The Maritime Continent Thunderstorm Experiment (MCTEX): Overview and some results

A description is given of the Maritime Continent Thunderstorm Experiment he ld over the Tiwi Islands (12 degrees S, 130 degrees E) during the period No vember-December 1995. The unique nature of regularly occurring storms over these islands enabled a study principally aimed at investigating the life c ycle of island-initiated mesoscale convective systems within the Maritime C ontinent. The program objectives are first outlined and then selected resul ts 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 a s they pass over the heated island. Particular emphasis is given to summari zing the environmental characteristics and the impact this has on the locat ion of storm development and the associated rainfall distribution. The mean rainfall production from these storms is shown to be about 760 x 1 0(5) m(3), with considerable variability. The mesoscale evolution is summar ized and during the rapid development phase the interaction of storms with preexisting convergence zones is highlighted. In situ microphysical observa tions show the occurrence of very large rain drops (up to 8-mm diameter) an d very large concentrations of ice crystals in the -10 degrees to -60 degre es C temperature range associated with the very intense updrafts. Occurrenc e of graupel aloft is shown to be strongly linked to cloud to ground lightn ing. Polarimetric radar-based rainfall estimates using specific differentia l phase shift are shown to be considerably better than reflectivity based e stimates. Studies relating to the structure of anvil cloud and the effect o n the radiative heating profile are also summarized. Initial attempts at mo deling storm development are also presented. Two different nonhydrostatic m odels on days with markedly different evolution are employed and indicate t hat the models show considerable promise in their ability to develop mesosc ale systems. However, important differences still remain between observed s torm evolution and that modeled.