Variability of surface fields in different branches of monsoon

Abstract

ABSTRACT. Characteristics of the surface fields. such as zonal and meridional components of pseudostress. surface pressure, latent and sensible heat fluxes, sea surface temperature (SST) and air temperature for the years 1985 and 1986, are studied using ECMWF model-analysed data and FSU data obtained from TOGA CD-ROM (1990). Three branches of monsoon. Viz. (i) Arabian Sea; (ii) Bay of Bengal and (iii) South China 1 Sea are observed in pseudostress, surface pressure and latent heat flux. However, the other three surface fieldsdo not reflect the branching phenomenon.

The Arabian Sea and Bay of Bengal branches depict strong signals of variability in the surface fields in association with the monsoon variability compared to the south China Sea branch. Arabian Sea branch is observed to have the strongest signals in the pseudostress and latent heat flux transfer whereas surface pressure is having the lowest value over the Bay of Bengal. Southern Indian Ocean shows significant variability in surface pressure in comparison to the three branches of monsoon. Strong positive radient of pseudostress in association with sudden increase of latent heat flux front May to June, and the pre-monsoonal pressure drop (March to April) in 1985 are the most prominent features associated with better monsoon activity. Inter-annual variability in sea surface temperature (SST) is not well marked but differences in SST amongst the three branches are significant.