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Investigation of XBT and XCTD biases in the Arabian Sea and the Bay of Bengal with implications for climate studies

DRS at CSIR-National Institute of Oceanography

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Title Investigation of XBT and XCTD biases in the Arabian Sea and the Bay of Bengal with implications for climate studies
 
Creator Boyer, T.
Gopalakrishna, V.V.
Reseghetti, F.
Naik, A.
Suneel, V.
Ravichandran, M.
Ali, N.P.M.
Rafeeq, M.M.M.
Chico, R.A.
 
Subject XBTs
climatic changes
velocity profiles
temperature anomalies
 
Description Long time series of XBT data in the Bay of Bengal and the Arabian Sea are valuable datasets for exploring and understanding climate variability. However, such studies of interannual and longer-scale variability of temperature require an understanding, and, if possible, a correction of errors introduced by biases in the XBT and expendable conductivity–temperature–depth (XCTD) data. Two cruises in each basin were undertaken in 2008/09 on which series of tests of XBTs and XCTDs dropped simultaneously with CTD casts were performed. The XBT and XCTD depths were corrected by comparison with CTD data using a modification of an existing algorithm. Significant probe-to-probe fall-rate equation (FRE) velocity and deceleration coefficient variability was found within a cruise, as well as cruise-to-cruise variability. A small (;0.018C) temperature bias was also identified for XBTs on each cruise. No new FRE can be proposed for either the Bay of Bengal or the Arabian Sea for XBTs. For the more consistent XCTD, basin-specific FREs are possible for the Bay of Bengal, but not for the Arabian Sea. The XCTD FRE velocity coefficients are significantly higher than the XCTD manufacturers’ FRE coefficient or those from previous tests, possibly resulting from the influence of temperature on XCTD FRE. Mean temperature anomalies versus a long-term mean climatology for XBT data using the present default FRE have a bias (which is positive for three cruises and negative for one cruise) compared to the mean temperature anomalies for CTD data. Some improvement is found when applying newly calculated cruise-specific FREs. This temperature error must be accounted for in any study of temperature change in the regions
 
Date 2011-03-30T06:00:43Z
2011-03-30T06:00:43Z
2011
 
Type Journal Article
 
Identifier Journal of Atmospheric and Oceanic Technology, vol.28(2); 2011; 266-286
http://drs.nio.org/drs/handle/2264/3829
 
Language en
 
Rights Copyright [2011] American Meteorological Society. All efforts have been made to respect the copyright to the best of our knowledge. Inadvertent omissions, if brought to our notice, stand for correction and withdrawal of document from this repository.
 
Publisher American Meteorological Society