Application of Extended Empirical Orthogonal Function Analysis to Interrelationships and Sequential Evolution of Monsoon Fields

Abstract

Extended empirical orthogonal function (EEOF) analysis has been employed to study linear relationships among the mean sea level pressure, 700 mb height and rainfall over India, and their low-frequency sequential evolution during the peak summer monsoon months. The interrelationships between these fields are strongest over central India and, while the rainfall activity is colocated with the corresponding changes in the 700 mb heights, it is displaced southward with respect to the pressure changes. The first two EEOF's of all the three fields (averaged over 5 or 7 days) show that the dominant low-frequency sequential evolution is associated with north and northeastward movement of the anomaly centers with a recurrence period of about 40 days. In addition, the presence of a westward moving wave in sea level pressure anomalies located roughly near 15°N latitude is revealed by the third EEOF.