Indian Journal of Geo-Marine Sciences Vol. 43(7), July 2014, pp. 1230-1235 Ocean - atmosphere interaction during Thane cyclone: A numerical study using WRF K. K. Vinod 1 , M. Soumya 2 , P.Tkalich 1 & P. Vethamony 2* 1 Tropical Marine Science Institute, National University of Singapore 2 CSIR-National Institute of Oceanography, Dona Paula, Goa, India *[E-mail: mony@nio.org] Received 19 September 2013; revised 7 November 2013 Cyclone 'Thane' developed over the southeast Bay of Bengal (BoB) at 88.5° E, 8.5° N during 25 – 31 December 2011. Simulations have been carried out using Weather Research and Forecasting (WRF) model to generate fine resolution winds that prevailed over the BoB during this extreme weather event. Global Final analysis data from the National Centres for Environmental Prediction (NCEP) having a spatial resolution of 1° and a temporal resolution of 6 h have been used to provide the initial and boundary conditions. The model results (spatial resolution of 12 km and temporal resolution of 1 h) have been validated with track data and vertical observations. Maximum sustained wind speed during Thane cyclone was 15 m/s, and made landfall over Tamil Nadu coast. This study investigates the factors which reinforce cyclone genesis, its propagation and atmospheric parameters that prevailed while the cyclone was passing through the coastal region. We have also studied the variations in sea level along the west coast of India during the passage of Cyclone Thane in the Bay of Bengal and east coast of India. [Keywords: Cyclone Thane, WRF model, Atmospheric parameters] Introduction Cyclone is a natural disaster, which generates serious threats to the coastal environment by strong winds and wind induced storm surges. Tropical oceans are hearts for cyclones (10ºS to 15ºN) 1 . Globally, about 80% of all the tropical cyclones form near to or within the Intertropical Convergence zone (ITCZ) 2 . In this region, unstable flow is generated by latent heat release in deep cumulus convection. ITCZ generates cyclonic potential vorticity anomaly, which reverses the meridonal potential vorticity gradient on its poleward side and it satisfies the necessary condition for the combined barotropic and baroclinic instabilities 3 in lower troposphere. In northern Indian Ocean, the cyclone generation occurs mainly between April and December 4 . Several cyclonic response studies were carried out over northern Indian Ocean by 2, 5-14 . A very severe cyclonic storm ‘Thane’ developed over the Bay of Bengal, crossed the Tamil Nadu coast, close to south of Cuddalore between 0100 and 0200 UTC of 30 December, 2011 with a wind speed of 35 m/s. After the land fall, the system rapidly weakened into a severe cyclonic storm over north Tamil Nadu and into a deep depression over north interior Tamil Nadu. On 31 December 2011, it weakened into a low pressure area over north Kerala. Storm surge of about 1m height inundated the low lying coastal areas of Tamil Nadu at the time of landfall of cyclone 15 . In order to estimate the surge heights and its impact on coastal areas, it is important to determine the cyclone parameters. The objective of present study is to look into the role of various ocean atmosphere parameters and their spatial distribution. In the present study, we examine various cyclone genesis parameters and impact of cyclone on sea surface elevation. Materials and Methods Numerical simulations were carried out to generate the atmospheric parameters over the BoB using the Weather Research and Forecasting (WRF) model 16 . It is based on fully compressible, non-hydrostatic Euler equations, third order Runge-Kutta (RK3) integration scheme and Arakawa C grid. Vertical mixing and diffusion was done by Asymmetric Convective Model with non-local upward mixing and local downward mixing (ACM2) scheme 17 and surface physics by Pleim-Xiu scheme. The global Final analysis data from the National Centre for Environmental Prediction (NCEP) having a spatial resolution of 1° and a temporal resolution of 6 h have been used to provide the initial and boundary