IES Calibration and Mapping Procedures.

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Bibliographic Details
Title:	IES Calibration and Mapping Procedures.
Authors:	Tracey, Karen L., Howden, Stephan D., Watts, D. Randolph
Source:	Journal of Atmospheric & Oceanic Technology. Dec97, Vol. 14 Issue 6, p1483. 11p.
Subjects:	Ocean, Forecasting, Calibration, Gulf Stream
Abstract:	The procedures used in the Synoptic Ocean Prediction experiment for calibration of inverted echo sounder (IES) travel time τ data have led to substantially improved accuracy. In previous work, τ was converted to main thermocline depth Z[subT] using point measurements of the 12°C depth from coincident expendable bathythermograph (XBT) casts. The new method presented in this study vertically integrates the XBT temperature to produce the quantity Q[subT], which is very tightly related to τ. The advantage of this method is that the calibration constants have roughly half the uncertainty obtained with the traditional method. Seasonal changes in τ determined from hydrographic data in the Gulf Stream region were found to vary with geographic region; near 68°W τ changed by 1.8 ms from March to September, whereas near Cape Hatteras the annual change was only 1.0 ms. The fully calibrated IES Z[sup*][subT] has an estimated error of 19 m (one standard deviation). An iterative optimal interpolation scheme is described, by which the Gulf Stream thermocline depth was mapped on a two-dimensional grid. Initially, daily maps were generated using established mapping techniques. Subsequently, these maps were averaged for 31-day periods and in turn used as the new 'mean fields' for the final maps. Verification of the mapped fields against independent XBT data gives rms differences of 31-46 m, which is only 3%-5% of the 900-m range of the observed... [ABSTRACT FROM AUTHOR]
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Database:	Engineering Source

Description
Abstract:	The procedures used in the Synoptic Ocean Prediction experiment for calibration of inverted echo sounder (IES) travel time τ data have led to substantially improved accuracy. In previous work, τ was converted to main thermocline depth Z[subT] using point measurements of the 12°C depth from coincident expendable bathythermograph (XBT) casts. The new method presented in this study vertically integrates the XBT temperature to produce the quantity Q[subT], which is very tightly related to τ. The advantage of this method is that the calibration constants have roughly half the uncertainty obtained with the traditional method. Seasonal changes in τ determined from hydrographic data in the Gulf Stream region were found to vary with geographic region; near 68°W τ changed by 1.8 ms from March to September, whereas near Cape Hatteras the annual change was only 1.0 ms. The fully calibrated IES Z[sup*][subT] has an estimated error of 19 m (one standard deviation). An iterative optimal interpolation scheme is described, by which the Gulf Stream thermocline depth was mapped on a two-dimensional grid. Initially, daily maps were generated using established mapping techniques. Subsequently, these maps were averaged for 31-day periods and in turn used as the new 'mean fields' for the final maps. Verification of the mapped fields against independent XBT data gives rms differences of 31-46 m, which is only 3%-5% of the 900-m range of the observed... [ABSTRACT FROM AUTHOR]
ISSN:	07390572
DOI:	10.1175/1520-0426(1997)014<1483:ICAMP>2.0.CO;2