A case study relating high ground level ozone to enhanced photochemistry and isentropic transport from the stratosphere

Abstract

Exceptionally high ozone ground level concentrations (>200 ppb) observed in Denver, Colorado, on the afternoon of March 4, 1978, are explained in terms of enhanced photochemistry combined with isentropic transport of ozone from the stratosphere. The maximum ozone concentrations observed on March 4 is the highest recorded for the 1975-1978 period. Inspection of the local pollutant and meteorological data shows high early morning accumulation of precursor gases and enhanced potential for afternoon photochemical activity. Objective cross-sectional analysis and trajectories on isentropic surfaces indicate that some air parcels that mixed into the boundary layer over the city on the afternoon of March 4 were derived from a stratospheric intrusion 3 days earlier. It is concluded that a combination of these factors resulted in the exceptionally high ozone concentrations.

First simultaneous measurements of ozone, CO, and NOy at a high‐altitude regional representative site in the central Himalayas

“…Downward transport of ozone is shown to contribute significantly to ozone variations observed over alpine sites, the Himalayas, the Tibetan Plateau, western United States, and western Europe [e.g., Stohl et al, 2003;Ding and Wang, 2006;Langford et al, 2009;Kumar et al, 2010]. Though STT influences the ozone levels in the middle to upper troposphere occasionally, it can deeply penetrate down to the lower troposphere and can enhance near-surface ozone levels [Ludwig et al, 1977;Haagenson et al, 1981;Stohl et al, 2000;Cooper et al, 2005;Akriditis et al, 2010;Lin et al, 2012a].…”

Stratospheric influence on surface ozone in the Los Angeles area during late spring and early summer of 2010

“…Stratospheric intrusions have long been linked to short‐lived increases in surface O 3 [ Chung and Dann , 1985; Haagenson et al , 1981; Mukammal et al , 1985; Viezee et al , 1983], particularly at higher elevations [ Ambrose et al , 2011; Davies and Schuepbach , 1994; Langford et al , 2009a; Stohl et al , 2000]. The importance of STT as a source for surface O 3 remains highly uncertain, however.…”

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“…It is then transported towards the equator by baroclinic waves and is folded into the atmosphere by amplifying vortices. Other investigators (Wolff et al, 1977;Haagenson, 1981;Husian et al, 1977) have confirmed these observations. …”