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Comparison of a simple logarithmic and equivalent neutral wind approaches for converting buoy-measured wind speed to the standard height: Special emphasis to North Indian Ocean

Singh, P and Parekh, A and Attada, R (2013) Comparison of a simple logarithmic and equivalent neutral wind approaches for converting buoy-measured wind speed to the standard height: Special emphasis to North Indian Ocean. Theoretical and Applied Climatology, 111 (3-4). pp. 455-463. ISSN 0177-798X

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Abstract

The difference between the transferred wind speed to 10-m height based on the equivalent neutral wind approach (Un) and the logarithmic approach (Ulog) is studied using in situ observations from the Indian, Pacific, and Atlantic Oceans, with special emphasis given to the North Indian Ocean. The study included Un - Ulog variations with pressure, relative humidity, wind speed, air temperature, and sea surface temperature (SST). Un - Ulog variation with respect to air temperature (Ta) reveals that Un - Ulog is out of phase with air temperature. Further analysis found that Un - Ulog is in phase with SST (Ts) - Ta and varies between -1.0 and 1.0 m/s over the North Indian Ocean, while for the rest of the Oceans, it is between -0.3 and 0.8 m/s. This higher magnitude of Un - Ulog over the North Indian Ocean is due to the higher range of Ts - Ta (-4 to 6 °C) in the North Indian Ocean. Associated physical processes suggested that the roughness length and friction velocity dependence on the air-sea temperature difference contributes to the Un - Ulog difference. The study is further extended to evaluate the behavior of Un - Ulog under cyclonic conditions (winds between 15 and 30 m/s), and it was found that the magnitude of Un - Ulog varies 0. 5-1. 5 m/s under the cyclonic wind conditions. The increasing difference with the wind speed is due to the increase in the momentum transfer coefficient with wind speed, which modifies the friction velocity significantly, resulting in Un higher than Ulog. Thus, under higher wind conditions, Un - Ulog can contribute up to half the retrieval error (5 of the wind speed magnitude) to the satellite validation exercise.

Item Type: Article
Additional Information: Copyright of this article belongs to Springer.
Uncontrolled Keywords: air temperature; comparative study; relative humidity; roughness; sea surface temperature; wind velocity, Atlantic Ocean; Indian Ocean; Indian Ocean (North); Pacific Ocean
Subjects: Meteorology and Climatology
Depositing User: IITM Library
Date Deposited: 10 Jun 2014 07:14
Last Modified: 10 Jun 2014 07:14
URI: http://moeseprints.incois.gov.in/id/eprint/408

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