Atmospheric Rivers Amplify the Severity of Summer Humid Heatwaves in Northern China

Humid heatwaves (HHWs) pose severe risks to human health, agriculture, and economics, yet the modulation of these events by atmospheric rivers (ARs) remains poorly understood in East Asia. This study investigates the impact of ARs on summertime HHWs across mainland China. Overall, ARs increase the average HHW intensity in mainland China by 13.0%, with pronounced intensifications of 19.6% in Northwest China and 19.3% in Northeast China. Under AR scenarios, the proportions of extreme HHWs in Northwest China and Northeast China show remarkable relative amplifications of 93.9% and 237.9%, respectively. Mechanism analyses reveal a competing interplay between radiative cooling and moisture advection. While AR‐induced cloud cover significantly attenuates surface shortwave radiation and slightly cools the near‐surface air, this effect is overwhelmed by intense moisture transport. The resulting increase in humidity ultimately drives an increase in wet‐bulb temperature. These findings underscore the importance of AR monitoring for forecasting and early warning of extreme HHWs in China.