Statistical analysis of the position of the monsoon trough |
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| Authors: | G Rajkumar R Narasimha |
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| Institution: | (1) Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur P.O., 560 064 Bangalore, India;(2) Centre for Atmospheric Sciences, Indian Institute of Science, 560 012 Bangalore |
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| Abstract: | Using surface charts at 0330GMT, the movement of the monsoon trough during the months June to September 1990 at two fixed
longitudes, namely 79°E and 85°E, is studied. The probability distribution of trough position shows that the median, mean
and mode occur at progressively more northern latitudes, especially at 85°E, with a pronounced mode that is close to the northern-most
limit reached by the trough. A spectral analysis of the fluctuating latitudinal position of the trough is carried out using
FFT and the Maximum Entropy Method (MEM). Both methods show significant peaks around 7.5 and 2.6 days, and a less significant
one around 40–50 days. The two peaks at the shorter period are more prominent at the eastern longitude. MEM shows an additional
peak around 15 days. A study of the weather systems that occurred during the season shows them to have a duration around 3
days and an interval between systems of around 9 days, suggesting a possible correlation with the dominant short periods observed
in the spectrum of trough position. |
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| Keywords: | Monsoon trough statistics spectrum MONTBLEX |
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