Mixed layer depth of the north Indian Ocean during May and September

Abstract

Using a one-dimensional model, Mixed Layer Depth (MLD) is simulated for the north Indian Ocean during May and September. The results are verified with the observed values. Surface meteorological and subsurface data were collected from NODC and IDWRs for 1970-1977 period. The model results indicate that its performance in May is somewhat better in the central Arabian Sea and eastern Bay of Bengal. Excess values are simulated in the western Arabian Sea and central equatorial region. The excess values along the western Arabian Sea are due to coastal upwelling which is not accounted for in the model. In September, the model underestimated the MLD over the western Arabian Sea, whereas it highly overestimates off the west coast of India. The eastward transport of colder surface waters from the extreme western Arabian Sea may be responsible for the low simulated values over the western and central Arabian Sea. In this month, excess values are diagnosed over southern Bay of Bengal. This is the region of net heat loss and negative Ekman Pumping Velocity (EPV). Both these forces augment the mixed layer development. In the absence of EPV term in the model, low MLD should have been simulated. In contrast higher values are found. This shows the deviations in MLD are due to relatively higher values of net heat loss