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Comparative study of different orographic representations with respect to the Indian summer monsoon simulation

Dash, SK and Mohandas, S (2005) Comparative study of different orographic representations with respect to the Indian summer monsoon simulation. Acta Geophysica Polonica, 53 (3). pp. 325-340.

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In spectral General Circulation Models that are now widely used in operational weather forecasting and research, the time dependent atmospheric parameters and orography are represented in the form of double series. In such spectral transform methods, Gibbs oscillations appear due to sharp gradients in terrain height, moisture, and cloud fields. The present paper shows the usefulness of different digital filters in reducing the negative values of orography. The application of filters also reduces the heights of the mountain peaks. This affects the Indian region the most, because of the presence of the Himalayas and the Western Ghats. In this paper, an attempt has been made to represent the orography by a new method, called the Filtered Modified Orography (FMO), in which a two dimensional Lanczos filter has been applied in the spectral domain globally with a subsequent local enhancement of the Himalayas and the Western Ghats. The dual advantages of reduction in negative orography values and enhancement of mountain peaks were achieved. A comparison with the envelope orography, where the mean orography is enhanced globally, shows that the new method is able to reduce some of the errors and disparities associated with the envelope technique while retaining some of the advantages of the barrier effect regionally. Results show reasonably good representation of global winds, geopotential and rainfall in FMO representation in T80 model of the National Centre for Medium Range Weather Forecasting.

Item Type: Article
Additional Information: Copyright of this article belongs to Institute of Geophysics, Polish Academy of Sciences
Uncontrolled Keywords: Computer simulation; Developing countries; Digital filters; Mathematical models; Rain; Spectrum analysis; Wind, Envelope orography; General circulation models; Gibbs phenomenon; India; Indian summer monsoon rainfall, Weather forecasting, monsoon; orographic effect, Asia; Eastern Hemisphere; Eurasia; India; South Asia; World
Subjects: Meteorology and Climatology
Depositing User: Administrator ePrints@MoES
Date Deposited: 07 Jul 2015 09:32
Last Modified: 07 Jul 2015 09:32

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