Influence of Forest Fire Induced Albedo Differences on the Generation ofMesoscale Circulations

摘要

The development of a mesoscale circulation by the thermal contrast between a fireburned area surrounded by untouched vegetation was simulated by the Regional Atmospheric Modeling System (RAMS) in order to show the circulation's ability to generate clouds and precipitation. The simulations used two fires that occurred during the summer of 1988. The first fire was over 400 square kilometers in size, while the second fire was over 100 square kilometers in size. Results of the 8-hour simulations showed that the thermal differences between the first fire burn area and surrounding unburned area generated a well-developed mesoscale circulation with a vertical updraft speed of over 3.5 m s-1. The simulation also developed clouds and precipitation directly above the circulation center. Simulation of the second fire burn area generated a mesoscale circulation with a vertical updraft speed of over 2.5 m s-1. Although the second simulation did develop clouds and some very light precipitation, it could not be directly tied to the mesoscale circulation itself.