Effects of solar activity and stratospheric QBO on tropical monsoon rainfall

A study on the influence of solar activity and phases of equatorial quasi-biennial oscillation (QBO) on tropical rainfall over India has been made. The results of the total rainfall I,ver the country indicate that during the period of low solar activity, excess/normal rainfall (frequent fl(,ods) are associated with the westerly phase of QBO and deficient/normal rainfall (frequent droughts) cot responded to the easterly phase. During the period of high solar activity only normal rain is observed when QBO is in its westerly phase. Multiple regression analysis has employed to estimate the summer monsoon rainfall using sunspot number and equatorial zonal wind at 15-20 hPa during January-February as independent parameters. A study on the spatial variability of monsoon rainfall in response to the solar activity and phases of QBO has also been attempted.