Dry Deposition of Ozone Over Land: Processes, Measurement, and Modeling

Dry deposition of ozone is an important sink of ozone in near‐surface air. When dry deposition\r\noccurs through plant stomata, ozone can injure the plant, altering water and carbon cycling and reducing\r\ncrop yields. Quantifying both stomatal and nonstomatal uptake accurately is relevant for understanding\r\nozone's impact on human health as an air pollutant and on climate as a potent short‐lived greenhouse gas\r\nand primary control on the removal of several reactive greenhouse gases and air pollutants. Robust ozone\r\ndry deposition estimates require knowledge of the relative importance of individual deposition pathways,\r\nbut spatiotemporal variability in nonstomatal deposition is poorly understood. Here we integrate\r\nunderstanding of ozone deposition processes by synthesizing research from fields such as atmospheric\r\nchemistry, ecology, and meteorology. We critically review methods for measurements and modeling,\r\nhighlighting the empiricism that underpins modeling and thus the interpretation of observations. Our\r\nunprecedented synthesis of knowledge on deposition pathways, particularly soil and leaf cuticles, reveals\r\nprocess understanding not yet included in widely used models. If coordinated with short‐term field\r\nintensives, laboratory studies, and mechanistic modeling, measurements from a few long‐term sites would\r\nbridge the molecular to ecosystem scales necessary to establish the relative importance of individual\r\ndeposition pathways and the extent to which they vary in space and time. Our recommended approaches\r\nseek to close knowledge gaps that currently limit quantifying the impact of ozone dry deposition on air\r\nquality, ecosystems, and climate.