Observed variability in the thermal response of the upper North central Arabian Sea to the forcing of onset Vortex during summer monsoon experiments

Temperature data collected in the upper layers of the central Arabian Sea before and after the onset of the summer monsoon during the three monsoon experiments ISMEX-73 (1973), MONSOON-77 (1977) and MONEX-79 (1979) from stationary ships are made use of to document the observed variability in the upper ocean thermal structure with the onset of the monsoon. Cooling and deepening of the mixed layer and warming below the layer were found to be of unequal magnitudes under the influence of onset vortex during these three years.  Similar differences were also noticed in the profiles of vertical thermal gradient. Absence of a secondary maximum in the vertical thermal gradient during 1973 suggests a weak summer monsoonal forcing during 1972, which was viewed as a global drought year. Large differences were noticed in the changes of accumulative heat content between 1973 and 1979 which were good and bad monsoon years respectively.