Decadal Change in Cold Wave Intensity Over China: Cold Air Trajectories and Physical Processes

Abstract Severe cold wave (CW) events have continued to be witnessed in recent decades, raising concerns about their changing characteristic under climate change. This study investigated decadal variability of CWs over China, focusing on intensity changes and thermodynamic processes. While CW frequency declined under global warming, its intensity has significantly increased during 2001–2021 compared with 1977–2000, with a marked cooling center over Inner Mongolia. Using Lagrangian trajectory analysis and clustering, we identified four major cold air pathways, with the common Northeast China–Inner Mongolia cluster contributing most to recent intensification. Although air masses were initially warmer in the later period, they underwent greater net cooling along this cluster. Compared with 1977–2000, median air parcel in 2001–2021 was ∼2.0 K colder during days −5 to −2, due to stronger diabatic (∼1.0 K) and adiabatic (∼0.9 K) cooling. This was compounded by ∼1.9 K weaker warming from days −2 to 0, driven by reduced adiabatic warming (∼0.7 K) and continued diabatic cooling (∼0.7 K). Adiabatic and diabatic processes contributed comparably (∼50%) to the enhanced cooling. Intensified CWs were associated with a stronger and more persistent Ural ridge, which extended into the Arctic, promoting deeper descent and stronger ascent motions. The deeper descent brought air masses downward to higher pressure levels, enabling more diabatic cooling and limiting later adiabatic warming while enhanced ascent increased adiabatic cooling. Additionally, a poleward shift in air trajectories further amplified diabatic cooling efficiency. The findings highlight northward‐shifted cold air pathways and thermodynamic processes that enhance CWs under a warming climate.