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Wavelet analysis of intermittent turbulent transport in the atmospheric surface layer over a monsoon trough region

Kulkarni, JR and Sadani, LK and Murthy, BS (1999) Wavelet analysis of intermittent turbulent transport in the atmospheric surface layer over a monsoon trough region. Boundary-Layer Meteorology, 90 (2). pp. 217-239. ISSN 1573-1472

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Abstract

The structure of the turbulence in the atmospheric surface layer over a monsoon trough region has been studied using structural analysis based on wavelet transform. The observational site is located at the eastern (wet) end of the monsoon trough region, characterized by high moisture in the atmospheric surface layer. On the average relative humidity varied from 70 to 100 during the experiment. The wind and temperature data, collected at Kharagpur (22°25' N, 87°18' E) at six observational hours of a day in June 1990 during the Monsoon Trough Boundary Layer Experiment (MONTBLEX), have been utilized in the study. The wind and instantaneous momentum flux time series were decomposed into 12 scales using the Haar wavelet transform. The eddies exhibited a large temporal variability generating intermittency in the energy and flux distributions. A criterion based on the isotropy has been suggested for separating the large eddies from the small eddies. At the separation scale the isotropy coefficient drops sharply. It is shown that the intermittency in the small eddies resulted from the spatial variation of energy, and deviation of velocity statistics from the Gaussian distribution known as flatness. The deviation from the -5/3 power law has been attributed to the increased mean values of, (i) the coefficient of variation of energy, and (ii) the flatness factor, in the inertial subrange. The decomposition of the instantaneous momentum flux time series reveals that the major contribution to the total flux arises from the large eddies. The quadrant analysis of the momentum flux shows that ejections and sweeps account for a substantial part of the total flux, and quantifies the relative importance of the various spatial scales that contribute to the transport of momentum.

Item Type: Article
Additional Information: Copyright of this article belongs to Kluwer
Uncontrolled Keywords: monsoon; statistical analysis; turbulent boundary layer; wavelet
Subjects: Meteorology and Climatology
Depositing User: IITM Library
Date Deposited: 06 Mar 2015 06:07
Last Modified: 06 Mar 2015 06:07
URI: http://moeseprints.incois.gov.in/id/eprint/1650

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