Teleconnections between Pacific sea surface temperatures and Canadian prairie wheat yield

Relations between Pacific sea surface temperature (SST) and Canadian prairi e wheat yield were investigated by correlation and by composites of SST dur ing the nine lowest yield years, and the nine highest yield years. During w inter, the SST anomalies (SSTA) in the North Pacific displayed a three-cell pattern of alternating negative-positive-negative-correlation with wheat y ield, stretching diagonally from the Gulf of Alaska to the Philippine Sea. Major asymmetry between the SSTA composites for low yield years and those f or high yield years implied a nonlinear relation between SSTA and wheat yie ld. As the composites for low yield years displayed much stronger SSTA than those for the high yield years, low yields seem more predictable than high yields. The composites also showed La Nina conditions in the equatorial re gion having a much more significant influence on Canadian wheat yield than El Nino conditions. A new teleconnection index was constructed from normali zed SSTA. For March, this index had a correlation of 0.63 (and a Spearman r ank correlation of 0.43) with the wheat yield during 1960-1997, (C) 1999 El sevier Science B.V. All rights reserved.