Consistent with earlier studies, this analysis reveals that net surface heat flux primarily controls the ML heat balance. The penetrative component of shortwave radiation plays a crucial role in the ML heat budget in the BoB, especially during the spring warming phase when the ML is thin. During winter and summer, vertical processes contribute significantly to the ML heat budget. During winter, the presence of a strong barrier layer and a temperature inversion (warmer water below the ML) leads to warming of the ML by entrainment of warm subsurface water into the ML. During summer, the barrier layer is relatively weak, and the ML is warmer than the underlying water (i.e., no temperature inversion); hence, the entrainment cools the mixed layer. The contribution of horizontal advection to the ML heat budget is greatest during winter when it serves to warm the upper ocean. In general, the residual term in the ML heat budget equation is quite large during the ML cooling phase compared to the warming phase when the contribution from vertical heat flux is small.

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ABSTRACT:We discuss a method to obtain the spatial estimates of rainfall on the Indian west coast for calculating the surface water budget. The region includes the basin of the Mandovi River, a typical west-coast river whose catchment area includes the Sahyadris range. The rainfall maps obtained by a multivariate interpolation scheme, with elevation as the third variable, were able to capture the sharp increase in rainfall on the windward slopes and the exponential decay in rainfall on the leeward side. The rainfall maps were used to force a hydrological model and the simulated discharge was within 16% of the observed discharge in 16 of 18 years during 1981-1998; the average error over the 18 years was 8%, which is much less than the estimated error of ∼15-20% in the observed discharge. The Mandovi river discharge provided a reliable and independent validation of the accuracy of the rainfall estimate as the river is purely rain-fed. The method provides a better estimate of rainfall in the Mandovi basin, and therefore for the Indian west coast, than existing rainfall datasets. The key result is that treating the windward and leeward sides separately by an a priori, subjective extraction of the ridge line can reduce the underestimation of rainfall that is common in mountainous terrain when the data coverage is sparse.

The longer persistence of the high water level around high tide implies that a storm surge is more likely to coincide with the high tide, leading to a greater chance of destruction. Since the stands are associated with an amplification of the 4-hourly and 6-hourly constituents, storm surges that have a similar period are also likely to amplify more during their passage through the SES.

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