Observation of near‐zero ozone concentrations in the upper troposphere at mid‐latitudes

Abstract

Abstract. Measurements by an ECC ozonesonde launched from Aberystwyth (52.4øN, -4.1øE) in July show ozone concentrations decreasing steadily from a warm frontal surface to the tropopause, cumulating in a layer-0.5 km deep with near-zero ozone concentrations at 12 km. Such features have previously been detected by lidar but have not been reported in ozonesonde data at mid-latitudes; they have, however, been found in ozonesonde profiles above the equatorial Pacific. We examine three possible hypotheses for the origin of the ozone-free air: in situ destruction by cirrus clouds, rapid transport from the marine boundary layer in the extratropics and long-range transport from the tropics. We conclude that the ozone-poor air observed on this day could only have resulted from long-range transport from the tropics.

Tropospheric Halogen Chemistry

“…Ongoing work is estimating tropospheric vertical columns of BrO from satellite data but is expected to yield reliable data only in the polar regions or other regions of strongly elevated BrO (J. Hollwedel, personal communication). A similar event was discussed by Davies et al (1998), where near-zero O 3 concentrations were encountered in the mid-latitude upper troposphere. They include organohalogens (e.g., CH 3 Br, CH 2 Br 2 , CHBr 3 , and CHBr 2 Cl), which are broken down by photolysis and/or reaction with OH, release from sea salt aerosol and upward transport from the MBL, downward transport from the stratosphere in mid-to high latitudes, 'spill-out' and uplifting from polar surface ODEs, volcanoes, salt lakes, especially at high altitude (such as the Salar de Uyuni), release of inorganic halogens by biomass burning, or other, so far unidentified processes.…”

Observations of rapid photochemical destruction of ozone in snowpack interstitial air

“…Some recent measurements of the amplitude and shape of the diurnal cycle of ozone in the remote marine boundary layer cannot be explained by free tropospheremarine boundary layer (MBL) transport, or by standard photochemical models [Nagao et al, 1999;Dickerson et al, 1999]. In addition, other measurements show that ozone levels are occasionally very depleted in association with midlatitude cirrus clouds [Reichardt et al, 1996;Davies et al, 1998]. Catalytic ozone destruction by reaction with halogens derived from sea-salt aerosols has been proposed to explain some of the unusual features in the ozone diurnal cycle in the MBL [Nagao et al, 1999;Dickerson et al, 1999].…”

“…In contrast, both unspecified heterogeneous reactions on ice [Reichardt et al, 1996] and long-range transport of ozonedepleted air from lower latitudes [Davies et al, 1998] have been proposed to explain the ozone depletions associated with cirrus clouds. Ozone deposition to dark ice surfaces is too slow to be significant [Langenberg and Schurath, 1999].…”

Aircraft Observation of CO₂, CO₂ O₃ and H₂ over the North Pacific during the PACE-7 Campaign

“…8). Near-zero O 3 was found between 10 km and the tropopause over the equatorial Pacific (Kley et al, 1996) and at about 12 km at mid-latitudes (Davies et al, 1998) by balloon-borne soundings. However, there have been few observational results of extremely low O 3 into the upper troposphere in the subtropics.…”