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- ItemExtreme levels of Canadian wildfire smoke in the stratosphere over central Europe on 21-22 August 2017(Katlenburg-Lindau : EGU, 2018) Ansmann, Albert; Baars, Holger; Chudnovsky, Alexandra; Mattis, Ina; Veselovskii, Igor; Haarig, Moritz; Seifert, Patric; Engelmann, Ronny; Wandinger, UllaLight extinction coefficients of 500 Mm1, about 20 times higher than after the Pinatubo volcanic eruptions in 1991, were observed by European Aerosol Research Lidar Network (EARLINET) lidars in the stratosphere over central Europe on 21-22 August 2017. Pronounced smoke layers with a 1-2 km vertical extent were found 2-5 km above the local tropopause. Optically dense layers of Canadian wildfire smoke reached central Europe 10 days after their injection into the upper troposphere and lower stratosphere which was caused by rather strong pyrocumulonimbus activity over western Canada. The smoke-related aerosol optical thickness (AOT) identified by lidar was close to 1.0 at 532 nm over Leipzig during the noon hours on 22 August 2017. Smoke particles were found throughout the free troposphere (AOT of 0.3) and in the pronounced 2 km thick stratospheric smoke layer at an altitude of 14-16 km (AOT of 0.6). The lidar observations indicated peak mass concentrations of 70-100 μgm-3 in the stratosphere. In addition to the lidar profiles, we analyzed Moderate Resolution Imaging Spectroradiometer (MODIS) fire radiative power (FRP) over Canada, and the distribution of MODIS AOT and Ozone Monitoring Instrument (OMI) aerosol index across the North Atlantic. These instruments showed a similar pattern and a clear link between the western Canadian fires and the aerosol load over Europe. In this paper, we also present Aerosol Robotic Network (AERONET) sun photometer observations, compare photometer and lidar-derived AOT, and discuss an obvious bias (the smoke AOT is too low) in the photometer observations. Finally, we compare the strength of this recordbreaking smoke event (in terms of the particle extinction coefficient and AOT) with major and moderate volcanic events observed over the northern midlatitudes.
- ItemIs 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, DimitrisWe 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).
- Item1064nm rotational Raman lidar for particle extinction and lidar-ratio profiling: Cirrus case study(München : European Geopyhsical Union, 2016) Haarig, Moritz; Engelmann, Ronny; Ansmann, Albert; Veselovskii, Igor; Whiteman, David N.; Althausen, DietrichFor the first time, vertical profiles of the 1064 nm particle extinction coefficient obtained from Raman lidar observations at 1058 nm (nitrogen and oxygen rotational Raman backscatter) are presented. We applied the new technique in the framework of test measurements and performed several cirrus observations of particle backscatter and extinction coefficients, and corresponding extinction-to-backscatter ratios at the wavelengths of 355, 532, and 1064 nm. The cirrus backscatter coefficients were found to be equal for all three wavelengths keeping the retrieval uncertainties in mind. The multiple-scattering-corrected cirrus extinction coefficients at 355 nm were on average about 20–30 % lower than the ones for 532 and 1064 nm. The cirrus-mean extinction-to-backscatter ratio (lidar ratio) was 31 ± 5 sr (355 nm), 36 ± 5 sr (532 nm), and 38 ± 5 sr (1064 nm) in this single study. We further discussed the requirements needed to obtain aerosol extinction profiles in the lower troposphere at 1064 nm with good accuracy (20 % relative uncertainty) and appropriate temporal and vertical resolution.
- ItemProfiles of cloud condensation nuclei, dust mass concentration, and ice-nucleating-particle-relevant aerosol properties in the Saharan Air Layer over Barbados from polarization lidar and airborne in situ measurements(Katlenburg-Lindau : EGU, 2019) Haarig, Moritz; Walser, Adrian; Ansmann, Albert; Dollner, Maximilian; Althausen, Dietrich; Sauer, Daniel; Farrell, David; Weinzierl, BernadettThe present study aims to evaluate lidar retrievals of cloud-relevant aerosol properties by using polarization lidar and coincident airborne in situ measurements in the Saharan Air Layer (SAL) over the Barbados region. Vertical profiles of the number concentration of cloud condensation nuclei (CCN), large particles (diameter d > 500 nm), surface area, mass, and ice-nucleating particle (INP) concentration are derived from the lidar measurements and compared with CCN concentrations and the INP-relevant aerosol properties measured in situ with aircraft. The measurements were performed in the framework of the Saharan Aerosol Longrange Transport and Aerosol-Cloud-Interaction Experiment (SALTRACE) in summer 2013. The CCN number concentrations derived from lidar observations were up to a factor of 2 higher than the ones measured in situ aboard the research aircraft Falcon. Possible reasons for the difference are discussed. The number concentration of particles with a dry radius of more than 250 nm and the surface-area concentration obtained from the lidar observations and used as input for the INP parameterizations agreed well (< 30 %-50 % deviation) with the aircraft measurements. In a pronounced lofted dust layer during summer (10 July 2013), the lidar retrieval yielded 100-300 CCN per cubic centimeter at 0.2 % water supersaturation and 10-200 INPs per liter at-25?C. Excellent agreement was also obtained in the comparison of mass concentration profiles. During the SALTRACE winter campaign (March 2014), the dust layer from Africa was mixed with smoke particles which dominated the CCN number concentration. This example highlights the unique lidar potential to separate smoke and dust contributions to the CCN reservoir and thus to identify the sensitive role of smoke in trade wind cumuli developments over the tropical Atlantic during the winter season. © 2017 Georg Thieme Verlag. All rights reserved.
- ItemTriple-wavelength depolarization-ratio profiling of Saharan dust over Barbados during SALTRACE in 2013 and 2014(Katlenburg-Lindau : EGU, 2017) Haarig, Moritz; Ansmann, Albert; Althausen, Dietrich; Klepel, André; Groß, Silke; Freudenthaler, Volker; Toledano, Carlos; Mamouri, Rodanthi-Elisavet; Farrell, David A.; Prescod, Damien A.; Marinou, Eleni; Burton, Sharon P.; Gasteiger, Josef; Engelmann, Ronny; Baars, HolgerTriple-wavelength polarization lidar measurements in Saharan dust layers were performed at Barbados (13.1°N, 59.6°W), 5000-8000km west of the Saharan dust sources, in the framework of the Saharan Aerosol Long-range Transport and Aerosol-Cloud-Interaction Experiment (SALTRACE-1, June-July 2013, SALTRACE-3, June-July 2014). Three case studies are discussed. High quality was achieved by comparing the dust linear depolarization ratio profiles measured at 355, 532, and 1064nm with respective dual-wavelength (355, 532nm) depolarization ratio profiles measured with a reference lidar. A unique case of long-range transported dust over more than 12000km is presented. Saharan dust plumes crossing Barbados were measured with an airborne triple-wavelength polarization lidar over Missouri in the midwestern United States 7 days later. Similar dust optical properties and depolarization features were observed over both sites indicating almost unchanged dust properties within this 1 week of travel from the Caribbean to the United States. The main results of the triple-wavelength polarization lidar observations in the Caribbean in the summer seasons of 2013 and 2014 are summarized. On average, the particle linear depolarization ratios for aged Saharan dust were found to be 0.252±0.030 at 355nm, 0.280±0.020 at 532nm, and 0.225±0.022 at 1064nm after approximately 1 week of transport over the tropical Atlantic. Based on published simulation studies we present an attempt to explain the spectral features of the depolarization ratio of irregularly shaped mineral dust particles, and conclude that most of the irregularly shaped coarse-mode dust particles (particles with diameters > 1μm) have sizes around 1.5-2μm. The SALTRACE results are also set into the context of the SAMUM-1 (Morocco, 2006) and SAMUM-2 (Cabo Verde, 2008) depolarization ratio studies. Again, only minor changes in the dust depolarization characteristics were observed on the way from the Saharan dust sources towards the Caribbean.
- ItemPolarization lidar: An extended three-signal calibration approach(Katlenburg-Lindau : Copernicus, 2019) Jimenez, Cristofer; Ansmann, Albert; Engelmann, Ronny; Haarig, Moritz; Schmidt, Jörg; Wandinger, UllaWe present a new formalism to calibrate a threesignal polarization lidar and to measure highly accurate height profiles of the volume linear depolarization ratios under realistic experimental conditions. The methodology considers elliptically polarized laser light, angular misalignment of the receiver unit with respect to the main polarization plane of the laser pulses, and cross talk among the receiver channels. A case study of a liquid-water cloud observation demonstrates the potential of the new technique. Long-term observations of the calibration parameters corroborate the robustness of the method and the long-term stability of the three-signal polarization lidar. A comparison with a second polarization lidar shows excellent agreement regarding the derived volume linear polarization ratios in different scenarios: A biomass burning smoke event throughout the troposphere and the lower stratosphere up to 16 km in height, a dust case, and also a cirrus cloud case. © Author(s) 2019.