INTERANNUAL VARIATIONS OF TROPICAL PRECIPITATION PATTERNS by

Seasonal and annual precipitation anomalies, normalized with respect to the standard deviations are computed for stations between 30*S and 30N. It is established that the annual anomalies are normally distributed. Spatially averaged anomalies are computed for various regions and their representativeness confirmed. Correlations between the annual average normalized anomalies of the various regions are computed. The results show that simultaneous variations of the zonally oriented circulations of the tropical troposphere occur which are in phase with variations of the Southern Oscillation. The concurrent variations of the intensity of the zonal cells account for most of the observed interannual rainfall variations. Interannual variations in the intensity and position of the meridional Hadley cell seem to play only a minor role. Thesis Supervisor: Reginald E. Newell Title: Professor of Meteorology