Teleconnections between Pacific sea surface temperatures and Canadian prairie wheat yield

Abstract

Relations between Pacific sea surface temperature (SST) and Canadian prairie wheat yield were investigated by correlation and by composites of SST during the nine lowest yield years, and the nine highest yield years. During winter, the SST anomalies (SSTA) in the North Pacific displayed a three-cell pattern of alternating negative–positive–negative–correlation with wheat yield, stretching diagonally from the Gulf of Alaska to the Philippine Sea. Major asymmetry between the SSTA composites for low yield years and those for high yield years implied a nonlinear relation between SSTA and wheat yield. 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 Niña conditions in the equatorial region having a much more significant influence on Canadian wheat yield than El Niño conditions. A new teleconnection index was constructed from normalized SSTA. For March, this index had a correlation of 0.63 (and a Spearman rank correlation of 0.43) with the wheat yield during 1960–1997.