Toward Realistic Prognostic Modeling of the Methane Chemical Loss
Journal Article
Overview
abstract
Abstract; Global modeling of the hydroxyl radical (OH) remains a significant challenge, pushing chemistry‐climate models to rely on idealized scenarios with methane () concentrations rather than emission fluxes. In this study, we employ an emission‐driven configuration in the Community Earth System Model Version 2.2 (CESM2.2) and demonstrate the effect of incorporating detailed Short‐Lived Halogen (SLH) chemistry representation on both emission‐ and concentration‐driven simulations in terms of global methane loss and overall chemical dynamics. The net impact of the updated SLH chemistry reduces ozone () and hydroxyl radical (OH) in both hemispheres, resulting in higher abundance and longer lifetime of carbon monoxide (CO) and . Comparisons with NASA's Atmospheric Tomography (ATom) mission data show joint improvements in OH, , CO and . Further evaluation against CO measurements from NASA's Measurement of the Pollution in The Troposphere (MOPITT), from JAXA's Greenhouse Gases Observing Satellite (GOSAT) confirms significant amelioration in modeled CO and , especially in the Northern Hemisphere during winter and spring, correcting a common wintertime underestimation. The annual tropospheric loss with OH is reduced from 573 to 504 Tg in 2017, resulting in an increase in lifetime of about 1.2 years, bringing it to approximately 10 years, which is well within the range of uncertainty in empirical estimates. In contrast, the estimated chlorine sink increases from 2 to around 15 Tg . Additionally, we find that the sensitivity of the ’s chemical loss to CO emission changes is underestimated in the prescribed simulations.
