An observational study of tropical cyclone landfall processes in the Australian region

Previous observational and numerical studies on tropical cyclone (TC) landfall processes revealed that convection distribution and internal structure of the TCs could change substantially, and sometimes in systematic ways such as consistent asymmetry in convection distribution, during landfall. Factors that affect landfall processes include contrasts in the surface sensible heat fluxes, moisture fluxes, and surface roughness due to the land-sea boundary. Synoptic systems in the vicinity that change the ambient vertical wind shear can also modify the structures of the landfalling TCs. Most of these previous studies focused on TCs in the North Pacific and Atlantic but very few of them are on TC landfalls in the Australian region where TCs from the South Pacific, South Indian Ocean and those off the coast of the Northern Territory can make landfall. For example, among the 16 TCs making landfall in the Australian region during the 2005/06-2008/09 seasons, 3 of them were on the east coast (including the disastrous Cyclone Larry in 2006), 11 on the west coast and 2 in the northern region. Variability of TC intensity during landfall is large: There are 3 tropical depressions, 8 tropical storms, 2 equivalent Saffir-Simpson scale category-1 cyclones, and 3 category-3 cyclones. Based on satellite and in-situ observations of these TCs, this paper will present results on the characteristics of the physical processes during their landfall including distributions of convection, wind, surface pressure and surface heat fluxes. Besides the dependence of these characteristics on landfall regions, influences from topography and other synoptic systems have also been examined and will be reported at the Conference.