Extended Impact of Cold Air Invasions in East Asia in Response to a Warm South China Sea and Philippine Sea

During boreal winter, the invasion of cold air can lead to remarkable temperature drops in East Asia which can result in serious socioeconomic impacts. Here, we find that the intensity of strong synoptic cold days in the East China Sea and Indochina Peninsula are increasing. The enhanced synoptic cold days in these two regions are attributed to surface warming over the South China Sea and Philippine Sea (SCSPS). The oceanic forcing of the SCSPS on the synoptic cold days in the two regions is verified by numerical simulation. The warming of the SCSPS enhances the baroclinicity, which intensifies meridional wind and cold advection on synoptic timescales. This leads to a more extended region that is subject to the influence of cold invasion.