The large-scale meteorological condition during the critical stage of Mesoscale Convective Complexes (MCCs) over Indian Ocean

Abstract

This study analyzed the large-scale meteorological condition during Mesoscale Convective Complexes (MCCs) over the Indian Ocean. The MCCs were identified by infrared satellite imagery using an algorithm that combined information about cloud coverage, eccentricity, and the cloud lifetimes of MCCs. The data used were a combination of satellite data and reanalysis data, while the Brightness temperature (TBB) was obtained from the MTSAT IR1 satellite data. The results of this study showed that, in general, the initial stage of the MCC was characterized by strong low-level convergence and vertical convection, and largely driven by the convergence of the moisture flux in the lower troposphere. The mature stage of the MCC was characterized by weak surface convergence, strong upper-level divergence, and a shortwave ridge in the mid- and upper levels. Where there was strong surface divergence, the decay and dissipation stages were very similar, and the surface convergence left the system. The movement of most MCCs resulted from the combined contributions of advection and the propagation of surface convergence. Results from this research showed that these large convective systems tended to be formed in the vicinity of the terminus of a low-level jet that transported moist and warm air to the originating regions of the MCCs. Shortwave troughs and baroclinic zones were associated with MCC development.