additional Information:©2009 American Geophysical Union. Received 30 March 2009; accepted 5 June 2009; published 16 September 2009. The research described in this paper was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. Unnamed reviewer comments proved extremely valuable in the production of the published version of this paper.
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Subject Keywords:trends
Issue or Number:D18
Classification Code:1640 Global Change: Remote sensing (1855); 1855 Hydrology: Remote sensing (1640); 1872 Hydrology: Time series analysis (3270, 4277, 4475); 1895 Hydrology: Instruments and techniques: monitoring; 6969 Radio Science: Remote sensing
Record Number:CaltechAUTHORS:20091013-093449608
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Official Citation:Keihm, S., S. Brown, J. Teixeira, S. Desai, W. Lu, E. Fetzer, C. Ruf, X. Huang, and Y. Yung (2009), Ocean water vapor and cloud liquid water trends from 1992 to 2005 TOPEX Microwave Radiometer data, J. Geophys. Res., 114, D18101, doi:10.1029/2009JD012145.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:16303
Deposited By: George Porter
Deposited On:21 Oct 2009 20:54
Last Modified:09 Mar 2020 13:19

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