Our interests include interactions between vegetation and atmospheric chemistry, climate, and air pollution.
Impacts of dry deposition on atmospheric composition
We investigated the role of dry deposition, an often overlooked yet important loss pathway for numerous trace species, and its variations with meteorology and land use, in shaping observed distributions of ozone over the eastern United States. We used measurements from northern mid-latitude eastern U.S. forests and process-level models to advance the understanding of temporal variability in vegetative uptake of ozone, an air pollutant and greenhouse gas (Clifton et al., 2017 and 2019). By coupling dry deposition in a chemistry-climate model with a dynamic vegetation model that includes land-use transitions, we examined variability in the dry depositional sink on time scales ranging from hours to decades, including during extreme climate and pollution events (Clifton et al., 2020a). We also found that interpreting observed ground-level ozone trends in terms of ozone precursor emission changes is likely sensitive to any large-scale changes in dry deposition (Baublitz et al., 2020). Our review on the processes controlling dry deposition over land is available here (Clifton et al., 2020b). [NSF Graduate Research Fellowship to Olivia Clifton; NOAA]
Isoprene oxidation chemistry, and its resulting impacts on atmospheric chemistry and air pollution, depends strongly on NOx. We examined the potential for combined analysis of trace gas columns retrieved from space-based instruments to provide information on the spatial and temporal variability of isoprene oxidation (as well as methane and other volatile organic compounds). Valin et al. (2015) describe a role for OH... in interpreting variability in formaldehyde columns over the Southeast US.
[NOAA Postdoctoral Fellowship to Luke Valin 2013-2015]
Drought and Surface Ozone Precursors
We analyze 2005–2015 tropospheric column concentrations of two trace gases that serve asproxies for surface ozone precursors retrieved from the OMI/Aura satellite: Nitrogen dioxide (a NO x proxy) and formaldehyde (a VOC proxy) over the eastern U.S.A. While higher temperatures during droughts are usually associated with observed increases in trace gas concentrations, in the Southeast US we find increases associated with low precipitation independent of temperature. (Naimark et al., 2021). [NASA, Columbia University]