Influence of isentropic transport on seasonal ozone variations in the lower stratosphere and subtropical upper troposphere

Abstract

[1] The isentropic cross-tropopause ozone transport has been estimated in both hemispheres in 1999 based on the potential vorticity mapping of Stratospheric Aerosol and Gas Experiment II ozone measurements and contour advection calculations using the NASA Goddard Space Flight Center Global and Modeling Assimilation Office analysis. The estimated net isentropic stratosphere-to-troposphere ozone flux is $118 ± 61 Â 10 9 kg yr À1 globally within the layer between 330 and 370 K in 1999; 60% of it is found in the Northern Hemisphere, and 40% is found in the Southern Hemisphere. The monthly average ozone fluxes are strongest in summer and weakest in winter in both hemispheres. The seasonal variations of ozone in the lower stratosphere (LS) and upper troposphere (UT) have been analyzed using ozonesonde observations from ozonesonde stations in the extratropics and subtropics, respectively. It is shown that observed ozone levels increase in the UT over subtropical ozonesonde stations and decrease in the LS over extratropical stations in late spring/early summer and that the ozone increases in the summertime subtropical UT are unlikely to be explained by photochemical ozone production and diabatic transport alone. We conclude that isentropic transport is a significant contributor to ozone levels in the subtropical upper troposphere, especially in summer.

Rossby Wave Breaking and Isentropic Stratosphere‐Troposphere Exchange During 1981–2015 in the Northern Hemisphere

“…The isentropic transport of air is stronger in the direction from S‐T than in the direction from T‐S in the midlatitudes (Dethof, O'Neill, Slingo, ; Sprenger & Wernli, ; Yang et al, ). Our results for STE during 1981–2015 extend the findings of Jing et al (, ), which looked at the isentropic exchange of ozone in individual years 1990 and 1999. The results of this study confirm that the isentropic STE occurs primarily where RWB occurs, indicating that RWB is a primary driver for isentropic transport.…”

Space‐based constraints on the production of nitric oxide by lightning

“…The enhancement in the northern hemisphere during July is driven by photochemical production from anthropogenic emissions [ Fishman and Brackett , 1997]. Enhancements at ±30° are due to a combination of subsidence from the stratosphere and photochemical production [ Li et al , 2002; Jing et al , 2005].…”

Influence of the Antarctic Ozone Hole over South of Brazil in 2010 and 2011

“…e domain of the Antarctic polar vortex and its laments was de ne as being the region with high PV gradient, where air masses with lower PV than the boundary of the outside region were included inside the vortex, conserving di erences chemical characteristics, and the center of the vortex with the minimum PV region or maximum Absolute PV (APV) (Marchand et al, 2005). e PV variation over isentropic surfaces can be used to transport ozone in stratosphere (Jing et al, 2005). An increase at the APV indicated a polar origin of the poor ozone air mass (Narayana Rao et al, 2003;Semane et al, 2006).…”