Hydroxyl Radical (OH) Response to Meteorological Forcing and Implication for the Methane Budget
Jian He, Vaishali Naïk, Larry W. Horowitz
Abstract
Abstract The hydroxyl radical (OH) is a powerful oxidant in the troposphere controlling the atmospheric lifetimes of many short‐lived climate forcers such as methane. In this study, the GFDL‐AM4.1 model is used to investigate the meteorological impacts on OH and the methane budget and lifetime over 1980–2017. Driven by meteorological reanalyses from the National Centers for Environmental Prediction and the Modern‐Era Retrospective analysis for Research and Applications (Version 2), our model gives an 11.2 Tg yr −1 difference in the derived methane emissions and 0.24 years difference in the estimated methane lifetime. The results suggest that meteorology affects the mean OH concentrations but not OH trend, while the latter shows strong correlation with reactive nitrogen emissions. Despite the relatively small difference in global tropospheric OH (∼2%) induced by different meteorological forcings, the difference is much larger regionally, leading to a difference of 8 Tg yr −1 in tropical methane emissions.