ACCESS-AE: a national, km-scale numerical weather prediction ensemble system
Shaun Cooper
The Bureau of Meteorology is developing a km-scale numerical weather prediction system for a domain that encompasses the entire nation. The system consists of a deterministic model ACCESS-A, and an ensemble system ACCESS-AE that will deliver high-resolution weather information across Australia, including probabilistic predictions of high-impact weather.
ACCESS-A is a 90 vertical level model incorporating convective scale data assimilation with a horizontal grid spacing of 1.5km. ACCESS-AE is a 12-member ensemble with 90 vertical levels and a horizontal grid spacing of 2.2 km. Both use the UK Met Office Unified Model (UM) Regional Atmosphere and Land configuration RAL3.2 and have improved surface characteristics, especially urban areas, via the use of high-resolution datasets to define land cover.
Short trials of ACCESS-AE containing a range of high impact weather case studies have been assessed including tropical cyclones, thunderstorms, frontal systems, fog, fire weather and East Coast Lows. As well as providing an advancement for operational forecasting, ACCESS-AE can also be used as a research tool to better understand atmospheric processes and predictability. For example, ACCESS-AE enables exploration of the atmospheric processes associated with rapid intensification of tropical cyclones by analysing ensemble members, some which capture rapid intensification and others that do not.
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