Abstract
[1] We study the mechanisms driving stratosphere-troposphere exchange of ozone fluxes within a chemistry-transport model. For years 2004–2006, year-round, most of the stratosphere-to-troposphere flux of O3 is associated with shear and folding around the subtropical jet, and this jet-related flux peaks for the northern hemisphere in May. Over the northern mid-latitude continents, however, surface convection penetrates to stratospheric levels of O3 (250 ppb), enhancing the O3 flux by 19% of the northern hemisphere total, and shifting the peak flux to June. This convection-related O3 flux represents 49% of the total over northern mid-latitudes in June.
Highlights
[5] In our chemistry‐transport modeling (CTM) of ozone [Tang and Prather, 2010], we find a small number of convective events reach into the lower stratosphere where O3 abundances exceed 250 ppb, eroding the lower stratosphere through direct mixing of tropospheric air and induced subsidence, and driving an Stratosphere‐troposphere exchange (STE) O3 flux
We diagnose the STE flux driven by deep convection and show how it shifts the seasonality of the O3 flux entering the northern hemisphere (NH) troposphere
O3 flux across 120‐ppb O3 surface per gram of air convected to O3 > 250 ppb (r2 = 0.9), describes a general relationship that applies to all latitudes in this model study and can be used to derive the STE O3 flux that is attributable to deep convection
Summary
[2] Quantifying the exchange of ozone (O3) and water vapor between the stratosphere and the troposphere is important due to their key roles as greenhouse gases and chemical active species in the upper troposphere and lower stratosphere (UT/LS). More recently STE has been attributed to mid‐ latitude deep convection [Poulida et al, 1996; Fischer et al, 2003; Gray, 2003; Hegglin et al, 2004]. In these large organized convective systems, the mesoscale ageostrophic movements and tropopause deformation around the convective region result in STE and ozone enhancement in the free troposphere. In addition to these large organized systems, deep convection over summer continents in individual cells is capable of reaching and/or penetrating the tropopause. We diagnose the STE flux driven by deep convection and show how it shifts the seasonality of the O3 flux entering the NH troposphere
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