The Maritime Continent Thunderstorm Experiment (MCTEX): Overview and Some Results

A description is given of the Maritime Continent Thunderstorm Experiment held over the Tiwi Islands (12°S, 130°E) during the period November–December 1995. The unique nature of regularly occurring storms over these islands enabled a study principally aimed at investigating the life cycle of island-initiated mesoscale convective systems within the Maritime Continent. The program objectives are first outlined and then selected results from various observationally based and modeling studies are summarized. These storms are shown to depend typically on island-scale forcing although external mesoscale disturbances can result in significant storm activity as they pass over the heated island. Particular emphasis is given to summarizing the environmental characteristics and the impact this has on the location of storm development and the associated rainfall distribution. The mean rainfall production from these storms is shown to be about 760 × 105 m3, with considerable variability. The mesoscale evolution is summarized and during the rapid development phase the interaction of storms with preexisting convergence zones is highlighted. In situ microphysical observations show the occurrence of very large rain drops (up to 8-mm diameter) and very large concentrations of ice crystals in the −10° to −60°C temperature range associated with the very intense updrafts. Occurrence of graupel aloft is shown to be strongly linked to cloud to ground lightning. Polarimetric radar-based rainfall estimates using specific differential phase shift are shown to be considerably better than reflectivity based estimates. Studies relating to the structure of anvil cloud and the effect on the radiative heating profile are also summarized. Initial attempts at modeling storm development are also presented. Two different nonhydrostatic models on days with markedly different evolution are employed and indicate that the models show considerable promise in their ability to develop mesoscale systems. However, important differences still remain between observed storm evolution and that modeled.