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

Abstract

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 shipbased 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.

Relationship between the direction of diurnal rainfall migration and the ambient wind over the Southern Sumatra Island

“…Some previous studies suggest that cold pool dynamics are important to the redevelopment of rainfall systems over the ocean [Sakurai et al, 2009[Sakurai et al, , 2011Fujita et al, 2010]. Cold pools, however, are associated with intense downdrafts produced in the convective core [Feng et al, 2015].…”

“…The relevant processes reported in previous studies include land breeze convergence [Houze et al, 1981], advection by background wind [Mori et al, 2004;Sakurai et al, 2009Sakurai et al, , 2011, self-replication of convective cells [Sakurai et al, 2009[Sakurai et al, , 2011, convergence of cold outflows produced by rainfall systems [Fujita et al, 2010], and gravity waves triggered by daytime heating of the mixed layer on land [Mapes et al, 2003] or convection on land [Love et al, 2011]. effects of seasonality on the diurnal propagation of precipitation systems.…”

A lightning climatology of the South-West Indian Ocean

“…It is worth noting that the strait of Malacca exhibits the second highest flash density. Fujita et al (2010) suggested that gravity currents generated by precipitation over the eastern and western coastal area of Sumatra and Malay Peninsula can converge and trigger convection over the strait. Teo et al (2011) proposed that the strait of Malacca can be seen as a wave cavity.…”

Numerical Study of the Transport and Convective Mechanisms of Biomass Burning Haze in South-Southeast Asia

“…This deep convective transport can be attributed to a strong orographic effect which occurs as the wind is force-lifted over the slope on the West coast of Malaysia and its mountains deeper inland. As the morning precipitation maximum forms (Fujita et al, 2010) at 18 UTC, a higher concentration PM 10 plume rises to at least 200 hPa over the Strait of Malacca as shown in Fig. 8(b) confirming further the transport of biomass burning emissions to the upper troposphere in the region.…”

“…Hence only the results obtained June along both cross-sections. Fujita et al (2010) described the mechanism by which a morning maximum in the diurnal precipitation was formed by the convergence of cold outflows from Sumatra and Peninsular Malaysia over the Strait. These outflows are generally produced by precipitation systems from the previous evening and converge over the Strait at around midnight.…”