Spherical Harmonic analysis of the normal constant pressure charts in the northern hemisphere

It is believed that the large scale anomalies in the performance of the Indian summer monsoon are a part of the general circulation anomalies having periods larger than the four monsoon months. It may, therefore, be possible to link anomalies of the Indian summer monsoon with anomalies of the global flow pattern, a few months ahead. To get anomalies of global flow pattern, we need quantitative measures of normal global flow pattern. With this idea in view, the monthly northern hemispheric constant pressure charts prepared by Free University of Berlin have been subjected to spherical harmonic analysis form=0, 1, 2,..., 18 andn−m=0, 2, 4,..., 18. The features of normal contour patterns for the months of March to July are pesented in this report form=1, 2 andn−m=0,2 for standard isobaric levels 850, 700, 500, 300, 200 and 100mb. The veritcal and the horizontal tilts of wave numbers 1 and 2 are discussed in some detai