Differential Synoptic Circulation Forcing of Land and Coastal Heatwaves

Global warming has intensified heatwaves worldwide, yet their dependence on synoptic circulation remains poorly understood. Here, we identify land and coastal heatwaves during 1959–2023 using a Three‐Dimensional Connected Detection Algorithm, and classify their associated circulation patterns through an integrated EOF‐Kmeans method. We find that heatwave types are strongly associated with the position of anticyclones: coastal heatwaves occur when anticyclones are positioned across the boundary between land and ocean, while land heatwaves prevail when anticyclones are centered over continents. Under global warming, synoptic circulation patterns favorable for heatwave formation are amplified, while those suppressing heatwaves are weakened. Temperature decomposition further reveals that adiabatic heating acts positively (negatively) under anticyclonic (cyclonic) circulation, diabatic heating intensifies heatwaves under most patterns, and temperature advection generally suppresses heatwaves due to land‐sea thermal contrast over coastal regions. These findings highlight the essential role of synoptic circulation in shaping regional heatwave behavior and improving heatwave predictability in a warming climate.