Effects of ozone-vegetation interactions on meteorology and air quality in China using a two-way coupled land-atmosphere model

Abstract

Tropospheric ozone (O3) is one of the most important air pollutants in China and is projected to continue to increase in the near future. O3 and vegetation closely interact with each other and such interactions may not only affect plant physiology (e.g., stomatal conductance and photosynthesis) but also influence the overlying meteorology and air quality through modifying leaf stomatal behaviors. Previous studies have highlighted China as a hotspot in terms of O3 pollution and O3 damage to vegetation. Yet, few studies have investigated the effects of O3-vegetation interactions on meteorology and air quality in China, especially in the light of recent severe O3 pollution. In this study, a two-way coupled land-atmosphere model was applied to simulate O3 damage to vegetation and the subsequent effects on meteorology and air quality in China. Our results reveal that O3 causes up to 16g% enhancement in stomatal resistance, whereby large increases are found in the Henan, Hebei, and Shandong provinces. O3 damage causes more than 0.6gμmolgCO2gm-2gs-1 reductions in photosynthesis rate and at least 0.4 and 0.8gggCgm-2gd-1 decreases in leaf area index (LAI) and gross primary production (GPP), respectively, and hotspot areas appear in the northeastern and southern China. The associated reduction in transpiration causes a 5-30gWgm-2 decrease (increase) in latent heat (sensible heat) flux, which induces a 3g% reduction in surface relative humidity, 0.2-0.8gK increase in surface air temperature, and 40-120gm increase in boundary-layer height in China. We also found that the meteorological changes further induce a 2-6gppb increase in O3 concentration in northern and south-central China mainly due to enhanced isoprene emission following increased air temperature, demonstrating that O3-vegetation interactions can lead to strong positive feedback that can amplify O3 pollution in China. Our findings emphasize the importance of considering the effects of O3 damage and O3-vegetation interactions in air quality simulations, with ramifications for both air quality and forest management.