Observations of ozone-poor air in the Tropical Tropopause Layer Journal Article uri icon

Overview

abstract

  • Abstract. Ozonesondes reaching the tropical tropopause layer (TTL) over the West Pacific have occasionally measured layers of very low ozone concentrations – less than 15 ppbv – raising the question of how prevalent such layers are and how they are formed. In this paper we examine aircraft measurements from the ATTREX, CAST and CONTRAST campaigns based in Guam in January–March 2014 for evidence of very low ozone concentrations and their relation to deep convection. The study builds on results from the ozonesonde campaign conducted from Manus Island, Papua New Guinea, as part of CAST, where ozone concentrations as low as 12 ppbv were observed between 100 and 150 hPa downwind of a deep convective complex. TTL measurements from the Global Hawk unmanned aircraft show a marked contrast between the hemispheres, with mean ozone concentrations in profiles in the Southern Hemisphere between 100 hPa and 150 hPa of between 10.5 ppbv and 14.2 ppbv. By contrast, the mean ozone concentrations in profiles in the Northern Hemisphere were always above 15 ppbv and normally above 20 ppbv at these altitudes. The CAST and CONTRAST aircraft sampled the atmosphere between the surface and 120 hPa, finding very low ozone concentrations only between the surface and 700 hPa; mixing ratios as low as 7 ppbv were regularly measured in the boundary layer, whereas in the free troposphere above 200 hPa concentrations were generally well in excess of 15 ppbv. These results are consistent with uplift of almost-unmixed boundary layer air to the TTL in deep convection. An interhemispheric difference was found in the TTL ozone concentrations, with values ;

publication date

  • October 27, 2017

has restriction

  • green

Date in CU Experts

  • June 24, 2021 5:49 AM

Full Author List

  • Newton R; Vaughan G; Hintsa E; Filus MT; Pan LL; Honomichl S; Atlas E; Andrews SJ; Carpenter LJ

author count

  • 9

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