Advances in Geosciences www.adv-geosci.net 1680-7340 1680-7359 6 1st Alexander von Humboldt International Conference 2006 10.5194/adgeo-6-149-2006 http://www.adv-geosci.net/6/149/2006/ http://www.adv-geosci.net/6/149/2006/adgeo-6-149-2006.html http://www.adv-geosci.net/6/149/2006/adgeo-6-149-2006.pdf 149 153 2006-01-30 The impact of El Niño-Southern Oscillation on the Canadian climate A. Shabbar Environment Canada, Toronto, Ontario, M3H 5T4, Canada The quasi-periodic El Niño -Southern Oscillation (ENSO) phenomenon in the tropical Pacific Ocean produces the largest interannual variation in the cold season climate of Canada. The diabatic heating in the eastern tropical Pacific, associated with the warm phase of ENSO (El Niño), triggers Rossby waves which in turn gives rise to the Pacific-North American teleconnection (PNA) over the North American sector. The strongest cell of the PNA pattern lies over western Canada. In most of southern Canada, mean winter temperature distribution is shifted towards warmer values, and precipitation is below normal. The presence of El Niño provides the best opportunity to make skillful long-range winter forecast for Canada. A strong El Niño event, while bringing respite from the otherwise cold winter in Canada, can be expected to cost the Canadian economy two to five billion dollars.