Brenninkmeijer, C.A.M.

Kirner, O.

Ruhnke, R.

Schuck, T.

Slemr, F.

Sprung, D.

Zahn, A.

English

Brenninkmeijer, C. A. M.

KITopen

KIT – The cooperation of Forschungszentrum Karlsruhe GmbH and Universität Karlsruhe (TH)Climatology of acetone in the ex-TLConclusionSeasonal variation of OH-production around tropopauseThe ex-TL during CARIBICCARIBICChemical processing and transport of O3, CO, H2O, acetone, and acetonitrile in the UT/LMS inferred from long-term, high-resolutionobservations onboard the CARIBIC passenger aircraft Poster M09A. Zahn, D. Sprung (detlev.sprung@imk.fzk.de), O. Kirner, and R. Ruhnke 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.-100 -80 -60 -40 -20 0 20 40 60 80 100 120 140-40-200204060MadrasDenverTorontoHoustonSantiagoBuenos AiresSao PauloManilaGuangzhouLatitudeLongitudeFrankfurtIn 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)tropopauseFig. 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 dependence (red line observed at 42°E, green line at 69°E, both at ~50°N). The mixing reservoirs are well-defined. The vertical extension (thickness) of the ex-TL shows a seasonal variation, with ~1.6 km in winter and ~2.6 km in summer (not shown).Fig. 1: Schematic view of a typical tracer correlation around the extra-tropical 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 ones 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. Small acetone concentrations around the top of the ex-TL in summer indicate a transport time in the order of the local (chemical) life time of acetone of ~4 weeks (not shown)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-TLFig. 7: Seasonal cycle of the OH production due to the photolysis of O3 (red) and acetone (blue) at the TP (full circles) and 2 km above it (open circles). Photolysis rates of ozone and acetone were taken from the Messy model (MPI-C, Mainz), which are based on JPL recommendations.Year-around tropospheric air mixes into the extra-tropical lowermost stratosphere and forms a mixing layer, the ex-TL, sandwiched between upper tropospheric and clean stratospheric air. Our H2O data demonstrate that this in-mixing primarily occurs along isentropic surfaces (Fig. 4). Based on the lifetime of acetone a mixing time to altitudes at 2-3 km above the tropopause of ~4 weeks was inferred. Further constraints on the chemical processing and the ventilation of the extra-tropical tropopause region deliver trace gas climatologies, e.g. Fig. 6 for acetone. The seasonal variation of the production of OH near the mid-latitude tropopause was derived from the high-resolution CARIBIC acetone, O3, and H2O measurements. Both OH sources indicate a similar seasonal variation. At the tropopause, the photolysis of acetone even seems to dominate as OH source.Fig. 6: Seasonal variation of acetone around the tropo-pause inferred from the CARIBIC data 2005-2008.Jan Feb Mär Apr Mai Jun Jul Aug Sep Okt Nov Dez02000400060008000100001200014000160001800020000 acetone photolysis tropopause + 2kmOH molecules cm-3 s-1MonthO(1D) + H2O tropopause + 2kmIn Fig. 7 the seasonal cycle of the production of OH due to acetone is compared with the one caused by the photolysis of O3 and subsequent reaction of O(1D) with H2O (also measured in CARIBIC). Both OH sources show a similar seasonal variation with maxima in summer. Except of June (which appears to be an outlier), at the tropopause the photolysis of acetone exceeds the OH production due to the photolysis of ozone. Above the tropopause, this behavior quickly turns around, due to the step decrease of acetone in the stratosphere.A strong seasonal variation of acetone is observed in the ex-TL (Fig. 6). In autumn the gradient across the tropopause is weak. Elevated acetone values remain in the lowermost stratosphere until ~November when the subsidence of clean, O3-rich stratospheric air sets in.  

Chemical processing and transport of O₃, CO, H₂O acetone, and acetonitrile in the UT/LMS inferred from long-term, high-resolution observations onboard the CARIBIC passenger aircraft

https://publikationen.bibliothek.kit.edu/220074170/3815408

Chemical processing and transport of O₃, CO, H₂O acetone, and acetonitrile in the UT/LMS inferred from long-term, high-resolution observations onboard the CARIBIC passenger aircraft

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