| 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. |