Brenninkmeijer, C.A.M.

Keller, J.

Schuck, T.

Slemr, F.

Sprung, D.

Zahn, A.

Brenninkmeijer, C. A. M.

KITopen

KIT – The cooperation of Forschungszentrum Karlsruhe GmbH and Universität Karlsruhe (TH)ConclusionVertical extension of ex-TLThe ex-TL during CARIBICCARIBICProperties of the extra-tropical tropopause transition layer (ex-TL) fromhigh-resolution O3, CO, H2O, acetone, and acetonitrile observationsonboard the CARIBIC passenger aircraft P109 / abstract 00410Andreas Zahn (andreas.zahn@imk.fzk.de), D. Sprung, J. Keller F. Slemr, T. Schuck, and C.A.M. BrenninkmeijerInstitute for Meteorology and Climate Research, Karlsruhe, Germany         Max-Planck Institute for Chemistry, Mainz, GermanyThe extratropical tropopause transition layer (ex-TL)… names a layer sandwiched at the lower border by the  tropopause and at the upper border by the unperturbed lowermost stratosphere (LMS) that is not influenced by recent in-mixing of tropospheric air. It is usually identified by linear or slightly curved correlations between a tropospheric tracer and a stratospheric tracer.The nature as well as many properties of the ex-TL (seasonal variation, turnover time, short-term variability, convection-induced impact) are badly quantified, yet. Likewise, its relation to the recently discovered and meteorologically defined tropopause inversion layer (TIL) is not known, yet.In CARIBIC a measurement container with 18 instruments is deployed once a month for four long-distance flights onboard an A340-600 of Lufthansa. Almost 100 trace gases and aerosol parameters are measured at typical flight altitudes of 9-12 km. Since May 2005, more than 100 measurements flights were carried out.05010015020025030035040045050055060065070075020 30 40 50 60 70 80 90 100 110 120 130 140CO (ppbv)Ozone (ppbv)333638414346485153Latitude (°N)0501001502002503003504004505004 10 100 1000H2O (ppmv)Ozone (ppbv)330334338342346350354358362pot. temperature (K)-1012340 200 400 600 800 1000 1200 1400 1600     6. February 2007 28. April 2006 22. June 2007 20. October 2006Acetone (pptv)altitude above O3 - TP (km)tropopauseJan Feb Mär Apr Mai Jun Jul Aug Sep Okt Nov Dez0.51.01.52.02.53.03.54.04.5ex-TL depth (km)MonthLatitude (°N)40 42 44 45 47 49 51 52 54Jan Feb Mär Apr Mai Jun Jul Aug Sep Okt Nov Dez0.51.01.52.02.53.03.54.04.53ex-TL depth (km)MonthLatitude (°N)32 35 38 41 44 47 50 53 56Fig. 3 shows a typical O3-CO correla-tion observed between China and Germany in February 2007.The mixing line or ex-TL, resp., is clearly visible with a weak spatial difference (red line observed at 42°E, green line at 69°E, both at ~50°N). The mixing reservoirs a well-defined. Fig. 1: Schematic view of a typical tracer correlation around the extratr. tropopauseFig. 2: Flight paths May 2005 – July 2008summerwinterFig. 4 indicates a typical H2O-CO correlation pattern observed in August 2006. The picture demonstrates that the mixing across the tropopause occurred along isentropic surfaces (lines). The blue data points characterize dry subtropical air, the black more humid high-latitude air. Note, the high H2O m.r. in the ex-TL.Fig. 5 shows the vertical profile of acetone relative to the tropopause for 4 flights in different seasons. There is a strong seasonal variation with highest acetone values and the highest variability in summer.Fig. 3: Correlation between O3 and CO for a 11-hour flight (~10000 km) between South China and Germany at 10-12 km altitudeFig. 4: Correlation between O3 and H2O for a 11-hour flight from China to Germany.ex-TLFig. 5: Vertical profiles of acetone observed in the mid-latitudes in different seasons.ex-TLex-TLThe vertical extension of the ex-TL shows a seasonal variation, with ~1.6 km in winter and ~2.6 km in summer, see right Fig. 6a for CO.For acetone (Fig. 6b) the high summer values are missing, which indicates that the air travel time from the tropopause to altitudes ~3km above the tropopause roughly amounts to the local lifetime of acetone of ~4 weeks. for COfor acetoneFig. 6: Vertical extension of ex-TL based on the correlation of O3 withCO (a) and acetone (b). Thedashed lines are running means, the shaded areas are sine functions that fit the data. No latitudinal gradient was resolved.Year-around tropospheric air mixes into the extra-tropical lowermost strato-sphere and forms a mixing layer, the ex-TL, sandwiched between upper tropo-spheric and clean stratospheric air. Our H2O data demonstrate that this in-mixing primarily occurs along isentropic surfaces (Fig. 4). A significant seasonal variation of the trace gas composition of the in-mixed air (Fig. 4, 5) and of the vertical extension of the ex-TL (Fig. 6) was observed. Based on the lifetime of acetone a mixing time to altitudes of 2-3 km above the tropopause of ~4 weeks was inferred. Further constraints on the ventilation of the lower-most stratosphere deliver trace gas climatologies, e.g. Fig. 7 for acetone.Fig. 7: Seasonal variation of acetone around the tropo-pause inferred from the CARIBIC data 2005-2008. A strong seasonal variation is observed. In autumn the gradient across the tropo-pause is weak. Elevated acetone values remain in the lowermost stratosphere until ~November when the subsidence of clean, O3-rich stratospheric air sets in.

Properties of the extra-tropical tropopause transition layer (ex-TL) from high-resolution O₃, CO, H₂O, acetone, and acetonitrile observations onboard the CARIBIC passenger aircraft

https://publikationen.bibliothek.kit.edu/220074171/3815409

Properties of the extra-tropical tropopause transition layer (ex-TL) from high-resolution O₃, CO, H₂O, acetone, and acetonitrile observations onboard the CARIBIC passenger aircraft

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