Secular variations of surface temperature and precipitation patterns over the great lakes region

Spatial patterns of surface temperature and precipitation variability over the Great Lakes region and their changes during the past 78 years are examined using eigenvector analysis. The results show that the region is homogeneous in terms of temperature variations. The most important regional temperature trends have been very similar to the trends in the average annual temperature for the Northern Hemisphere. In the case of precipitation, however, an important boundary divides the region into a north‐western and south‐eastern portion. Positive precipitation anomalies occurred over the south‐east during the early part of this century and again after about 1960. The north‐western portion, on the other hand, experienced wet conditions during most of the intervening years.