Flash floods are major meteorological disasters which occur around the globe. Understanding of this phenomena is a challenging problem because it is necessary to understand both complex dynamic and microphysical processes at scales of motion that are smaller than typically measured by conventional weather networks. This scale of motion is termed mesoscale by meteorologists. The National Science Council of Taiwan has established a Multiple Hazards Mitigation Project whose meteorological component is focussed on improving flash flood predictions -- especially flooding associated with a meteorological phenomenon known as the Mei-Yu front. A major field project to study the systems that cause flash floods, entitled the Taiwan Area Mesoscale Experiment, was held in the Spring of 1987. The project was cosponsored by the National Science Council with participation of the National Science Foundation and the National Oceanic and Atmospheric Administration of the United States. Under a previous award the Principal Investigator developed and applied a three-dimensional numerical model to the investigation of the characteristics of the Mei-Yu and its interactions with the topography of Taiwan and the synoptic environment. The model was able to accurately simulate and reveal details of the dynamics of flash flood events. The Principal Investigator will continue and expand on his previous research. Specific objectives include investigating: formation of the low-level jet and its interaction with the topography and mesoscale flows; the effects of diabatic heating/cooling on mesoscale circulations near the Mei-Yu; and the interactions between the mesoscale events and the synoptic scale forcing.
