Trend analysis of Atmospheric and Oceanic variables and their compound effect on Tropical Cyclones in the Arabian Sea

The study of atmospheric and oceanic variables is important for understanding the changing patterns and drivers of the large-scale environmental circulation. In the present study, we analyze the annual trend and time series of the Ocean Heat Content (OHC) for the depth of the mixed layer and the maximum thermocline and key atmospheric and oceanic variables controlling the interannual variability of their compound effect on the Genesis Potential Index (GPI) and Potential Intensity (PI) of Tropical Cyclones (TCs). The dataset used for the present study is the ERA5 (ECMWF reanalysis fifth generation) for the atmospheric variables at the spatial resolution of 0.25 grid size monthly data at the surface for 2D and at pressure levels for the 3D and the output of HYCOM (Hybrid Coordinate Ocean Model) with the CFSR (Climate Forcing and System Reanalysis 2) surface forcing and monthly climatology for the lateral boundary forcing at the open boundary for the period 2005–2020. The model output has a resolution of 0.08 and a daily temporal resolution. This study concludes that the OHC of the mixed layer (MLD) and thermocline (MTD) exhibit inverse interannual trends: OHCMLD and OHCMTD increase, and OHCMTD increases at a higher rate, which is significant at the 95% level. The GPI and PI have significant spatial variation. The east-south region of AS, extending to 57 °E in longitude and 12 °N in latitude, is evolving as a region favorable to cyclogenesis, while the north-west, beyond 12 °N to 22 °N and 65 °E, is evolving as a region with diminished cyclogenesis.