Scientists have identified distinct remote atmospheric signals in the Northern Hemisphere that precede the development of an intense Siberian High (SH) and have revealed differing impacts of these signals on the meteorological parameters over East Asia. Understanding these remote signals and their diverse effects is crucial for improving the prediction of extreme weather events associated with the SH.

The SH, a dominant weather pattern characterized by high atmospheric pressure over Siberia, can cause severe cold spells, heavy snowfall, and disruptions to ecosystems and human activities in East Asia. By exploring the atmospheric processes leading up to an intense SH, scientists aim to enhance the accuracy of long-range weather forecasts.

The research team examined reanalysis datasets and conducted numerical experiments to unravel the remote atmospheric signals and their influences on East Asian weather. Their findings revealed two distinct atmospheric patterns – the North Atlantic Oscillation (NAO) and the Arctic Oscillation (AO) – as key factors influencing the evolution of the SH.

Before the occurrence of an intense SH, the study identified opposing phases of the NAO and AO: a negative NAO and a positive AO. These remote signals triggered a chain of atmospheric events:

In the North Atlantic region, the negative NAO favored stronger westerlies over the mid-latitudes and enhanced upward motion of air, forming a positive sea level pressure (SLP) anomaly over Central Siberia.

Over Eurasia, the positive AO intensified the surface westerlies and induced southward cold air transport toward East Asia.

The combination of these remote signals and the dynamics over Eurasia shaped the atmospheric circulation pattern that ultimately led to the development of an intense SH.

Furthermore, the researchers discovered contrasting impacts of the remote signals on East Asian weather. While the negative NAO brought warm and wet conditions to Japan and South Korea, the positive AO caused anomalously cold and dry conditions in Northern China. This highlights the complex interactions between remote atmospheric signals and their differential effects on regional climate.

By uncovering these remote atmospheric signals and elucidating their diverse impacts on East Asian weather, the study provides valuable insights for improving seasonal forecasting of extreme weather events associated with the SH. With enhanced prediction capabilities, societies can better prepare for and mitigate the impacts of these events, contributing to resilience and sustainability in the region.