Changes in the factors controlling Northeast Asian spring surface air temperature in the past 60 years

Exploring the predictability sources of Northeast Asian spring surface air temperature (NEAST) is of great socioeconomic importance. In the present study, three factors that alternately take control of NEAST during different epochs in the past 60 years are identified. Specifically, NEAST was found to be closely associated with the Arctic Oscillation (AO) in 1961-1994 (E1), the rainfall over the tropical Indian Ocean (RIO) in 1995-2004 (E2), and the tripole pattern of North Atlantic sea surface temperature (NAT) in 2005-2020 (E3). During E1, zonally elongated barotropic cyclonic anomalies associated with the negative phase of the AO led to negative NEAST. During E2, negative diabatic heating related to suppressed RIO stimulated a Rossby wave train propagating from the Arabian Sea to Northeast Asia, resulting in barotropic cyclonic anomalies in the region and negative NEAST. During E3, positive diabatic heating anomalies in the extratropical North Atlantic induced by NAT caused two quasi-barotropic Rossby wave trains over the mid-to-high latitudes of continental Eurasia. The Rossby wave trains both ended with a barotropic cyclonic anomaly over Northeast Asia, leading to negative NEAST. Further analyses show that the rapid decline in Arctic sea-ice cover in the Sea of Okhotsk and Bering Sea in the mid-1990s, weakening of the central Asian westerly jet, and enhancement of NAT-related rainfall anomalies around the mid-2000s, were responsible for the changes in the factors controlling NEAST. A physical-based empirical model constructed using the three identified factors and their precursors nicely reproduced and forecasted the variation in NEAST, outperforming the hindcast of the coupled dynamical models.

Automated summary

Exploring the predictability sources of Northeast Asian spring surface air temperature (NEAST) is of great socioeconomic importance. This study identified three factors that alternately control NEAST during different epochs in the past 60 years and explained the underlying physical mechanisms. Further analyses revealed the impacts of declining Arctic sea-ice cover, weakening central Asian westerly jet, and North Atlantic rainfall anomalies on the controlling factors. A physical-based empirical model constructed using these factors showed superior performance in reproducing and predicting NEAST compared to coupled dynamical models.