Monday 22 August 2005

P1

PM0059
Role of vertical mixing and wind forcing in simulating mixed layer variability of the North Indian Ocean in an OGCM
Devasena, Chikka Kalyani¹, Ramesh, K.V Ramesh¹, Swathi, P.S Swathi¹
1 C-MMACS (Centre For Mathematical Modeling And Computer Simulation), India
Author email: kalyani@cmmacs.ernet.in
The large-scale dynamics of the ocean and the atmosphere are closely related through air-sea interactions on different time scales. The exchange of momentum, heat and freshwater fluxes between the ocean and the atmosphere leads to variabilites in the upper ocean. In turn, energy from the ocean is fedback to atmosphere affecting the tropical atmospheric circulation, the weather and the climate. Thus it is important to simulate upper ocean variabilities to a greater magnitude of accuracy inorder to predict both on mesoscale and synoptic scale weather and ocean prediction. Here, we examine model sensitivity and mixed layer processes to different vertical diffusion schemes (PP, KPP vertical mixing schemes) in simulating the mean, seasonal and interannual variability of sea surface temperature and mixed-layer of Northern Indian ocean. The OGCM used is Modular Ocean Model (MOM4). The OGCM is configured to study various dynamical and thermodynamical processes of North Indian Ocean(NIO). The domain of the Indian Ocean Model extends domain is from 20E-170E (including Indonesioan Throughflow),50S-30N in the north-south direction with a horizontal resolution of 1 deg except for 0.33 deg in the 10S-10N belt. We have setup two sets of model experiments: (a) OGCM is forced with daily NCEP wind stress for the period 1990- 2003 (b) daily quickscat winds stresses. In both the experiments model was forced with monthly NCEP-derived heat fluxes. The results show that different wind forcing and mixing schemes can significantly impact in simulating observed mixed layer process of the NIO. This study also focuses seasonal and sub-seasonal variability of upper ocean during 2000-2003. Model simulations match with observed datasets in capturing the mean and seasonal cycle. The model results are compared with observations at the WHOI mooring site (Arabian Sea) for the year 1994-95, and also with other insitu observations of Bay Bengal for the period 2001-2003.

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