An investigation of the influence of the southern annular mode on Indian summer monsoon rainfall

• Published in: Meteorological Applications
• Main Authors: Pal, Jayanti, Chaudhuri, Sutapa, Roychowdhury, Arumita, Basu, Debjani
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2017
• Subjects: sami
• Online Access: http://dx.doi.org/10.1002/met.1614; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fmet.1614; https://rmets.onlinelibrary.wiley.com/doi/pdf/10.1002/met.1614

ABSTRACT : The present research was aimed at identifying the influence of the southern annular mode on the I ndian summer monsoon ( ISM ) by investigating the inter‐annual as well as seasonal variation in the southern annular mode index ( SAMI ) and the ISM rainfall. It is shown that each month of the ISM is influenced by the southern annular mode of different months. The association between the J une SAMI and J uly rainfall was found to be significant as well as important. The investigation was carried out with the NCEP / NCAR reanalysis dataset. The result shows that the monsoon rainfall anomaly is significantly and negatively correlated with the SAMI . The influence of the J une SAMI is estimated with sea surface temperature ( SST ), horizontal wind at 850 hPa pressure level, vertical wind and moisture convergence. The result shows the existence of warm sea surface at 30 ° S during high SAMI years which is surmised to control the cross‐equatorial flow during the ISM . It was also observed that the enhanced southerly flow over the south of I ndia is divided into two parts. The major flow is observed towards the western A rabian S ea, subsequently turning clockwise and moving towards the western part of I ndia through the north A rabian S ea. The result further shows that an intense ascending motion from the equator to 30 ° N along the western coast coincides with the low rainfall region. These conditions may lead to an enhanced divergence zone over the western and northeastern region of India which, in turn, may result in less rainfall over I ndia.