A new approach for the determination of the drag coefficient from the upper ocean response to a tropical cyclone: A feasibility study

Sarah Zedler; Guido Kanschat; Robert L. Korty; Ibrahim Hoteit

doi:10.1007/s10872-011-0092-6

A new approach for the determination of the drag coefficient from the upper ocean response to a tropical cyclone: A feasibility study

Sarah Zedler, Guido Kanschat, Robert L. Korty, Ibrahim Hoteit

Research output: Contribution to journal › Article › peer-review

12 Scopus citations

Abstract

We seek to determine if a small number of measurements of upper ocean temperature and currents can be used to make estimates of the drag coefficient that have a smaller range of uncertainty than previously found. We adopt a numerical approach using forward models of the ocean's response to a tropical cyclone, whereby the probability density function of drag coefficient values as a function of wind speed that results from adding realistic levels of noise to the simulated ocean response variables is sought. Allowing the drag coefficient two parameters of freedom, namely the values at 35 and at 45 m/s, we found that the uncertainty in the optimal value is about 20% for levels of instrument noise up to 1 K for a misfit function based on temperature, or 1.0 m/s for a misfit function based on 15 m velocity components. This is within tolerable limits considering the spread of measurement-based drag coefficient estimates. The results are robust for several different instrument arrays; the noise levels do not decrease by much for arrays with more than 40 sensors when the sensor positions are random. Our results suggest that for an ideal case, having a small number of sensors (20-40) in a data assimilation problem would provide sufficient accuracy in the estimated drag coefficient. © 2011 The Oceanographic Society of Japan and Springer.

Original language	English (US)
Pages (from-to)	227-241
Number of pages	15
Journal	Journal of Oceanography
Volume	68
Issue number	2
DOIs	https://doi.org/10.1007/s10872-011-0092-6
State	Published - Dec 30 2011

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): KUS-C1-016-04
Acknowledgements: This publication was based on work supported by award no. KUS-C1-016-04, made by King Abdullah University of Science and Technology (KAUST). I would like to thank Peter Niiler and the other PIs on the Coupled Boundary Layer Air-Sea Transfer Experiment for designing the field experiment that motivated this study. Thanks to Gerry Creager and Guy Almes for providing computer support. We would like to acknowledge three anonymous reviewers for very helpful comments on an earlier draft of this paper. Additionally, we thank statisticians Cornelis Potgieter and Avishek Charkraborty (who specializes in Bayesian techniques) for reviewing our methodology and providing helpful commentary.

ASJC Scopus subject areas

Oceanography

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10.1007/s10872-011-0092-6

Cite this

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title = "A new approach for the determination of the drag coefficient from the upper ocean response to a tropical cyclone: A feasibility study",

abstract = "We seek to determine if a small number of measurements of upper ocean temperature and currents can be used to make estimates of the drag coefficient that have a smaller range of uncertainty than previously found. We adopt a numerical approach using forward models of the ocean's response to a tropical cyclone, whereby the probability density function of drag coefficient values as a function of wind speed that results from adding realistic levels of noise to the simulated ocean response variables is sought. Allowing the drag coefficient two parameters of freedom, namely the values at 35 and at 45 m/s, we found that the uncertainty in the optimal value is about 20% for levels of instrument noise up to 1 K for a misfit function based on temperature, or 1.0 m/s for a misfit function based on 15 m velocity components. This is within tolerable limits considering the spread of measurement-based drag coefficient estimates. The results are robust for several different instrument arrays; the noise levels do not decrease by much for arrays with more than 40 sensors when the sensor positions are random. Our results suggest that for an ideal case, having a small number of sensors (20-40) in a data assimilation problem would provide sufficient accuracy in the estimated drag coefficient. {\textcopyright} 2011 The Oceanographic Society of Japan and Springer.",

author = "Sarah Zedler and Guido Kanschat and Korty, {Robert L.} and Ibrahim Hoteit",

note = "KAUST Repository Item: Exported on 2020-10-01 Acknowledged KAUST grant number(s): KUS-C1-016-04 Acknowledgements: This publication was based on work supported by award no. KUS-C1-016-04, made by King Abdullah University of Science and Technology (KAUST). I would like to thank Peter Niiler and the other PIs on the Coupled Boundary Layer Air-Sea Transfer Experiment for designing the field experiment that motivated this study. Thanks to Gerry Creager and Guy Almes for providing computer support. We would like to acknowledge three anonymous reviewers for very helpful comments on an earlier draft of this paper. Additionally, we thank statisticians Cornelis Potgieter and Avishek Charkraborty (who specializes in Bayesian techniques) for reviewing our methodology and providing helpful commentary.",

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N1 - KAUST Repository Item: Exported on 2020-10-01 Acknowledged KAUST grant number(s): KUS-C1-016-04 Acknowledgements: This publication was based on work supported by award no. KUS-C1-016-04, made by King Abdullah University of Science and Technology (KAUST). I would like to thank Peter Niiler and the other PIs on the Coupled Boundary Layer Air-Sea Transfer Experiment for designing the field experiment that motivated this study. Thanks to Gerry Creager and Guy Almes for providing computer support. We would like to acknowledge three anonymous reviewers for very helpful comments on an earlier draft of this paper. Additionally, we thank statisticians Cornelis Potgieter and Avishek Charkraborty (who specializes in Bayesian techniques) for reviewing our methodology and providing helpful commentary.

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A new approach for the determination of the drag coefficient from the upper ocean response to a tropical cyclone: A feasibility study

Abstract

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