Abstract
The importance of resolving mesoscale air-sea interactions to represent
cyclones impacting the East Coast of Australia, the so-called East Coast
Lows (ECLs), is investigated using the Australian Regional Coupled Model
based on NEMO-OASIS-WRF (NOW) at $1/4^\circ$
resolution. The fully coupled model is shown to be capable of
reproducing correctly relevant features such as the seasonality, spatial
distribution and intensity of ECLs while integrating more physical
processes, including air-sea feedbacks over ocean eddies and fronts. The
thermal feedback (TFB) and the current feedback (CFB) are shown to
influence the intensity of tropical ECLs (north of
$30^\circ S$), with the TFB modulating the pre-storm
sea surface temperature and the CFB modulating the wind stress. By fully
uncoupling the atmospheric model of NOW, the intensity of tropical ECLs
is increased due to the absence of the cold wake that provides a
negative feedback to the cyclone. The number of ECLs might also be
affected by the air-sea feedbacks but large interannual variability
hamper significant results with short term simulations. The TFB and CFB
modify the climatology of sea surface temperature (mean and variability)
but no direct link is found between these changes and those noticed in
ECL properties. These results show that the representation of ECLs,
mainly north of $30^\circ S$, depend on how air-sea
feedbacks are simulated, with significant effects associated with
mesoscale eddies. This is particularly important for atmospheric
downscaling of climate projections as small-scale sea surface
temperature interactions and the effects of ocean currents are not
accounted for.