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- ItemOzone depletion in the Arctic and Antarctic stratosphere induced by wildfire smoke(Katlenburg-Lindau : EGU, 2022) Ansmann, Albert; Ohneiser, Kevin; Chudnovsky, Alexandra; Knopf, Daniel A.; Eloranta, Edwin W.; Villanueva, Diego; Seifert, Patric; Radenz, Martin; Barja, Boris; Zamorano, FĆ©lix; Jimenez, Cristofer; Engelmann, Ronny; Baars, Holger; Griesche, Hannes; Hofer, Julian; Althausen, Dietrich; Wandinger, UllaA record-breaking stratospheric ozone loss was observed over the Arctic and Antarctica in 2020. Strong ozone depletion occurred over Antarctica in 2021 as well. The ozone holes developed in smoke-polluted air. In this article, the impact of Siberian and Australian wildfire smoke (dominated by organic aerosol) on the extraordinarily strong ozone reduction is discussed. The study is based on aerosol lidar observations in the North Pole region (October 2019-May 2020) and over Punta Arenas in southern Chile at 53.2Ā°S (January 2020-November 2021) as well as on respective NDACC (Network for the Detection of Atmospheric Composition Change) ozone profile observations in the Arctic (Ny-Ć lesund) and Antarctica (Neumayer and South Pole stations) in 2020 and 2021. We present a conceptual approach on how the smoke may have influenced the formation of polar stratospheric clouds (PSCs), which are of key importance in the ozone-depleting processes. The main results are as follows: (a) the direct impact of wildfire smoke below the PSC height range (at 10-12 km) on ozone reduction seems to be similar to well-known volcanic sulfate aerosol effects. At heights of 10-12 km, smoke particle surface area (SA) concentrations of 5-7 Ī¼m2 cm-3 (Antarctica, spring 2021) and 6-10 Ī¼m2 cm-3 (Arctic, spring 2020) were correlated with an ozone reduction in terms of ozone partial pressure of 0.4-1.2 mPa (about 30 % further ozone reduction over Antarctica) and of 2-3.5 mPa (Arctic, 20 %-30 % reduction with respect to the long-term springtime mean). (b) Within the PSC height range, we found indications that smoke was able to slightly increase the PSC particle number and surface area concentration. In particular, a smoke-related additional ozone loss of 1-2 mPa (10 %-20 % contribution to the total ozone loss over Antarctica) was observed in the 14-23 km PSC height range in September-October 2020 and 2021. Smoke particle number concentrations ranged from 10 to 100 cm-3 and were about a factor of 10 (in 2020) and 5 (in 2021) above the stratospheric aerosol background level. Satellite observations indicated an additional mean column ozone loss (deviation from the long-term mean) of 26-30 Dobson units (9 %-10 %, September 2020, 2021) and 52-57 Dobson units (17 %-20 %, October 2020, 2021) in the smoke-polluted latitudinal Antarctic belt from 70-80Ā°S. Copyright:
- ItemWildfire smoke, Arctic haze, and aerosol effects on mixed-phase and cirrus clouds over the North Pole region during MOSAiC: an introduction(Katlenburg-Lindau : European Geosciences Union, 2021) Engelmann, Ronny; Ansmann, Albert; Ohneiser, Kevin; Griesche, Hannes; Radenz, Martin; Hofer, Julian; Althausen, Dietrich; Dahlke, Sandro; Maturilli, Marion; Veselovskii, Igor; Jimenez, Cristofer; Wiesen, Robert; Baars, Holger; BĆ¼hl, Johannes; Gebauer, Henriette; Haarig, Moritz; Seifert, Patric; Wandinger, Ulla; Macke, AndreasAn advanced multiwavelength polarization Raman lidar was operated aboard the icebreaker Polarstern during the MOSAiC (Multidisciplinary drifting Observatory for the Study of Arctic Climate) expedition to continuously monitor aerosol and cloud layers in the central Arctic up to 30gkm height. The expedition lasted from September 2019 to October 2020 and measurements were mostly taken between 85 and 88.5ggN. The lidar was integrated into a complex remote-sensing infrastructure aboard the Polarstern. In this article, novel lidar techniques, innovative concepts to study aerosol-cloud interaction in the Arctic, and unique MOSAiC findings will be presented. The highlight of the lidar measurements was the detection of a 10gkm deep wildfire smoke layer over the North Pole region between 7-8gkm and 17-18gkm height with an aerosol optical thickness (AOT) at 532gnm of around 0.1 (in October-November 2019) and 0.05 from December to March. The dual-wavelength Raman lidar technique allowed us to unambiguously identify smoke as the dominating aerosol type in the aerosol layer in the upper troposphere and lower stratosphere (UTLS). An additional contribution to the 532gnm AOT by volcanic sulfate aerosol (Raikoke eruption) was estimated to always be lower than 15g%. The optical and microphysical properties of the UTLS smoke layer are presented in an accompanying paper . This smoke event offered the unique opportunity to study the influence of organic aerosol particles (serving as ice-nucleating particles, INPs) on cirrus formation in the upper troposphere. An example of a closure study is presented to explain our concept of investigating aerosol-cloud interaction in this field. The smoke particles were obviously able to control the evolution of the cirrus system and caused low ice crystal number concentration. After the discussion of two typical Arctic haze events, we present a case study of the evolution of a long-lasting mixed-phase cloud layer embedded in Arctic haze in the free troposphere. The recently introduced dual-field-of-view polarization lidar technique was applied, for the first time, to mixed-phase cloud observations in order to determine the microphysical properties of the water droplets. The mixed-phase cloud closure experiment (based on combined lidar and radar observations) indicated that the observed aerosol levels controlled the number concentrations of nucleated droplets and ice crystals.
- ItemEARLINET evaluation of the CATS Level 2 aerosol backscatter coefficient product(Katlenburg-Lindau : EGU, 2019) Proestakis, Emmanouil; Amiridis, Vassilis; Marinou, Eleni; Binietoglou, Ioannis; Ansmann, Albert; Wandinger, Ulla; Hofer, Julian; Yorks, John; Nowottnick, Edward; Makhmudov, Abduvosit; Papayannis, Alexandros; Pietruczuk, Aleksander; Gialitaki, Anna; Apituley, Arnoud; Szkop, Artur; MuƱoz Porcar, Constantino; Bortoli, Daniele; Dionisi, Davide; Althausen, Dietrich; Mamali, Dimitra; Balis, Dimitris; Nicolae, Doina; Tetoni, Eleni; Liberti, Gian Luigi; Baars, Holger; Mattis, Ina; Stachlewska, Iwona Sylwia; Voudouri, Kalliopi Artemis; Mona, Lucia; Mylonaki, Maria; Perrone, Maria Rita; Costa, Maria JoĆ£o; Sicard, Michael; Papagiannopoulos, Nikolaos; Siomos, Nikolaos; Burlizzi, Pasquale; Pauly, Rebecca; Engelmann, Ronny; Abdullaev, Sabur; Pappalardo, GelsominaWe present the evaluation activity of the European Aerosol Research Lidar Network (EARLINET) for the quantitative assessment of the Level 2 aerosol backscatter coefficient product derived by the Cloud-Aerosol Transport System (CATS) aboard the International Space Station (ISS; Rodier et al., 2015). The study employs correlative CATS and EARLINET backscatter measurements within a 50km distance between the ground station and the ISS overpass and as close in time as possible, typically with the starting time or stopping time of the EARLINET performed measurement time window within 90min of the ISS overpass, for the period from February 2015 to September 2016. The results demonstrate the good agreement of the CATS Level 2 backscatter coefficient and EARLINET. Three ISS overpasses close to the EARLINET stations of Leipzig, Germany; Ćvora, Portugal; and Dushanbe, Tajikistan, are analyzed here to demonstrate the performance of the CATS lidar system under different conditions. The results show that under cloud-free, relative homogeneous aerosol conditions, CATS is in good agreement with EARLINET, independent of daytime and nighttime conditions. CATS low negative biases are observed, partially attributed to the deficiency of lidar systems to detect tenuous aerosol layers of backscatter signal below the minimum detection thresholds; these are biases which may lead to systematic deviations and slight underestimations of the total aerosol optical depth (AOD) in climate studies. In addition, CATS misclassification of aerosol layers as clouds, and vice versa, in cases of coexistent and/or adjacent aerosol and cloud features, occasionally leads to non-representative, unrealistic, and cloud-contaminated aerosol profiles. Regarding solar illumination conditions, low negative biases in CATS backscatter coefficient profiles, of the order of 6.1%, indicate the good nighttime performance of CATS. During daytime, a reduced signal-to-noise ratio by solar background illumination prevents retrievals of weakly scattering atmospheric layers that would otherwise be detectable during nighttime, leading to higher negative biases, of the order of 22.3%. Ā© Author(s) 2019.
- ItemFirst triple-wavelength lidar observations of depolarization and extinction-to-backscatter ratios of Saharan dus(Katlenburg-Lindau : EGU, 2022) Haarig, Moritz; Ansmann, Albert; Engelmann, Ronny; Baars, Holger; Toledano, Carlos; Torres, Benjamin; Althausen, Dietrich; Radenz, Martin; Wandinger, UllaTwo layers of Saharan dust observed over Leipzig, Germany, in February and March 2021 were used to provide the first-ever lidar measurements of the dust lidar ratio (extinction-to-backscatter ratio) and linear depolarization ratio at all three classical lidar wavelengths (355, 532 and 1064gnm). The pure-dust conditions during the first event exhibit lidar ratios of 47gĀ±g8, 50gĀ±g5 and 69gĀ±g14gsr and particle linear depolarization ratios of 0.242gĀ±g0.024, 0.299gĀ±g0.018 and 0.206gĀ±g0.010 at wavelengths of 355, 532 and 1064gnm, respectively. The second, slightly polluted-dust case shows a similar spectral behavior of the lidar and depolarization ratio with values of the lidar ratio of 49gĀ±g4, 46gĀ±g5 and 57gĀ±g9gsr and the depolarization ratio of 0.174gĀ±g0.041, 0.298gĀ±g0.016 and 0.242gĀ±g0.007 at 355, 532 and 1064gnm, respectively. The results were compared with Aerosol Robotic Network (AERONET) version 3 (v3) inversion solutions and the Generalized Retrieval of Aerosol and Surface Properties (GRASP) at six and seven wavelengths. Both retrieval schemes make use of a spheroid shape model for mineral dust. The spectral slope of the lidar ratio from 532 to 1064gnm could be well reproduced by the AERONET and GRASP retrieval schemes. Higher lidar ratios in the UV were retrieved by AERONET and GRASP. The enhancement was probably caused by the influence of fine-mode pollution particles in the boundary layer which are included in the columnar photometer measurements. Significant differences between the measured and retrieved wavelength dependence of the particle linear depolarization ratio were found. The potential sources for these uncertainties are discussed.
- ItemThe unprecedented 2017ā2018 stratospheric smoke event: decay phase and aerosol properties observed with the EARLINET(Katlenburg-Lindau : EGU, 2019) Baars, Holger; Ansmann, Albert; Ohneiser, Kevin; Haarig, Moritz; Engelmann, Ronny; Althausen, Dietrich; Hanssen, Ingrid; Gausa, Michael; Pietruczuk, Aleksander; Szkop, Artur; Stachlewska, Iwona S.; Wang, Dongxiang; Reichardt, Jens; Skupin, Annett; Mattis, Ina; Trickl, Thomas; Vogelmann, Hannes; Navas-GuzmĆ”n, Francisco; Haefele, Alexander; Acheson, Karen; Ruth, Albert A.; Tatarov, Boyan; MĆ¼ller, Detlef; Hu, Qiaoyun; Podvin, Thierry; Goloub, Philippe; Veselovskii, Igor; Pietras, Christophe; Haeffelin, Martial; FrĆ©ville, Patrick; Sicard, MichaĆ«l; ComerĆ³n, Adolfo; GarcĆa, Alfonso Javier FernĆ”ndez; Molero MenĆ©ndez, Francisco; CĆ³rdoba-Jabonero, Carmen; Guerrero-Rascado, Juan Luis; Alados-Arboledas, Lucas; Bortoli, Daniele; Costa, Maria JoĆ£o; Dionisi, Davide; Liberti, Gian Luigi; Wang, Xuan; Sannino, Alessia; Papagiannopoulos, Nikolaos; Boselli, Antonella; Mona, Lucia; DāAmico, Guiseppe; Romano, Salvatore; Perrone, Maria Rita; Belegante, Livio; Nicolae, Doina; Grigorov, Ivan; Gialitaki, Anna; Amiridis, Vassilis; Soupiona, Ourania; Papayannis, Alexandros; Mamouri, Rodanthi-Elisaveth; Nisantzi, Argyro; Heese, Birgit; Hofer, Julian; Schechner, Yoav Y.; Wandinger, Ulla; Pappalardo, GelsominaSix months of stratospheric aerosol observations with the European Aerosol Research Lidar Network (EARLINET) from August 2017 to January 2018 are presented. The decay phase of an unprecedented, record-breaking stratospheric perturbation caused by wildfire smoke is reported and discussed in terms of geometrical, optical, and microphysical aerosol properties. Enormous amounts of smoke were injected into the upper troposphere and lower stratosphere over fire areas in western Canada on 12 August 2017 during strong thunderstormāpyrocumulonimbus activity. The stratospheric fire plumes spread over the entire Northern Hemisphere in the following weeks and months. Twenty-eight European lidar stations from northern Norway to southern Portugal and the eastern Mediterranean monitored the strong stratospheric perturbation on a continental scale. The main smoke layer (over central, western, southern, and eastern Europe) was found at heights between 15 and 20ākm since September 2017 (about 2 weeks after entering the stratosphere). Thin layers of smoke were detected at heights of up to 22ā23ākm. The stratospheric aerosol optical thickness at 532ānm decreased from values >ā0.25 on 21ā23 August 2017 to 0.005ā0.03 until 5ā10 September and was mainly 0.003ā0.004 from October to December 2017 and thus was still significantly above the stratospheric background (0.001ā0.002). Stratospheric particle extinction coefficients (532ānm) were as high as 50ā200āMmā1 until the beginning of September and on the order of 1āMmā1 (0.5ā5āMmā1) from October 2017 until the end of January 2018. The corresponding layer mean particle mass concentration was on the order of 0.05ā0.5āĀµgāmā3 over these months. Soot particles (light-absorbing carbonaceous particles) are efficient ice-nucleating particles (INPs) at upper tropospheric (cirrus) temperatures and available to influence cirrus formation when entering the tropopause from above. We estimated INP concentrations of 50ā500āLā1 until the first days in September and afterwards 5ā50āLā1 until the end of the year 2017 in the lower stratosphere for typical cirrus formation temperatures of ā55āāC and an ice supersaturation level of 1.15. The measured profiles of the particle linear depolarization ratio indicated a predominance of nonspherical smoke particles. The 532ānm depolarization ratio decreased slowly with time in the main smoke layer from values of 0.15ā0.25 (AugustāSeptember) to values of 0.05ā0.10 (OctoberāNovember) and <ā0.05 (DecemberāJanuary). The decrease of the depolarization ratio is consistent with aging of the smoke particles, growing of a coating around the solid black carbon core (aggregates), and thus change of the shape towards a spherical form. We found ascending aerosol layer features over the most southern European stations, especially over the eastern Mediterranean at 32ā35āāN, that ascended from heights of about 18ā19 to 22ā23ākm from the beginning of October to the beginning of December 2017 (about 2ākm per month). We discuss several transport and lifting mechanisms that may have had an impact on the found aerosol layering structures.
- ItemOptical properties of Central Asian aerosol relevant for spaceborne lidar applications and aerosol typing at 355 and 532nm(Katlenburg-Lindau : EGU, 2020) Hofer, Julian; Ansmann, Albert; Althausen, Dietrich; Engelmann, Ronny; Baars, Holger; Fomba, Khanneh Wadinga; Wandinger, Ulla; Abdullaev, Sabur F.; Makhmudov, Abduvosit N.For the first time, a dense data set of particle extinction-to-backscatter ratios (lidar ratios), linear depolarization ratios, and backscatter- and extinction-related Ć ngstrƶm exponents for a Central Asian site are presented. The observations were performed with a continuously running multiwavelength polarization Raman lidar at Dushanbe, Tajikistan, during an 18-month campaign (March 2015 to August 2016). The presented seasonally resolved observations fill an important gap in the database of aerosol optical properties used in aerosol typing efforts with spaceborne lidars and ground-based lidar networks. Lidar ratios and depolarization ratios are also basic input parameters in spaceborne lidar data analyses and in efforts to harmonize long-term observations with different space lidar systems operated at either 355 or 532ānm. As a general result, the found optical properties reflect the large range of occurring aerosol mixtures consisting of long-range-transported dust (from the Middle East and the Sahara), regional desert, soil, and salt dust, and anthropogenic pollution. The full range from highly polluted to pure dust situations could be observed. Typical dust depolarization ratios of 0.23ā0.29 (355ānm) and 0.30ā0.35 (532ānm) were observed. In contrast, comparably low lidar ratios were found. Dust lidar ratios at 532ānm accumulated around 35ā40āsr and were even lower for regional background dust conditions (20ā30āsr). Detailed correlation studies (e.g., lidar ratio vs. depolarization ratios, Ć ngstrƶm exponent vs. lidar ratio and vs. depolarization ratio) are presented to illuminate the complex relationships between the observed optical properties and to identify the contributions of anthropogenic haze, dust, and background aerosol to the overall aerosol mixtures found within the 18-month campaign. The observation of 532ānm lidar ratios (<25āsr) and depolarization ratios (around 15ā%ā20ā%) in layers with very low particle extinction coefficient (<30āsr) suggests that direct emission and emission of resuspended salt dust (initially originated from numerous desiccating lakes and the Aralkum desert) have a sensitive impact on the aerosol background optical properties over Dushanbe.
- ItemCalifornian Wildfire Smoke Over Europe: A First Example of the Aerosol Observing Capabilities of Aeolus Compared to GroundāBased Lidar(Hoboken, NJ : Wiley, 2021) Baars, Holger; Radenz, Martin; Floutsi, Athena Augusta; Engelmann, Ronny; Althausen, Dietrich; Heese, Birgit; Ansmann, Albert; Flament, Thomas; Dabas, Alain; Trapon, Dimitri; Reitebuch, Oliver; Bley, Sebastian; Wandinger, UllaIn September 2020, extremely strong wildfires in the western United States of America (i.e., mainly in California) produced large amounts of smoke, which was lifted into the free troposphere. These biomass-burning-aerosol (BBA) layers were transported from the US west coast toward central Europe within 3ā4 days turning the sky milky and receiving high media attention. The present study characterizes this pronounced smoke plume above Leipzig, Germany, using a ground-based multiwavelength-Raman-polarization lidar and the aerosol/cloud product of ESAās wind lidar mission Aeolus. An exceptional high smoke-AOT >0.4 was measured, yielding to a mean mass concentration of 8 Ī¼g mā3. The 355 nm lidar ratio was moderate at around 40ā50 sr. The Aeolus-derived backscatter, extinction and lidar ratio profiles agree well with the observations of the ground-based lidar PollyXT considering the fact that Aeolusā aerosol and cloud products are still preliminary and subject to ongoing algorithm improvements.