January 13, 2011

expert comments on flooding in Australia

An expert comments on flooding in Australia.

Dr Andy Morse, School of Environmental Sciences, University of Liverpool, said:

“The heavy rainfall being experienced in Australia is related to changes in sea surface temperatures in the Pacific. The semi-regular ‘ENSO’ cycle of warm and cold events in the equatorial Pacific has seen the strongest negative ENSO phase since the mid 1970s. This change in ocean circulation – associated with La Niña – pushes the warm water of the tropical Pacific towards Australia. This leads to the enhancement of the summer seasonal rainfall especially in the tropical and subtropical regions of north-east Australia.

“This latest flooding has followed a very wet September to November period for much of eastern Australia, with the wettest period on record recorded for some regions. So could this have been predicted? The detailed forecast of areas likely to flood cannot be made more than a few days in advance by meteorologists. However, the long-range forecasts have, for the last six months, predicted seasonally very wet conditions in Australia. The key reason these forecasts work, on a regular basis for some parts of the world, is that the ensemble of global model runs that are used at for example, the European Centre for Medium Range Forecasts (ECMWF) are very good at predicting the ENSO cycle up to six months in advance. In many parts of the world, especially the tropics, there is a good but not exact link between the ENSO phase and rainfall anomalies.”