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.
Similar content being viewed by others
References
Blackman R B and Tukey J W 1958 The measurement of power spectra. (New York: Dover Publications)
Krishnamurty T N and Bhalme H N 1976 Oscillations of a monsoon system. Part I: Observational aspects;J. Atmos. Sci. 33 1937–1954
MacDonald G J 1989 Spectral analysis of time series generated by nonlinear processes;Rev. Geophys. 27 449–469
Paul D K and Sikka D R 1976 Extended range forecasting — categorization of weather charts, Part I: Monsoon sea level pressure field. Project report no: ERF/1, 34 pp. (Indian Institute of Tropical Meteorology, Pune)
Press W H, Flannery B P, Teukolsky S A and Vetterling W T 1986 Numerical Recipes. (Cambridge University Press)
Rao Y P 1976 The southwest monsoon. (India Meteorological Department)
Sikka D R and Gadgil S 1980 On the maximum cloud zone and the ITCZ over Indian longitudes during the southwest monsoon;Mon, Weather Rev. 108 1840–1853
Sikka D R and Narasimha R 1995 Genesis of the monsoon trough boundary layer experiment (MONTBLEX);Proc. Indian Acad. Sci. (Earth Planet. Sci.)104 157–187
Srinivasan V and Ramakrishnan A R 1970 Location of the monsoon trough over India in the lower troposphere during July–August. Proc. Symp. Tropical Meteorology;Am. Meteorol. Soc. 2–11 (University of Hawaii, Honolulu)
Srivastav S K 1995 Synoptic meteorological observations and weather conditions during MONTBLEX-90;Proc. Indian Acad. Sci. (Earth Planet. Sci.)105 189–220
Tukey J W 1950 The sampling theory of power spectrum estimates. Symposium onApplications of autocorrelation analysis to physical problems; U.S. Office of Naval Research NAVEXOS-P-735 pp. 47–67 (Washington D.C.)
WMO 1966 Some methods in climatological analysis;WMO Tech. Note No. 81 53 pp. WMO (Geneva)
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Rajkumar, G., Narasimha, R. Statistical analysis of the position of the monsoon trough. Proc. Indian Acad. Sci. (Earth Planet Sci.) 105, 343–355 (1996). https://doi.org/10.1007/BF02841887
Issue Date:
DOI: https://doi.org/10.1007/BF02841887