Novel “flash-cold” metric unveils China's December 2023 weather whiplash
In December 2023, a severe cold wave hit China, marking a striking phase of a "weather whiplash" event-where temperatures flip dramatically between extreme warmth and cold.
"Traditional methods struggle to capture the details of such rapid changes," said CHEN Huayu, a master programme student at the Institute of Atmospheric Physics, Chinese Academy of Sciences. To address this, Chen and collaborators developed the "flash-cold" metric, a novel index to identify and capture sharp, sudden drops in surface air temperature.
Using this metric, they broke down the December event into four distinct stages: warm, first flash-cold, warm again, and second flash-cold. Backward tracing of air parcel trajectories shows that high-latitude atmospheric blocking systems caused both flash-cold phases by directing cold air southward.
"The blocking systems in December developed against a climate backdrop marked by the weakest meridional potential vorticity gradient recorded since 1979," noted Prof. LIU Yimin, the study's corresponding author. "I hope our study could provide a fresh perspective on weather whiplash events and their connection to a changing climate, offering valuable insights to enhance prediction and projection for similar occurrences in the future."