Stratosphere‐Troposphere Exchange of Air Masses and Ozone Concentrations Based on Reanalyses and Observations

Abstract

Stratosphere-troposphere exchange (STE) of ozone represents a significant source for the tropospheric ozone budget (e.g.,

Stratosphere‐Troposphere Exchanges of Air Mass and Ozone Concentration in the Last Glacial Maximum

“…In this study, we propose the dynamic upper isentrope method (Figure 1c) that uses a dynamic isentropic surface as the upper boundary of the lowermost stratosphere, which is determined by fitting to the tropical lapse rate tropopauses (WMO, 1957) in different climates. This is distinctly different from a constant 380 K isentrope used in Appenzeller et al (1996) (Figure 1a) and Wang and Fu (2021) (Figure 1b). The dynamic upper isentropic surface (red solid line in Figure 1c) is determined by minimizing the difference between the isentropic levels ranging from 360 to 390 K with a 1 K interval and the lapse rate tropopause over the regions equatorward of the latitudes with zero tropopause diabatic heating.…”

“…Although the approach of Wang and Fu (2021) might not be suitable to derive the changes in air mass and ozone STEs over extratropics and tropics for different climates, it can derive the global STEs accurately (Wang & Fu, 2021). Table 3 shows the global ozone STEs in the PI, LGM PMIP3 , and LGM PROXY using the Wang and Fu (2021) method. There is excellent agreement for the global tropopause net ozone fluxes using the dynamic upper isentrope method (i.e., 367, 291, and 312 Tg year −1 during the PI, LGM PMIP3 , and LGM PROXY , respectively) and Wang and Fu (2021) method (i.e., 367, 287, and 308 Tg year −1 , correspondingly).…”

“…The strong anticyclonic vortex in the upper troposphere and lower stratosphere associated with the Asian summer monsoon can contribute to this horizontal transport between the extratropics and the tropics (Randel & Jensen, 2013;Randel et al, 2010). Those horizontal fluxes across the gaps, however, do not have any impact on the estimated global air mass and ozone STEs (Wang & Fu, 2021). On the other hand, in Appenzeller et al (1996) method (Figure 1a), the boundaries between the extratropics and tropics are the cross points between the 3.5 PVU tropopause and the 380 K isentrope that is considered as the tropical tropopause, which are at ∼20°N/S.…”

“…Figure S2 in Supporting Information S1). See Wang and Fu (2021) for the comparison of the Appenzeller et al (1996) and the Wang and Fu (2021) methods.…”

“…Figure 1 shows a schematic of the components involved in the air mass and ozone STEs for the methods of (a) Appenzeller et al (1996), (b) Wang and Fu (2021), and (c) the present study. In the lowermost stratosphere mass budget approach, the 380 K isentropic surface just lying above the tropopause in the tropics (e.g., Holton et al, 1995), is often used as the upper boundary of the lowermost stratosphere (e.g., Appenzeller et al, 1996;Schoeberl, 2004;Olsen et al, 2004Olsen et al, , 2013Wang & Fu, 2021;Yang et al, 2016). However, for different climates, the upper boundary of the lowermost stratosphere is also expected to change with the tropical tropopause.…”