Improving model representation of rapid ozone deposition over soil in the central Tibetan Plateau†

Abstract

Ozone soil deposition contributes a major part to the total deposition of ozone on land covered by low vegetation and perturbs the ozone budget on both regional and global scales. Large model-observation divergences in ozone soil deposition require continuous efforts to improve the mechanical understanding and model representation. Observation of ozone deposition over bare soil directly meets the requirement. Here, we performed field observation of ozone deposition over bare soil first available in the Tibetan Plateau (TP) using the aerodynamic gradient method. A top ozone deposition velocity with a daily mean of 0.49 ± 0.11 (1 sd) cm s⁻¹ (1 May to 10 July 2019) and an hourly mean maximum across the diel pattern of 0.73 ± 0.67 cm s⁻¹ in the afternoon were recorded. Such rapid ozone deposition was mainly attributed to extremely low soil resistance (R_soil), which was further regulated by median low soil clay content, dry conditions, and strong solar radiation in the central TP. Parameterization of R_soil in the newly developed Stella scheme was demonstrated to be effective according to our verification. An updated scheme was further attained with the inclusion of our observation and better represents the R_soil variability than the Stella scheme. More verification is therefore encouraged and hopefully to improve the Stella scheme. Finally, both the Stella scheme and our updated scheme showed great advantages over the oversimplified scheme in current models and should be considered more seriously for the sake of better representation of ozone soil deposition and its variability.