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- ItemTropospheric and stratospheric wildfire smoke profiling with lidar: mass, surface area, CCN, and INP retrieval(Katlenburg-Lindau : European Geosciences Union, 2021) Ansmann, Albert; Ohneiser, Kevin; Mamouri, Rodanthi-Elisavet; Knopf, Daniel A.; Veselovskii, Igor; Baars, Holger; Engelmann, Ronny; Foth, Andreas; Jimenez, Cristofer; Seifert, Patric; Barja, BorisWe present retrievals of tropospheric and stratospheric height profiles of particle mass, volume, surface area, and number concentrations in the case of wildfire smoke layers as well as estimates of smoke-related cloud condensation nuclei (CCN) and ice-nucleating particle (INP) concentrations from backscatter lidar measurements on the ground and in space. Conversion factors used to convert the optical measurements into microphysical properties play a central role in the data analysis, in addition to estimates of the smoke extinction-to-backscatter ratios required to obtain smoke extinction coefficients. The set of needed conversion parameters for wildfire smoke is derived from AERONET observations of major smoke events, e.g., in western Canada in August 2017, California in September 2020, and southeastern Australia in January-February 2020 as well as from AERONET long-term observations of smoke in the Amazon region, southern Africa, and Southeast Asia. The new smoke analysis scheme is applied to CALIPSO observations of tropospheric smoke plumes over the United States in September 2020 and to ground-based lidar observation in Punta Arenas, in southern Chile, in aged Australian smoke layers in the stratosphere in January 2020. These case studies show the potential of spaceborne and ground-based lidars to document large-scale and long-lasting wildfire smoke events in detail and thus to provide valuable information for climate, cloud, and air chemistry modeling efforts performed to investigate the role of wildfire smoke in the atmospheric system. © 2021 Albert Ansmann et al.
- ItemThe Pagami Creek smoke plume after long-range transport to the upper troposphere over Europe – Aerosol properties and black carbon mixing state(München : European Geopyhsical Union, 2014) Dahlkötter, F.; Gysel, M.; Sauer, D.; Minikin, A.; Baumann, R.; Seifert, P.; Ansmann, A.; Fromm, M.; Voigt, C.; Weinzierl, B.During the CONCERT 2011 field experiment with the DLR research aircraft Falcon, an enhanced aerosol layer with particle linear depolarization ratios of 6–8% at 532 nm was observed at altitudes above 10 km over northeast Germany on 16 September 2011. Dispersion simulations with HYSPILT suggest that the elevated aerosol layer originated from the Pagami Creek forest fire in Minnesota, USA, which caused pyro-convective uplift of particles and gases. The 3–4 day-old smoke plume had high total refractory black carbon (rBC) mass concentrations of 0.03–0.35 μg m−3 at standard temperature and pressure (STP) with rBC mass equivalent diameter predominantly smaller than 130 nm. Assuming a core-shell particle structure, the BC cores exhibit very thick (median: 105–136 nm) BC-free coatings. A large fraction of the BC-containing particles disintegrated into a BC-free fragment and a BC fragment while passing through the laser beam of the Single Particle Soot Photometer (SP2). In this study, the disintegration is a result of very thick coatings around the BC cores. This is in contrast to a previous study in a forest-fire plume, where it was hypothesized to be a result of BC cores being attached to a BC-free particle. For the high-altitude forest-fire aerosol layer observed in this study, increased mass specific light-absorption cross sections of BC can be expected due to the very thick coatings around the BC cores, while this would not be the case for the attached-type morphology. We estimate the BC mass import from the Pagami Creek forest fire into the upper troposphere/lower stratosphere (UTLS) region (best estimate: 25 Mg rBC). A comparison to black carbon emission rates from aviation underlines the importance of pyro-convection on the BC load in the UTLS region. Our study provides detailed information on the microphysics and the mixing state of BC in the forest-fire aerosol layer in the upper troposphere that can be used to better understand and investigate the radiative impact of such upper tropospheric aerosol layers.
- 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.
- ItemDepolarization and lidar ratios at 355, 532, and 1064 nm and microphysical properties of aged tropospheric and stratospheric Canadian wildfire smoke(Göttingen : Copernicus GmbH, 2018) Haarig, M.; Ansmann, A.; Baars, H.; Jimenez, C.; Veselovskii, I.; Engelmann, R.; Althausen, D.We present spectrally resolved optical and microphysical properties of western Canadian wildfire smoke observed in a tropospheric layer from 5-6.5 km height and in a stratospheric layer from 15-16 km height during a recordbreaking smoke event on 22 August 2017. Three polarization/ Raman lidars were run at the European Aerosol Research Lidar Network (EARLINET) station of Leipzig, Germany, after sunset on 22 August. For the first time, the linear depolarization ratio and extinction-to-backscatter ratio (lidar ratio) of aged smoke particles were measured at all three important lidar wavelengths of 355, 532, and 1064 nm. Very different particle depolarization ratios were found in the troposphere and in the stratosphere. The obviously compact and spherical tropospheric smoke particles caused almost no depolarization of backscattered laser radiation at all three wavelengths ( < 3 %), whereas the dry irregularly shaped soot particles in the stratosphere lead to high depolarization ratios of 22% at 355 nm and 18% at 532 nm and a comparably low value of 4% at 1064 nm. The lidar ratios were 40- 45 sr (355 nm), 65-80 sr (532 nm), and 80-95 sr (1064 nm) in both the tropospheric and stratospheric smoke layers indicating similar scattering and absorption properties. The strong wavelength dependence of the stratospheric depolarization ratio was probably caused by the absence of a particle coarse mode (particle mode consisting of particles with radius > 500nm). The stratospheric smoke particles formed a pronounced accumulation mode (in terms of particle volume or mass) centered at a particle radius of 350-400 nm. The effective particle radius was 0.32 μm. The tropospheric smoke particles were much smaller (effective radius of 0.17 μm). Mass concentrations were of the order of 5.5 μgm-3 (tropospheric layer) and 40 μgm-3 (stratospheric layer) in the night of 22 August 2017. The single scattering albedo of the stratospheric particles was estimated to be 0.74, 0.8, and 0.83 at 355, 532, and 1064 nm, respectively.
- 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).