Climatic analysis of tropopause during the northwestern Indian Ocean tropical cyclones

•Increase of TC intensity/frequency over the NWIO, recently.•The largest correlation between the AMO and large-scale dynamical/thermo-dynamical controlling factors affecting TC development.•Decreasing trend of stratospheric temperature over the inner-core and environmental regions of NWIO TCs in the period 1990-2019, and increase of tropospheric temperature over the inner core in this period.•Consistency between the trends of upper-level temperature obtained using ERA5 data and most of CMIP5 GCMs (both historical and RCP8.5 experiments) over the NWIO, as well as for the geopotentical height trends. In this research, tropopause temperature (TT) and tropopause geopotential height (TGH) over the inner-core and environmental regions of all tropical cyclones (TCs) over the northwest of the Indian Ocean (NWIO) from 1990 to 2019 were investigated. To this aim, observational/analysis/reanalysis data and also simulated data from both historical and Representative Concentration Pathway 8.5 (RCP8.5) experiments of some global climate models (GCMs) from the Coupled Model Intercomparision Project (CMIP5) were used. Dynamical and thermo-dynamical environmental factors controlling TC, together with their correlation with different phases of some climatic indices were considered. Results indicated that the eastern part of the NWIO was more favorable for TC genesis and intensification. Lower-level stratospheric (upper-level tropospheric) cooling (warming) was detected over the NWIO during 1990−2019. Over the both inner-core and environmental regions of the NWIO TCs, the coldest tropopause occurred at a CS-Category and the warmest tropopause happened at the first stage of a VSCS event. Over the inner-core (environmental) region, the highest tropopause was detected at the first stage of a CS event (at the end of a VSCS life cycle). A significant majority of the used CMIP5 GCMs produced stratospheric cooling and tropospheric warming trends over the NWIO, similar to those obtained using ERA5 reanalysis dataset. Finally, the decreasing trend of TT over the both inner-core and environmental regions of NWIO TCs together with temperature decreasing trend obtained from the CMIP5 GCMs simulations suggest that the NWIO is prone to experience more TCs, especially the intense ones, in the future.