Phys.org November 1, 2021
The hydroxyl radical (OH) sets the oxidative capacity of the atmosphere and thus, profoundly affects the removal rate of pollutants and reactive greenhouse gases. OH estimates for past and future periods rely primarily on global atmospheric chemistry models. The models disagree ± 30% in mean OH and in its changes from the preindustrial to late 21st century. A simple steady-state relationship that accounts for ozone photolysis frequencies, water vapor, and the ratio of reactive nitrogen to carbon emissions explains temporal variability within most models, but not intermodal differences. A team of researchers in the US (University of Rochester, Columbia University, Duke University, NOAA) showed that departure from the expected relationship reflects the treatment of reactive oxidized nitrogen species (NOy) and the fraction of emitted carbon that reacts within each chemical mechanism, which remain poorly known due to a lack of observational data. Their findings imply a need for additional observational constraints on NOy partitioning and lifetime, especially in the remote free troposphere, as well as the fate of carbon-containing reaction intermediates to test models, thereby reducing uncertainties in projections of OH…read more. TECHNICAL ARTICLEÂ