The microphysical processes in both the melting layer and the warm-rain region of an oceanic mesoscale convective system observed during the Taiwan Area Mesoscale Experiment (TAMEX) are studied using airborne observations. Two flight cases are used, one flown in the transitional region and the other in the stratiform region. In the melting layer the particle number density decreases by an order of magnitude from the top to the bottom of the layer. This is caused by the sharp increase of particle fall speed as snowflakes melt into rain. The ice water content is higher in the transitional region, thus cooling the environment more efficiently during melting. In the warm-rain region the microphysical process is dominated by coalescence process. Large raindrops are generated and the corresponding median diameter of all raindrops increases by a factor of 2 to 3 from the bottom of the melting layer to the ground level. The breakup process is more efficient in the transitional region. ¿ American Geophysical Union 1990