Numerical simulation of sea-breeze circulation over the Arabian Sea during the passage of a cyclonic storm OCKHI using a regional atmospheric model COSMO

In the first week of December 2017, the central Arabian sea witnessed the formation of a very severe cyclonic storm 'OCKHI' that passed through the southern landmass of Indian peninsula. The present study takes advantage of the presence of OCKHI close to the western coastline of India for investigating the influence of a large-scale cyclonic storm on the mesoscale sea-breeze circulation over two coastal stations namely, Thiruvananthapuram (TVM) and Cochin (COK). We present numerical simulation of the sea-breeze circulation over these two stations for 16 consecutive days from 24 November to 10 December 2017 through a regional atmospheric model - COSMO. Results obtained from the present study show weakening of the sea-breeze circulation cell during the passage of cyclonic storm, which is attributed to a substantial rise in the coastal-breeze component (CBC) and an associated dip in the sea-breeze component (SBC), resulting in low values of SBC/CBC ratio. After the dissipation of the storm, both the coastal stations showed a prominent sea-breeze circulation cell comprising a sea-breeze flow capped with a counter return flow aloft. In the dissipation phase of the storm, one of the striking features is the clear visibility of return flow which is otherwise difficult to distinguish over these locations during the study period.