Life Cycles of Agriculturally-Relevant ENSO Teleconnections in North and South America

Abstract:

Studying ENSO teleconnections as a time-invariant phenomenon is often a useful conceptual framework. However, the seasonal and interannual progression of teleconnections is important for providing useful forecasts. In this study we analyze how climate sensitive portions of major crop growing regions and seasons relate to multi-year ENSO life-cycles in North and South America. We find that temperature and precipitation teleconnections forced directly by sea surface temperature (SST) anomalies during boreal winter lead to soil moisture anomalies that persist through the spring to affect major growing seasons in both North and South America.

Peak SST anomalies in ENSO life-cycles force atmospheric wave trains that lead to strong teleconnections during boreal winter. These teleconnections are concurrent with, and therefore critical for, South American growing seasons but less so for those of North America. Lagged teleconnections are of primary importance in North America, where the growing season often coincides with near-neutral SST anomalies. Major wheat producing regions of North America coincide with areas of significant soil moisture memory, such as the southern Great Plains, in which peak wintertime teleconnections force soil moisture anomalies that can persist through to early spring. Lagged soil moisture teleconnections also play a role in the late winter / early spring growing seasons of South America, particularly in Argentina.