The structure and evolution of the northern Australian dryline

The dryline is a prominent feature of the northern Australian environment. Recently, Arnup and Reeder (2007) constructed a low-level climatology of the northern Australian dryline from the Australian Bureau of Meteorology’s operational Limited Area Prediction System (LAPS) (Puri et al. 1998) forecasts and automatic weather station (AWS) observations. They suggested that the dryline develops as follows: daytime surface heating produces sea-breeze circulations near the coast and a large inland heat trough that extends east-west along northern Australia. At night, air parcels accelerate toward low pressure, increasing convergence and deformation within the heat trough. This wind field sharpens the moisture gradient across the heat trough into a dryline, especially above the surface. The dryline was found to be strongest in the early hours of the morning during spring, confirming observations taken in the southern gulf region of northern Queensland during the Gulf Line EXperiment (GLEX; Goler et al. 2006; Smith et al. 2006). An especially dramatic nocturnal rearrangement of the circulation has been identified recently as a key feature of the West African monsoon circulation (Parker et al. 2005). Here The structure and evolution of the northern Australian dryline