The 11th Conference on Applied Climatology

J2.6
TELECONNECTION OF THE 1997 EL NINO OBSERVED BY SPACEBORNE SENSORS AND THE DECADAL ANOMALIES ION THE NORTHEAST PACIFIC

W. Timothy Liu, JPL, Pasadena, CA; and H. Hu and X. Xie

Three regions of simultaneous anomalous warming in the North Pacific Ocean, from Spring to Fall of 1997, are related to wind anomalies through different mechanisms, as observed by the NASA Scatterometer and other spaceborne sensors. The anomalous warming along the equator is part of the developing El Nino and is related to the relaxation of the trade winds, the westerly wind anomalies, and the depression of the ocean thermocline. The anomalous warming along the west coast of the United States develops as a pre-existing pool of warm water moves with a system of anomalous cyclonic wind towards the coast. The warm pool is part of a dipole of sea surface temperature (SST) anomalies that has been present for more than a year in the North Pacific. The dipole is largely maintained by surface heat flux. Winds coming from the tropical ocean bring heat and moisture and suppress evaporative cooling. The associated clouds may also block solar heating. The opposite is true of winds from the north. A persistent cyclonic flow may cause a temperature dipole with warm water in the east and cold water in the west. The anomalous warming along the Mexican coast is caused by suppression of coastal upwelling and the third temperature anomalies. Under normal condition, the northerly winds along the coast associated with the subtropical high pressure system cause offshore Ekman transport and coastal upwelling. The correspondence of the westerly wind anomalies with the cyclonic circulation in the North Pacific and southerly wind anomalies off the American coast suggests wind as the mechanism of teleconnection; wind-forcings of the equatorial and midlatitude thermal anomalies are related. NSCAT also observes intraseasonal variabilities in the western Pacific and Indian Ocean and the extratropical northerly wind surge before the onset of westerly wind anomalies in the central equatorial Pacific. Their roles in triggering westerly wind burst and as precursors of El Nino are being investigated

The 11th Conference on Applied Climatology