Estimation of vertical diffusivity at the base of mixed layer in the Bay of Bengal
Ashin Kuriakose*, M. S. Girishkumar, M. J. McPhaden, B. Praveenkumar, Pattabhi Rama Rao E
Indian National Centre for Ocean Information Services (INCOIS)
Indian National Centre for Ocean Information Services (INCOIS), Hyderabad500 05 Hyderabad, Telangana, India Pincode: 500090 Mobile: 9995256473 E-mail: email@example.com
Vertical turbulent mixing induced diapycnal heat flux at the base of the mixed layer is an important process that influences the evolution of sea surface temperature (SST). Direct measurements of ocean turbulence require specialized instrumentation and are collected relatively infrequently. An alternative approach to estimating vertical temperature diffusivity (KT ) is to compute it from the residual of the mixed layer (ML) heat budget. Using this approach, we use moored buoy data at 15°N, 12°N, and 8°N along 90°E to estimate the seasonal average of KT at the base of mixed layer in the Bay of Bengal (BoB). We find that KT is lower during spring and higher during winter in comparison with summer and fall at respective mooring locations. Moreover, in a particular season, KT values are relatively high in the southern BoB in comparison to the northern BoB. The present study also shows that the seasonal and spatial variability of KT is modulated both by stratification at the base of ML and through seasonal and spatial heterogeneity in atmospheric forcing fields, most notably wind stress and buoyancy flux. The availability of information on the spatial and seasonal variability of KT in the BoB will facilitate evaluation and validation of turbulent mixing parameterization schemes incorporated into ocean models.