Investigating the link between Mainland-Indochina monsoon onset dates and cyclones over the Bay of Bengal basin.

This study delves into the intricate connection between Mainland Indochina Southwest Monsoon (MSWM) onset dates and tropical cyclones (TCs) over the Bay of Bengal (BOB) and Arabian Sea (ABMS). Utilizing datasets like International Best Track Archive for Climate Stewardship (IBTrACS), European Centre for Medium-Range Weather Forecasts Reanalysis data version 5 (ERA5), and Climate Hazards Group Infrared Precipitation with Station data (CHIRPS) daily rainfall data, the research highlights the influence of TCs on monsoon onset, emphasizing sea surface temperatures and rainfall intensity. The bimodal distribution of cyclones during early and late onset years is noted, during MSWM onset month May. Significant correlations emerge between cyclone frequency, monsoon onset dates, SST, and rainfall patterns. Employing a robust methodology, the study reveals a complex relationship between TCs and monsoon onset, with late-onset years experiencing higher TC numbers. Additionally, the research explores the influence of El Niño–Southern Oscillation (ENSO), associating positive phases with late monsoon onset and negative phases with early onset and increased rainfall. However, interestingly ENSO has less influence than the TCs over the monsoon onset process. And TCs dynamic may influence cut-out monsoon flow from formal circulation. The findings underscore TCs' multifaceted role in shaping the monsoon, offering insights into intricate climate variables and cyclone dynamics in the northern Indian Ocean. [ABSTRACT FROM AUTHOR]