edu.ucar.opensky::articles:21204 UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact 2025-12-26T02:25:23.572325 ISO 19115-2 Geographic Information - Metadata - Part 2: Extensions for Imagery and Gridded Data ISO 19115-2:2009(E) https://n2t.org/ark:/85065/d7zp48qz New insights into the column CH2O/NO2 ratio as an indicator of near-surface ozone sensitivity 2017-08-27T00:00:00Z publication https://n2t.org/ark:/85065/d7zp48qz https://doi.org/10.1002/2017JD026781 Schroeder, J. R. author Crawford, J. H. author Fried, A. author Walega, J. author Weinheimer, Andrew author Wisthaler, A. author Müller, M. author Mikoviny, T. author Chen, G. author Shook, M. author Blake, D. R. author Tonnesen, G. S. author UCAR/NCAR - Library publisher Satellite-based measurements of the column CH2O/NO2 ratio have previously been used to estimate near-surface ozone (O-3) sensitivity (i.e., NOx or VOC limited), and the forthcoming launch of air quality-focused geostationary satellites provides a catalyst for reevaluating the ability of satellite-measured CH2O/NO2 to be used in this manner. In this study, we use a 0-D photochemical box model to evaluate O-3 sensitivity and find that the relative rate of radical termination from radical-radical interactions to radical-NOx interactions (referred to as LROx/LNOx) provides a good indicator of maximum O-3 production along NOx ridgelines. Using airborne measurements from NASA's Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relative to Air Quality (DISCOVER-AQ) deployments in Colorado, Maryland, and Houston, we show that in situ measurements of CH2O/NO2 can be used to indicate O-3 sensitivity, but there is an important "transition/ambiguous" range whereby CH2O/NO2 fails to categorize O-3 sensitivity, and the range and span of this transition/ambiguous range varies regionally. Then, we apply these findings to aircraft-derived column density measurements from DISCOVER-AQ and find that inhomogeneities in vertical mixing in the lower troposphere further degrades the ability of column CH2O/NO2 to indicate near-surface O-3 sensitivity (i.e., the transition/ambiguous range is much larger than indicated by in situ data alone), and we hypothesize that the global transition/ambiguous range is sufficiently large to make the column CH2O/NO2 ratio unuseful for classifying near-surface O-3 sensitivity. Lastly, we present a case study from DISCOVER-AQ-Houston that suggests that O-3 sensitivity on exceedance days may be substantially different than on nonexceedance days (which may be observable from space) and explore the diurnal evolution of O-3 sensitivity, O-3 production, and the column CH2O/NO2 ratio. The results of these studies suggest that although satellite measurements of CH2O/NO2 alone may not be sufficient for accurately classifying near-surface O-3 sensitivity, new techniques offered by geostationary platforms may nonetheless provide methods for using space-based measurements to develop O-3 mitigation strategies. UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact PDF Text theme Resource Type 2016-01-01T00:00:00Z publication Copyright 2017 American Geophysical Union. None eng geoscientificInformation