September 29, 2016
The Tropospheric Oxidizing Capacity: Current Challenges and Future Prospects
Hydroxyl radical, OH, is the primary tropospheric oxidant. It determines the rate of removal, and controls the abundance, of most trace gas species, including methane. It also leads to the formation of the short-lived climate forcing species, ozone and aerosols. Simulated global mean OH varies by about 100%, with uncertainties expected to be much higher on regional scale related to the larger variability in OH sources and sinks. This leads to uncertainties in the lifetime of methane, which varies between models from ~7 to ~14 years. While OH is typically well simulated, compared to measurements, in urban polluted regions, it is significantly underestimated in high isoprene and remote regions. In this presentation we will explore the current understanding of tropospheric OH chemistry, known and unknowns and their uncertainties. We will also highlight new updates in OH sources and recycling, which will re-shape the known OH chemistry and in the next few years, with impacts on methane lifetime and chemistry climate interactions.