Possible Tidal Modulation of the Indian Monsoon Onset.
AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH
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The a priori hypothesis that soli-lunar atmospheric tides can induce an element of the variability in mean monthly climatic data is tested using precipitation 1985-1960, station pressure 1895-1960 and 300 mb height data 1950-1977 for India during the monsoon onset month of June. Since the monsoon onset occurs, on average, very late in the month in northern India, this region is very sensitive to small departures from normal in the onset date. These departures can be seen in the year to year fluctuations of June rainfall amounts. To test the hypothesis involving lunar atmospheric tides, a time series of mean monthly lunar tidal potential for June 1985-1960 was calculated. The results of this research showed that there is an important periodic component on the order of one standard deviation during hemispherically cold periods in the interannual variability of pressure, precipitation, and upper air winds for the Indian monsoon onset month of June at the two dominant lunar frequencies and that the atmospheric response is in phase with the forcing. This strongly suggests that lunar atmospheric tides to produce an element of the observed interannual variability.