Stratosphere‐troposphere exchange of mass and ozone

Abstract

[1] This study examines the relationship between the extratropical cross-tropopause fluxes of mass and ozone. The adiabatic and diabatic components of the net fluxes are also compared. The rate of change of mass in the lowermost stratosphere and the flux across the 380 K isentropic surface are used to determine the net tropopause mass flux in the framework of a global circulation model. The diabatic mass flux is calculated from the heating rate at the tropopause, and the adiabatic component is determined by the difference of the net and diabatic fluxes. Consistent ozone fields are obtained by driving the Goddard Chemistry and Transport Model with meteorological output of the global circulation model for the same years. The ozone flux is determined by convolving the mass flux and ozone mixing ratio. The results show the following: (1) The seasonal cycle of the ozone mixing ratio is out of phase with the transport cycle leading to a temporal offset of the mass and ozone fluxes; (2) the downward net diabatic flux of mass and ozone occurs primarily at middle latitudes while the adiabatic mass flux is dominated by troposphere-tostratosphere transport at higher latitudes; and (3) the Southern Hemisphere stratospheric vortex is more effective at blocking meridional transport, resulting in a phase difference of mean tropopause ozone mixing ratio in the higher Southern Hemisphere latitudes with respect to the corresponding Northern Hemisphere season and location. Finally, this study suggests that individual pathways of cross-tropopause transport are unlikely to be the result of simultaneous adiabatic and diabatic mechanisms.

The governing processes and timescales of stratosphere-to-troposphere transport and its contribution to ozone in the Arctic troposphere

“…This is important for this study because the magnitude and seasonal cycle of STE is strongly tied to the Brewer-Dobson circulation through the overworld wave driving (Holton et al, 1995). Olsen et al (2004) showed that the exchange of mass and ozone between the stratosphere and troposphere in a CTM simulation driven with the GEOS-4 GCM meteorological fields compares well with estimates derived from observations. In comparison, a CTM simulation using an older version of the GEOS-4 Data Assimilation System (GEOS-4 DAS) produces a "fast" Brewer-Dobson circulation and "young" age of air as compared to the observations .…”

“…The flux of a trace gas across the tropopause is determined by the convolution of air mass flux and its concentration in the LS (Olsen et al, 2004). The comparison between DT fix , with constant mixing ratio above the tropopause, and DT 6−month , with a specified annual cycle above the tropopause, segregates the contribution from seasonal changes in mass flux (Fig.…”

Multi-model study of mercury dispersion in the atmosphere: vertical and interhemispheric distribution of mercury species

“…This feature was observed on all three flights during spring and thus seems not to be an individual outlier. Furthermore, in the time from April to July stratospheric mass transport into the upper and mid-troposphere is known to occur regularly (Appenzeller and Holten, 1996;Allen et al, 2003;Zanis et al, 2003;Olsen et al, 2004;Schoeberl, 2004). Moreover, Sprenger et al (2003) and Sprenger and Wernli (2003) demonstrated that cross-tropopause mass flux is highest in the midlatitudes where these mercury profiles were measured.…”

Climatology and long-term evolution of ozone and carbon monoxide in the UTLS at northern mid-latitudes, as seen by IAGOS from 1995 to 2013

“…winter. This feature is followed by approximately 100 days of transport until reaching the tropopause (Olsen et al, 2004 Olsen et al (2013, Fig. 5), where observations of O 3 mixing ratio in the stratosphere (θ = 380 K) from Microwave Limb Sounder (MLS) are combined with MERRA reanalysis meteorological fields.…”