Vegetation-atmosphere feedback during compound heatwave and drought aggravates the ozone pollution in northern Hemisphere

Extreme weather becomes more frequent with global warming. The compound heatwave and drought (CHWD) events can intensify their individual environmental and societal impacts and cause disastrous threats. Abnormally high concentrations of surface ozone (O₃), were usually observed during CHWD worldwide, while vegetation-atmosphere interactions further complicate the response of ozone to CHWD by influencing BVOC emissions and stomatal deposition processes. Using ERA5 data and major heatwave and drought indicators, the trend of heatwave and CHWD in summer in northern hemisphere during 1960-2023 was analyzed. We then used the online regional meteorology-chemistry model (WRF/Chem) to explore the effects of soil wilting point and dry deposition algorithms on the simulated vegetation-atmosphere feedback processes, as well as their impact on ozone pollution under CHWD. Results show that CHWD events have frequently engulfed many parts of the Northern Hemisphere, which is 3−5 times higher than in past decades. Under the influence of CHWD, more ozone pollution may be caused, especially in Europe, with a 35% increase in ozone concentrations during CHWD. The simulation results show that the increase of isoprene emission promoted the formation of ozone in CHWD summer, while the emission of isoprene is inhibited under drought conditions, mainly concentrated in the area with rich vegetation. Although the reduction of isoprene emissions during droughts inhibits ozone production, the ozone concentration of CHWD in summer is still higher, and high temperature plays a leading role. The wilting point from International Food Policy Research Institute (IFPRI) and Wesely-NoahMP dry deposition algorithms can more accurately describe the vegetation-atmosphere feedback process.