What caused the cold condition over northeast Asia during April 2020?

Abstract

Abstract Northeast Asia has experienced severe damage to agricultural and marine ecosystems due to the cold condition in April 2020, despite the fourth warmest year in northern Asia on record. Previous studies have indicated that the dipole atmospheric circulation over Siberia and the East Sea (Japan Sea) rendered this cold environment, although the cause of atmospheric circulation affecting the cold condition over northeast Asia remains nebulous. Herein we found that the atmospheric structure was a mixed result of the East Atlantic/Western Russia (EAWR) pattern and blocking. The wave train was originated from the vorticity forcing of northwest/central Russia and propagated from western Europe to the East Sea via the background westerly and northerly winds. Besides, the Siberian blocking days increased ten times in April 2020 than climatology along with the easterly anomaly over Mongolia–northeast China. The blocking occurrence was linked to wavy westerly at the high latitudes. The strong blocking and EAWR pattern led to the robust dipole atmospheric structure with the prevailing northerly flow in April 2020, thereby causing the cold over northeast Asia. Our results provide novel insights into the cause of the cold condition in April over northeast Asia and its impact on the land-ocean ecosystems.