The North Atlantic Tends to Amplify the Arctic Stratosphere‐Induced Eurasian Subseasonal Surface Air Temperature Anomalies During the Cold Season

Abstract

Based on atmospheric reanalysis data from 1979 to 2024 during the cold season, this study investigates the evolutionary mechanisms and predictability of the leading EOF mode of the Eurasian subseasonal surface air temperature (SAT). The results indicate that the early‐stage anomalous subseasonal signal appears to be associated with Arctic stratospheric potential vorticity (PV) anomalies and subsequently propagates southeastward toward Eurasia. The tripolar pattern of North Atlantic sea surface Net Turbulent Heat Flux (NTHF) anomalies relates to the secondary enhancement of the geopotential height anomalies over Eurasia by transmitting eastward wave activity flux. This enables the subseasonal signal to propagate downward into the lower‐tropospheric temperature field. To quantify the contribution of each factor, a piecewise potential vorticity inversion method is employed. The analysis indicates that the Arctic stratospheric PV intrusion and the upper‐tropospheric dynamic processes associated with the North Atlantic tripolar NTHF anomalies are the dominant factors regulating geopotential height anomaly during the SAT subseasonal events. In contrast, mid‐tropospheric latent heat release makes no significant contribution, while lower‐tropospheric static stability and baroclinicity even suppress its development. Based on these findings, two predominant predictors are defined: the 8‐day leading Arctic PV index and the 4‐day leading North Atlantic tripolar NTHF index. Using a bivariate linear regression model, the Eurasian cold‐season subseasonal SAT can be preliminary predicted. Validation results show a daily correlation coefficient of 0.41 between the predicted and observed first principal component, providing theoretical support for improving the forecast accuracy of the Eurasian cold‐season subseasonal SAT variability.