RELATIONS BETWEEN THERMAL INVERSION AND THE DISTRIBUTION OF UPPER LAYER DEPTH, AND THE TROPICAL CYCLONE HEAT POTENTIAL IN THE BAY OF BENGAL

The spatio-temporal variation of the thermal inversion, their formation mechanisms, and their effects on the variation of upper layers depth as well as the tropical cyclone heat potential is examined utilizing the ARGO profiles in the Bay of Bengal. In this basin, the thermal inversion shows significant temporal and spatial variations, which not only exist in winter but also form and sustain throughout the year. Thermal inversion sprout in April-May due to the start of slight precipitation and river discharge, and consequently act as a precursor for formation. It sluggishly increases from summer to autumn mostly nearby the river dominant regions. During the winter, low net heat flux help magnify the inversion and suggest surface cooling is important for their sustenance and amplification. Annual variability of inversion shows an increasing trend that is well-correlated with the decreasing trend of the net heat flux and increasing trend freshwater flux from 2009 to 2013. The originating depth, the depth of peak inversion, and thickness of the inversion layer exhibit a noteworthy positive correlation with the mixed layer depth (MLD), isothermal layer depth (ILD), and barrier layer thickness (BLT) respectively. In the case of strong inversion, starting depth of the barrier layer and the MLD becomes thinner compare to the non-inversion events. Hence, the inversion layer and barrier layer both lying in the bottom part of ILD hamper the vertical mixing, which may reduce the productivity in this bay. Inversions generates more tropical cyclone heat potential than that of non-inversion profiles and thus, exhibit their importance in the intensity of cyclones that needs more clarifications by future studies. More detailed analysis by taking buoy and ship observations with a high-resolution model may help to quantify the role of all external forcing (e.g., freshwater flux, heat flux, wind, air temperature etc.) on the evolution of inversion, and to linkup with their applications in this bay.