CENTRAL AUSTRALIAN COLD FRONTS

This paper presents an observational study of the structure and behavi or of cold fronts over central Australia during the late dry season, a time of year when the prefrontal convectively well-mixed layer is par ticularly deep. The study is based on the results of the Central Austr alian Fronts Experiments (CAFE) held in 1991. Three fronts were docume nted in unprecedented detail for the Australian region using a greatly enhanced surface-observing network and a boundary layer wind profiler , as well as serial upper-air soundings. Data on the surface energy ba lance were obtained also. A common feature of the fronts observed duri ng CAFE was that they were dry, shallow (similar to 1 km deep), and mo ved into a deep (similar to 4 km) convectively well-mixed boundary lay er. One of them initiated major dust storms across central Australia. A prominent feature of the fronts was the marked diurnal variation of their surface signature as they moved through the network. Noteworthy was the tendency during the night for the initiation in the accompanyi ng trough of undular borelike structures or other nonlinear wave distu rbances that moved ahead of the main airmass change. One well-document ed case illustrates the generation of a southerly morning glory bore w ave in the southern Gulf of Carpentaria region. During the daytime, fr onts over central Australia are difficult to locate from surface data and appear to decelerate and to weaken greatly. Some dynamical aspects of the observations are discussed.