Filamentary structure in chemical tracer distributions near the subtropical jet following a wave breaking event

Abstract

Abstract. This paper presents a set of observations and analyses of trace gas cross sections in the extratropical upper troposphere/lower stratosphere (UTLS). The spatially highly resolved (≈0.5 km vertically and 12.5 km horizontally) cross sections of ozone (O 3 ), nitric acid (HNO 3 ), and peroxyacetyl nitrate (PAN), retrieved from the measurements of the CRISTA-NF infrared limb sounder flown on the Russian M55-Geophysica, revealed intricate layer structures in the region of the subtropical tropopause break. The chemical structure in this region shows an intertwined stratosphere and troposphere. The observed filaments in all discussed trace gases are of a spatial scale of less than 0.8 km vertically and about 200 km horizontally across the jet stream. Backward trajectory calculations confirm that the observed filaments are the result of a breaking Rossby wave in the preceding days. An analysis of the trace gas relationships between PAN and O 3 identifies four distinct groups of air mass: polluted subtropical tropospheric air, clean tropical upper-tropospheric air, the lowermost stratospheric air, and air from the deep stratosphere. The tracer relationships further allow the identification of tropospheric, stratospheric, and the transitional air mass made of a mixture of UT and LS air. Mapping of these air mass types onto the geo-spatial location in the cross sections reveals a highly structured extratropical transition layer (ExTL). Finally, the ratio between the measured reactive nitrogen species (HNO 3 + PAN + ClONO 2 ) and O 3 is analysed to estimate the influence of tropospheric pollution on the extratropical UTLS.In combination, these diagnostics provide the first example of a multi-species two-dimensional picture of the inhomogeneous distribution of chemical species within the UTLS region. Since Rossby wave breaking occurs frequently in the region of the tropopause break, these observed fine-scale filaments are likely ubiquitous in the region. The implications of the layered structure for chemistry and radiation need to be examined, and the representation of this structure in chemistry-climate models is discussed.

Long-range transport pathways of tropospheric source gases originating in Asia into the northern lower stratosphere during the Asian monsoon season 2012

“…Therefore, the spatial structure of young air masses characterized by enhanced values of emission tracers from India/China resembles a bubble within the upper troposphere. These air masses are transported eastwards along the subtropical jet and most likely enter the extratropical lower stratosphere driven by Rossby wave breaking events associated with double tropopauses (e.g., Vaughan and Timmis, 1998;Castanheira and Gimeno, 2011;Ungermann et al, 2013;Homeyer and Bowman, 2013;Homeyer et al, 2014). Our simulations show that after entering the lower stratosphere, these air masses are mixed irreversibly with the surrounding stratospheric air.…”

“…Previous studies also found intrusions of tropospheric air into the lower stratosphere associated with extratropical double tropopauses (e.g., Pan et al, 2009;Homeyer et al, 2011;Vogel et al, 2011b;Schwartz et al, 2015;Wu and Lü, 2015). Further, it was shown that double tropopauses are frequently associated with Rossby wave breaking events along the subtropical jet (e.g., Vaughan and Timmis, 1998;Castanheira and Gimeno, 2011;Ungermann et al, 2013;Homeyer and Bowman, 2013;Homeyer et al, 2014).…”

Improving retrieval quality for airborne limb sounders by horizontal regularisation

“…The better reproduction of thin vertical layers is important for the analysis of mixing processes in the upper troposphere/lower stratosphere. The algorithm is therefore currently used to process further CRISTA-NF data (Ungermann et al, 2012b) and initial (non-tomographic) measurements by GLORIA (Gimballed Limb Observer for Radiance Imaging of the Atmosphere; see Ungermann et al, 2010b). This technique might also be used to more reliably derive constant and slowly varying instrument parameters, which cannot be determined from pre-or post-flight calibration.…”

An assessment of ozone mini-hole representation in reanalyses over the Northern Hemisphere

“…Studies of the characteristics of poleward advection of upper-tropospheric air have shown that such intrusions are associated with Rossby wave breaking in the upper troposphere (Peters and Waugh, 1996). In turn, poleward Rossby wave breaking has been associated with the presence of double tropopauses (DTs) (Pan et al, 2009;Castanheira and Gimeno, 2011;Homeyer et al, 2011;Ungermann et al, 2013). Further, climatological studies have found that DT occurrence in the Northern Hemisphere coincides with zones of storm track cyclogenesis (e.g., Añel et al, 2008;Peevey et al, 2012) and their occurrence frequency shows a strong seasonal variation peaking during winter (Randel et al, 2007;Manney et al, 2014), both char-acteristics displayed by the mini-hole events.…”