Cause of the cold condition over northeast Asia in April 2020

Although northern Asia's temperature was the fourth highest on record, Northeast Asia was severely damaged agricultural and marine products due to the cold condition in April 2020. Previous studies have shown that the dipole atmospheric circulation over Siberia and the East Sea (also referred to as the Japan Sea) rendered this cold environment. Here we show that the atmospheric structure affecting the cold condition over northeast Asia 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 toward the southeast via the climatologically westerly and northerly flows. Furthermore, the blocking days over Siberia increased approximately ten times in April 2020 than climatology along with the easterly anomaly over Mongolia–northeast China. The blocking occurrence might be connected to wavy westerly at the high latitudes. The strong blocking and EAWR pattern led to the robust dipole atmospheric structure with the prevailing northerly wind in April 2020, thereby causing the cold over northeast Asia. Our results help to understand the cause of the cold condition in April over northeast Asia and its impact on the land and ocean ecosystems.