Changes in global land monsoon area and total rainfall accumulation over the last half century

Abstract

This study reports the changes of global land monsoon coverage and monsoon rainfall accumulation. We showed that the combination of monsoon area and rainfall intensity change has led to an overall weakening trend of global land monsoon rainfall accumulation during the last 54 years. This decreasing tendency is mainly caused by the North African monsoon and South Asian monsoon, due to the significant decreasing tendencies of both rainfall intensity and monsoon coverage. The long-term changes of the other monsoon subsystems are not significant in the context of regional average. The monsoon area and rainfall accumulation indices are consistent with the rainfall intensity index in revealing both the inter-decadal and interannual variability. The former appears as an interdecadal oscillation with a peak phase through 1970-1980; the latter appears as the North African, North American and Australian monsoons having stronger spectrum power in the LF (3-7yr) band, while the South African, South and East Asia monsoons having greater powers in the QB (2-3yr) band. Copyright 2008 by the American Geophysical Union.