Estimation of drag coefficient over the western desert sector of the Indian summer monsoon trough

Mohanty, U. C. ; Parihar, P. S. ; Venugopal, T. ; Parashuram, (1995) Estimation of drag coefficient over the western desert sector of the Indian summer monsoon trough Proceedings of the Indian Academy of Sciences - Earth and Planetary Sciences, 104 (2). pp. 273-287. ISSN 0253-4126

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In the estimation of momentum fluxes over land surfaces by the bulk aerodynamic method, no unique value of the drag coefficient (C D) is found in the literature. The drag coefficient is generally estimated from special observations at different parts of the world. In this study an attempt is made to estimate drag coefficient over the western desert sector of India using data sets of Monsoon Trough Boundary Layer Experiment (MONTBLEX) during the summer monsoon season of 1990. For this purpose, the fast and slow response data sets obtained simultaneously from a 30 m high micro-meteorological tower at Jodhpur are used. All the observations used in this study are confined to a wind speed regime of 2.5-9.0 ms-1. A comparison of momentum fluxes computed by eddy correlation (direct estimation) with profile and bulk aerodynamic (C D = 3.9 × 10-3, Garratt, 1977) methods revealed that though the nature of variation of the fluxes by all these methods is almost similar, both the indirect methods give an under-estimated value of the fluxes. The drag coefficient is estimated as a function of wind speed and surface stability by a multiple regression approach. An average value of the estimated drag coefficient is found to be of the order of 5.43 × 10-3. The estimated value ofC D is validated with a set of independent observations and found to be quite satisfactory. The recomputed momentum fluxes by bulk aerodynamic method using the estimated drag coefficient are in close agreement with the directly estimated fluxes.

Item Type:Article
Source:Copyright of this article belongs to Indian Academy of Sciences.
Keywords:Drag Coefficient; Momentum Fluxes; Bulk Aerodynamic Method; Eddy Correlation Method
ID Code:26642
Deposited On:08 Dec 2010 13:27
Last Modified:17 May 2016 09:56

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