[AAS14-10] An Understanding of the Physical Mechanism for the back-to-back Drought over India in last one Century
キーワード：Indian Summer Monsoon, Drought, EL-Nino, LLJ
This work usage the observational and reanalysis data to investigate the primary physical mechanism behind the back-to-back Indian summer monsoon droughts over India. There have been only four back-to-back droughts (e.g., 1904-1905, 1965-1966, 1986-1987, and 2014-2015) over India in the past 120 years. Our analysis have revealed that each of four back-to-back droughts have faced at least one strong El-Nino associated with them, the stronger among the back-to-back drought pair is always associated with the mature phase of EL-Nino. The low-level-jet (LLJ) and the cross-equatorial flow have been reported to be weaker in all back-to-back drought years, except in one drought during 2014. In the majority of back-to-back droughts, the monsoon dynamic features such as the LLJ, cross-equatorial flow, Hadley circulation, and sub-tropical westerly jet are unfavorable for the good monsoon. Overall, the persistent nature of El-Nino condition are found responsible for the two of the back-to-back droughts (1904-1905 and 2014-2015), and partially responsible for the other two back-to-back droughts (1965-1966 and 1986-1987).