Using dynamical downscaling to simulate rainfall for East Coast Low events.
Ji, F., Ekstrom, M. and Evans, J.P.
In Chan, F., Marinova, D. and Anderssen, R.S. (eds) MODSIM2011, 19th International Congress on Modelling and Simulation. Modelling and Simulation Society of Australia and New Zealand, December 2011, pp. 2733-2739. ISBN: 978-0-9872143-1-7.
East Coast Lows (ECLs) are intense low-pressure systems which occur on average several
times each year off the eastern coast of Australia, in particular southern Queensland, New South Wales
(NSW) and eastern Victoria. East Coast Lows will often intensify rapidly overnight making them one of the
more dangerous weather systems to affect and damage the eastern coast of Australia each year. They are also
a major source of water for the reservoirs serving coastal communities and ECL events were identified as
being responsible for most of the high inflow days in the NSW coastal catchments.
In this study, four East Coast Low events, covering the various ECL categories, are simulated using the
Weather Research and Forecasting (WRF) model in order to assess the model’s ability to capture the ECL
events. By choosing various combinations of two Planetary Boundary Layer (PBL) schemes, two Cumulus
(Cu) schemes, three microphysics (mp) schemes and three radiation (ra) schemes, a 36 member multi-physics
ensemble is created and evaluated against observations. The uncertainties among the 36 ensemble members
are analysed, rainfall probability assessment undertaken and the best estimation of the simulated rainfall are
The results suggest that the Betts-Miller-Janjic cumulus scheme and the Yonsei University planetary
boundary layer scheme can be chosen with some robustness to simulate rainfall pattern and the intensity and
position of rainfall centres. Results further indicate that the selection of the cumulus scheme options has the
largest impact on model performance during the more intensive rainfall events.
The conclusions from the study can be applied to better estimate rainfall amount and its distribution from
dynamical downscaling of climate change projections.
Figure 6: The best estimated rainfalls for NEWY (left) and SURFERS (right).
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Last updated 31st January 2013