Inter-Annual Variability of Southwest Monsoon Rainfall in Myanmar: Insights from Ocean-Atmosphere Interactions

Abstract

Abstract The monsoon trough regions in Myanmar (90°E-105°E and 10°N-28°N) show a substantial influence on rainfall from June to September during the southwest monsoon season (JJAS), where the contributes ~90% of the annual accumulated rainfall. This finding aims to explain the variability of southwest monsoon rain and its connection to Myanmar's ocean-atmosphere pattern between 1981 and 2020, which is of great importance in the economy of Myanmar because JJAS is the summer monsoon cropping season which is the main economic sector. The dominant EOF mode captures the lag-correlated between the average trend of JJAS rainfall and SST for 40 years (1981– 2020) produced from the previous June-September SST correlation with rainfall variation over Myanmar. Furthermore, the correlation suggests the instance of El Niño–Southern Oscillation (ENSO) and IOD (DMI) influence the variability of inter-annually JJAS rainfall. Positive correlation between SST anomalies of Nino3.4 regions and western IO (DMI) with JJAS rainfall variation during this 40 years. Both are well-defined indices for the forecast of the study year’s JJAS rainfall over Myanmar. Furthermore, cooling (warming) across the Indo-Pacific influences the Hadley and Walker circulations, resulting in below (above) average rainfall over Myanmar. The impact of other indices on JJAS Myanmar rainfall requires additional investigation. The thorough examination of JJAS rainfall aids in understanding the occurrences of previous extreme events as support for predicting and monitoring drought and floods over Myanmar.