New insights into the column CH2O/NO2 ratio as an indicator of near-surface ozone sensitivity

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.