Onset of the south-west monsoon and sea-surface temperature anomalies in the Arabian Sea

Abstract

In 1979, the year of the Global Weather Experiment, the atmosphere and ocean of the monsoon region were particularly well observed. For this reason, the onset period of the monsoon, 11–19 June 1979, was selected for international comparison of numerical prediction models¹. Previous studies^2–4 have demonstrated that successful predictions for this period are difficult to achieve. I report here two examples of numerical predictions that highlight the role of sea-surface temperatures, namely a control forecast using climatological sea-surface temperatures and an anomaly forecast using more realistic (and warmer) surface temperatures specified for the eastern Arabian Sea. It is shown that the use of the more accurate sea-surface temperatures enables a better prediction of the development of a monsoon depression to be obtained.