Spatially Distinct Seasonal Patterns and Forcings of the U.S. Warming Hole.

Abstract: We present a novel approach to characterize the spatiotemporal evolution of regional cooling across the eastern United States (commonly called the U.S. warming hole), by defining a spatially explicit boundary around the region of most persistent cooling. The warming hole emerges after a regime shift in 1958 where annual maximum (Tmax) and minimum (Tmin) temperatures decreased by 0.83°C and 0.46°C, respectively. The annual warming hole consists of two distinct seasonal modes, one located in the southeastern United States during winter and spring and the other in the midwestern United States during summer and autumn. A correlation analysis indicates that the seasonal modes differ in causation. Winter temperatures in the warming hole are significantly correlated with the Meridional Circulation Index, North Atlantic Oscillation, and Pacific Decadal Oscillation. However, the variability of ocean‐atmosphere circulation modes is insufficient to explain the summer temperature patterns of the warming hole. [ABSTRACT FROM AUTHOR]