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Start date: 2010 × DDC: 550 × Subject: lidar × Subject: troposphere × WGL Institute: IAP ×

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Now showing 1 - 2 of 2
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    Is the near-spherical shape the "new black" for smoke?
    (Katlenburg-Lindau : EGU, 2020) Gialitaki, Anna; Tsekeri, Alexandra; Amiridis, Vassilis; Ceolato, Romain; Paulien, Lucas; Kampouri, Anna; Gkikas, Antonis; Solomos, Stavros; Marinou, Eleni; Haarig, Moritz; Baars, Holger; Ansmann, Albert; Lapyonok, Tatyana; Lopatin, Anton; Dubovik, Oleg; Groß, Silke; Wirth, Martin; Tsichla, Maria; Tsikoudi, Ioanna; Balis, Dimitris
    We examine the capability of near-sphericalshaped particles to reproduce the triple-wavelength particle linear depolarization ratio (PLDR) and lidar ratio (LR) values measured over Europe for stratospheric smoke originating from Canadian wildfires. The smoke layers were detected both in the troposphere and the stratosphere, though in the latter case the particles presented PLDR values of almost 18% at 532 nm as well as a strong spectral dependence from the UV to the near-IR wavelength. Although recent simulation studies of rather complicated smoke particle morphologies have shown that heavily coated smoke aggregates can produce large PLDR, herein we propose a much simpler model of compact near-spherical smoke particles. This assumption allows for the reproduction of the observed intensive optical properties of stratospheric smoke, as well as their spectral dependence. We further examine whether an extension of the current Aerosol Robotic Network (AERONET) scattering model to include the near-spherical shapes could be of benefit to the AERONET retrieval for stratospheric smoke cases associated with enhanced PLDR. Results of our study illustrate the fact that triple-wavelength PLDR and LR lidar measurements can provide us with additional insight when it comes to particle characterization. © 2020 Author(s).
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    On the upper tropospheric formation and occurrence of high and thin cirrus clouds during anticyclonic poleward Rossby wave breaking events
    (Milton Park : Taylor & Francis, 2010) Eixmann, Ronald; Peters, Dieter H.W.; Zülicke, Christoph; Gerding, Michael; Dörnbrack, Andreas
    Ground-based lidar measurements and balloon soundings were employed to examine the dynamical link between anticyclonic Rossby wave breaking and cirrus clouds from 13 to 15 February 2006. For this event, an air mass with low Ertel’s potential vorticity appeared over Central Europe. In the tropopause region, this air mass was accompanied with both an area of extreme cold temperatures placed northeastward, and an area of high specific humidity, located southwestward. ECMWF analyses reveal a strong adiabatic northeastward and upward transport of water vapour within the warm conveyor belt on the western side of the ridge over Mecklenburg, Northern Germany. The backscatter lidar at K¨uhlungsborn (54.1◦N, 11.8◦E) clearly identified cirrus clouds at between 9 and 11.4 km height. In the tropopause region high-vertical resolution radiosoundings showed layers of subsaturated water vapour over ice but with a relative humidity over ice >80%. Over Northern Germany radiosondes indicated anticyclonically rotating winds in agreement with backward trajectories of ECMWF analyses in the upper troposphere, which were accompanied by a relatively strong increase of the tropopause height on 14 February. Based on ECMWF data the strong link between the large-scale structure, updraft and ice water content was shown.