ESTIMATION OF LAGRANGIAN AND EULERIAN PREDICTABILITY IN THE BAY OF BENGAL

Abstract:

The Nucleus for European Modelling of the Ocean version 3.6 (NEMO3.6) ocean circulation model is configured to run over a regional domain [30E-105E; 20S-30N] in the Indian Ocean. The model uses 50 levels in vertical with highest resolution of 1 m near the surface. The horizontal resolution of the model is taken as at 1/12^o. It is obtained that the model realistically simulates the salinity, temperature and velocity of the region of interest. The ocean stirring and predictability in the Bay of Bengal (BoB) region of the Indian Ocean is quantified with the help of ocean surface currents derived from the model. The Finite Time Lyapunov Exponent (FTLE) is used as the Lagrangian quatifier for this purpose. In addition to this different Eulerian measures such as Strain Rate, Vorticity and Okubo-Weiss parameter are also computed over the same region. The Lagrangian measures are compared with the Eulerian measures. The predictability analysis using the FTLE suggests that the BoB region exhibits significant spatio-temporally variability with the lowest predictability found during October-November months. The highest predictability is observed during May-July. It is argued that the FTLEs may serve as an important tool in suggesting the sea-going oceanographers about the locations over which more observations will be needed to improve predictability of the region.