Morning Precipitation Peak over the Strait of Malacca under a Calm Condition

This paper describes the formation mechanism of morning maximum in the diurnal cycle of precipitation, at the Strait of Malacca under a calm condition, with a nonhydrostatic mesoscale numerical model and ship-based observational data. The morning precipitation peak at the strait is induced by the convergence of two cold outflows that have been produced by the precipitation systems in the previous evening over Sumatra and the Malay Peninsula. The outflows converge at the Strait of Malacca around midnight; a new precipitation system is thus generated and reaches its peak in the early morning. Sensitivity experiments using the numerical model suggest that the timing and position of the morning precipitation peak are affected by the width of the strait. In the case of the Strait of Malacca, its width favors the formation of the morning precipitation system around the center of the strait, which explains why its diurnal cycle of precipitation can be observed much clearer than those in other coastal areas over the Maritime Continent.