Climate adjustments over the African-Indian monsoon regions accompanying Mediterranean Sea thermal variability

摘要

This paper analyzes the atmospheric and rainfall anomaly patterns in the African-Indian monsoon region concomitant of warm/cold anomalies confined in the Mediterranean Sea in northern summer. It examines first the similarities and contrasts observed in longitudes, then discusses the results obtained regarding the normal in terms of climate impacts in the Sahelian belt. Statistical results show an opposite African-Indian relationship with stronger (weaker) African (Indian) tropical circulations occurring in warmer (colder) Mediterranean situations and favoring significant increases (decreases) in monsoon circulation, atmospheric moisture content, and deep convection, mainly over the central-eastern Sahel. Model results show that several observed key features can be reproduced through 23 warm/cold anomalies prescribed in the Mediterranean and that warm (cold) situations have an impact on 24 more over the African (Indian) region. Warm experiments generate rainfall excesses in the Sahel with a significant strengthening of southwesterlies. Cold experiments simulate rainfall deficits in the Sahel, associated with an attenuation of southwesterlies in low levels and a zonal moisture transport shifted southward in midlevels. Over India these simulations tend to generate rainfall surplus.