Impact of abrupt land cover changes by savanna fire on northern Australian climate

Abstract

Dry season fires are probably the largest natural and anthropogenic disturbance in the Australian tropical savannas. A large fraction of this biome is burned annually. The changed surface properties immediately following a fire and during the regrowth period can lead to a significant modification of the surface‐atmosphere coupling. A fire/regrowth scheme has been developed for the Conformal‐Cubic Atmospheric Model. In a highly constrained setup, it uses forcing perturbations that describe the key impacts of a fire as well as the changes of the parameters controlling a vegetation regrowth function in the soil‐canopy model. In good qualitative agreement with observations, the fires lead to abrupt changes in the surface radiation and energy balances. The boundary layer changes lead subsequently to a regionally significantly stronger convection and an intensification of the cyclonic circulation in the area of the Pilbara heat low. There is an enhanced moisture flux into the lower troposphere that helps to increase precipitation. Given a temporal overlap of the regrowth period and the monsoonal wet season, there is a significant influence on the simulated precipitation associated with the Australian summer monsoon. This is a first step of a sensitivity study on the responses of the simulated earth‐atmosphere system over northern Australia at various scales to the impact of temporary land surface changes induced by savanna fire.