Browsing by Author "Althausen, Dietrich"
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- 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.
- ItemAerosol layer heights above Tajikistan during the CADEX campaign(Les Ulis : EDP Sciences, 2019) Hofer, Julian; Althausen, Dietrich; Abdullaev, Sabur F.; Nazarov, Bakhron I.; Makhmudov, Abduvosit N.; Baars, Holger; Engelmann, Ronny; Ansmann, AlbertMineral dust influences climate and weather by direct and indirect effects. Surrounded by dust sources, Central Asian countries are affected by atmospheric mineral dust on a regular basis. Climate change effects like glacier retreat and desertification are prevalent in Central Asia as well. Therefore, the role of dust in the climate system in Central Asia needs to be clarified and quantified. During the Central Asian Dust EXperiment (CADEX) first lidar observations in Tajikistan were conducted. Long-term vertically resolved aerosol measurements were performed with the multiwavelength polarization Raman lidar PollyXT from March 2015 to August 2016 in Dushanbe, Tajikistan. In this contribution, a climatology of the aerosol layer heights is presented, which was retrieved from the 18-month lidar measurements. Automatic detection based on backscatter coefficient thresholds were used to retrieve the aerosol layer heights and yield similar layer heights as manual layer height determination. The significant aerosol layer height has a maximum in summer and a minimum in winter. The highest layers occurred in spring, but in summer uppermost layer heights above 6 km AGL are frequent, too. © 2019 The Authors, published by EDP Sciences.
- ItemAerosol properties over Southeastern China from multi-wavelength Raman and depolarization lidar measurements(Les Ulis : EDP Sciences, 2016) Heese, Birgit; Althausen, Dietrich; Baars, Holger; Bohlmann, Stephanie; Deng, RuruA dataset of particle optical properties of highly polluted urban aerosol over the Pearl River Delta, Guangzhou, China is presented. The data were derived from multi-wavelengths Raman and depolarization lidar PollyXT and AERONET sun photometer measurements. The measurement campaign was conducted from Nov 2011 to June 2012. High aerosol optical depth was observed in the polluted atmosphere over this megacity, with a mean value of 0.54 ± 0.33 and a peak value of even 1.9. For the particle characterization the lidar ratio and the linear particle depolarization ratio, both at 532 nm, were used. The mean values of these properties are 48.0 sr ± 10.7 sr for the lidar ratio and 4%+-4% for the particle depolarization ratio, which means most depolarization measurements stayed below 10%. So far, most of these results indicate urban pollution particles mixed with particles arisen from biomass and industrial burning.
- ItemThe automated multiwavelength Raman polarization and water-vapor lidar PollyXT: The neXT generation(München : European Geopyhsical Union, 2016) Engelmann, Ronny; Kanitz, Thomas; Baars, Holger; Heese, Birgit; Althausen, Dietrich; Skupin, Annett; Wandinger, Ulla; Komppula, Mika; Stachlewska, Iwona S.; Amiridis, Vassilis; Marinou, Eleni; Mattis, Ina; Linné, Holger; Ansmann, AlbertThe atmospheric science community demands autonomous and quality-assured vertically resolved measurements of aerosol and cloud properties. For this purpose, a portable lidar called Polly was developed at TROPOS in 2003. The lidar system was continuously improved with gained experience from the EARLINET community, involvement in worldwide field campaigns, and international institute collaborations within the last 10 years. Here we present recent changes of the setup of the portable multiwavelength Raman and polarization lidar PollyXT and discuss the improved capabilities of the system by means of a case study. The latest system developments include an additional near-range receiver unit for Raman measurements of the backscatter and extinction coefficient down to 120 m above ground, a water-vapor channel, and channels for simultaneous measurements of the particle linear depolarization ratio at 355 and 532 nm. Quality improvements were achieved by systematically following the EARLINET guidelines and the international PollyNET quality assurance developments. A modified ship radar ensures measurements in agreement with air-traffic safety regulations and allows for 24∕7 monitoring of the atmospheric state with PollyXT.
- ItemCADEX and beyond: Installation of a new PollyXT site in Dushanbe(Les Ulis : EDP Sciences, 2019) Engelmann, Ronny; Hofer, Julian; Makhmudov, Abduvosit N.; Baars, Holger; Hanbuch, Karsten; Ansmann, Albert; Abdullaev, Sabur F.; Macke, Andreas; Althausen, DietrichDuring the 18-month Central Asian Dust Experiment we conducted continuous lidar measurements at the Physical Technical Institute of the Academy of Sciences of Tajikistan in Dushanbe between 2015 and 2016. Mineral dust plumes from various source regions have been observed and characterized in terms of their occurrence, and their optical and microphysical properties with the Raman lidar PollyXT. Currently a new container-based lidar system is constructed which will be installed for continuous long-term measurements in Dushanbe. © 2019 The Authors, published by EDP Sciences.
- ItemCalibration of Raman lidar water vapor profiles by means of AERONET photometer observations and GDAS meteorological data(München : European Geopyhsical Union, 2018) Dai, Guangyao; Althausen, Dietrich; Hofer, Julian; Engelmann, Ronny; Seifert, Patric; Bühl, Johannes; Mamouri, Rodanthi-Elisavet; Wu, Songhua; Ansmann, AlbertWe present a practical method to continuously calibrate Raman lidar observations of water vapor mixing ratio profiles. The water vapor profile measured with the multiwavelength polarization Raman lidar PollyXT is calibrated by means of co-located AErosol RObotic NETwork (AERONET) sun photometer observations and Global Data Assimilation System (GDAS) temperature and pressure profiles. This method is applied to lidar observations conducted during the Cyprus Cloud Aerosol and Rain Experiment (CyCARE) in Limassol, Cyprus. We use the GDAS temperature and pressure profiles to retrieve the water vapor density. In the next step, the precipitable water vapor from the lidar observations is used for the calibration of the lidar measurements with the sun photometer measurements. The retrieved calibrated water vapor mixing ratio from the lidar measurements has a relative uncertainty of 11 % in which the error is mainly caused by the error of the sun photometer measurements. During CyCARE, nine measurement cases with cloud-free and stable meteorological conditions are selected to calculate the precipitable water vapor from the lidar and the sun photometer observations. The ratio of these two precipitable water vapor values yields the water vapor calibration constant. The calibration constant for the PollyXT Raman lidar is 6.56 g kg−1 ± 0.72 g kg−1 (with a statistical uncertainty of 0.08 g kg−1 and an instrumental uncertainty of 0.72 g kg−1). To check the quality of the water vapor calibration, the water vapor mixing ratio profiles from the simultaneous nighttime observations with Raman lidar and Vaisala radiosonde sounding are compared. The correlation of the water vapor mixing ratios from these two instruments is determined by using all of the 19 simultaneous nighttime measurements during CyCARE. Excellent agreement with the slope of 1.01 and the R2 of 0.99 is found. One example is presented to demonstrate the full potential of a well-calibrated Raman lidar. The relative humidity profiles from lidar, GDAS (simulation) and radiosonde are compared, too. It is found that the combination of water vapor mixing ratio and GDAS temperature profiles allow us to derive relative humidity profiles with the relative uncertainty of 10–20 %.
- ItemCalifornian Wildfire Smoke Over Europe: A First Example of the Aerosol Observing Capabilities of Aeolus Compared to Ground‐Based 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 3–4 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 ESA’s wind lidar mission Aeolus. An exceptional high smoke-AOT >0.4 was measured, yielding to a mean mass concentration of 8 μg m−3. The 355 nm lidar ratio was moderate at around 40–50 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 Aeolus’ aerosol and cloud products are still preliminary and subject to ongoing algorithm improvements.
- ItemCentral Asian Dust Experiment (CADEX): Multiwavelength polarization Raman lidar observations in Tajikistan(Les Ulis : EDP Sciences, 2016) Hofer, Julian; Althausen, Dietrich; Abdullaev, Sabur F.; Engelmann, Ronny; Baars, HolgerFor the first time lidar measurements of vertical aerosol profiles are conducted in Tajikistan/Central Asia. These measurements just started on March 17th, 2015. They are performed within the Central Asian Dust Experiment (CADEX) in Dushanbe and they will last at least one year. The deployed system for these observations is an updated version of the multiwavelength polarization Raman lidar PollyXT. Vertical profiles of the backscatter coefficient, the extinction coefficient, and the particle depolarization ratio are measured by this instrument. A first and preliminary measurement example of an aerosol layer over Dushanbe is shown.
- ItemCharacterization of Saharan dust, marine aerosols and mixtures of biomass-burning aerosols and dust by means of multi-wavelength depolarization and Raman lidar measurements during SAMUM 2(Milton Park : Taylor & Francis, 2017) Groß, Silke; Tesche, Matthias; Freudenthaler, Volker; Toledano, Carlos; Wiegner, Matthias; Ansmann, Albert; Althausen, Dietrich; Seefeldner, MeinhardThe particle linear depolarization ratio δp of Saharan dust, marine aerosols and mixtures of biomass-burning aerosols from southern West Africa and Saharan dust was determined at three wavelengths with three lidar systems during the SAharan Mineral dUst experiMent 2 at the airport of Praia, Cape Verde, between 22 January and 9 February 2008. The lidar ratio Sp of these major types of tropospheric aerosols was analysed at two wavelengths. For Saharan dust, we find wavelength dependent mean particle linear depolarization ratios δp of 0.24–0.27 at 355 nm, 0.29–0.31 at 532 nm and 0.36–0.40 at 710 nm, and wavelength independent mean lidar ratios Sp of 48–70 sr. Mixtures of biomass-burning aerosols and dust show wavelength independent values of δp and Sp between 0.12–0.23 and 57–98 sr, respectively. The mean values of marine aerosols range independent of wavelength for δp from 0.01 to 0.03 and for Sp from 14 to 24 sr.
- ItemContinuous vertical aerosol profiling with a multi-wavelength Raman polarization lidar over the Pearl River Delta, China(Katlenburg-Lindau : EGU, 2017) Heese, Birgit; Baars, Holger; Bohlmann, Stephanie; Althausen, Dietrich; Deng, RuruA dataset of particle optical properties of the highly polluted atmosphere over the Pearl River Delta (PRD), Guangzhou, China, is presented in this paper. The data were derived from the measurements of a multiwavelength Raman and depolarization lidar PollyXT and a co-located AERONET sun photometer. The measurement campaign was conducted from November 2011 to mid-June 2012. These are the first Raman lidar measurements in the PRD that lasted for several months. A mean value of aerosol optical depth (AOD) of 0.54±0.33 was observed by the sun photometer at 500 nm in the polluted atmosphere over this megacity for the whole measurement period. The lidar profiles frequently show lofted aerosol layers, which reach altitudes of up to 2 to 3 km and, especially during the spring season, up to 5 km. These layers contain between 12 and 56% of the total AOD, with the highest values in spring. The aerosol types in these lofted layers are classified by their optical properties. The observed lidar ratio values range from 30 to 80 sr with a mean value of 48.0±10.7 sr at 532 nm. The linear particle depolarization ratio at 532 nm lies mostly below 5 %, with a mean value of 3.6±3.7 %. The majority of the Ångström exponents lie between 0.5 and 1.5, indicating a mixture of fine- and coarsemode aerosols. These results reveal that mostly urban pollution particles mixed with particles produced from biomass and industrial burning are present in the atmosphere above the Pearl River Delta. Trajectory analyses show that these pollution mixtures arise mainly from local and regional sources.
- ItemDepolarization ratio profiling at several wavelengths in pure Saharan dust during SAMUM 2006(Milton Park : Taylor & Francis, 2017) Freudenthaler, Volker; Esselborn, Michael; Wiegner, Matthias; Heese, Birgit; Tesche, Matthias; Ansmann, Albert; Müller, Detlef; Althausen, Dietrich; Wirth, Martin; Fix, Andreas; Ehret, Gerhard; Knippertz, Peter; Toledano, Carlos; Gasteiger, Josef; Garhammer, Markus; Seefeldner, MeinhardVertical profiles of the linear particle depolarization ratio of pure dust clouds were measured during the Saharan Mineral Dust Experiment (SAMUM) at Ouarzazate, Morocco (30.9◦N, –6.9◦E), close to source regions in May–June 2006, with four lidar systems at four wavelengths (355, 532, 710 and 1064 nm). The intercomparison of the lidar systems is accompanied by a discussion of the different calibration methods, including a new, advanced method, and a detailed error analysis. Over the whole SAMUM periode pure dust layers show a mean linear particle depolarization ratio at 532 nm of 0.31, in the range between 0.27 and 0.35, with a mean Ångström exponent (AE, 440–870 nm) of 0.18 (range 0.04–0.34) and still high mean linear particle depolarization ratio between 0.21 and 0.25 during periods with aerosol optical thickness less than 0.1, with a mean AE of 0.76 (range 0.65–1.00), which represents a negative correlation of the linear particle depolarization ratio with the AE. A slight decrease of the linear particle depolarization ratio with wavelength was found between 532 and 1064 nm from 0.31 ± 0.03 to 0.27 ± 0.04.
- ItemDifferences and Similarities of Central Asian, African, and Arctic Dust Composition from a Single Particle Perspective(Basel, Switzerland : MDPI AG, 2020) Kandler, Konrad; Schneiders, Kilian; Heuser, Johannes; Waza, Andebo; Aryasree, Sudharaj; Althausen, Dietrich; Hofer, Julian; Abdullaev, Sabur F.; Makhmudov, Abduvosit N.Mineral dust composition affects a multitude of processes in the atmosphere and adjacent compartments. Dust dry deposition was collected near source in northwest Africa, in Central Asia, and on Svalbard and at three locations of the African outflow regime. Samples were subjected to automated scanning electron microscopy with energy-dispersive X-ray analysis to obtain size and composition of 216,000 individual particles. Results show low temporal variation in estimated optical properties for each location, but considerable differences between the African, Central Asian, and Arctic regimes. No significant difference was found between the K-feldspar relative abundances, indicating comparable related ice-nucleation abilities. The mixing state between calcium and iron compounds was different for near source and transport regimes, potentially in part due to size sorting effects. As a result, in certain situations (high acid availability, limited time) atmospheric processing of the dust is expected to lead to less increased iron solubility for near-source dusts (in particular for Central Asian ones) than for transported ones (in particular of Sahelian origin). © 2020 by the authors. Licensee MDPI, Basel, Switzerland.
- ItemDoppler lidar studies of heat island effects on vertical mixing of aerosols during SAMUM-2(Milton Park : Taylor & Francis, 2017) Engelmann, Ronny; Ansmann, Albert; Horn, Stefan; Seifert, Patric; Althausen, Dietrich; Tesche, Matthias; Esselborn, Michael; Fruntke, Julia; Lieke, Kirsten; Freudenthaler, Volker; Gross, SilkeA wind Doppler lidar was deployed next to three aerosol lidars during the SAMUM–2 campaign on the main island of Cape Verde. The effects of the differential heating of the island and the surrounding ocean and the orographic impact of the capital island Santiago and the small island on its luv side, Maio, are investigated. Horizontal and vertical winds were measured in the disturbed maritime boundary layer and compared to local radiosoundings. Lidar measurements from the research aircraft Falcon and a 3-D Large Eddy Simulation (LES) model were used in addition to study the heating effects on the scale of the islands. Indications are found that these effects can widely control the downward mixing from greater heights to the surface of African aerosols, mainly Saharan dust and biomass-burning smoke, which were detected in a complex layering over the Cape Verde region.
- ItemDry versus wet marine particle optical properties: RH dependence of depolarization ratio, backscatter, and extinction from multiwavelength lidar measurements during SALTRACE(München : European Geopyhsical Union, 2017) Haarig, Moritz; Ansmann, Albert; Gasteiger, Josef; Kandler, Konrad; Althausen, Dietrich; Baars, Holger; Radenz, Martin; Farrell, David A.Triple-wavelength lidar observations of the depolarization ratio and the backscatter coefficient of marine aerosol as a function of relative humidity (RH) are presented with a 5min time resolution. The measurements were performed at Barbados (13°N, 59°W) during the Saharan Aerosol Long-range Transport and Aerosol-Cloud interaction Experiment (SALTRACE) winter campaign in February 2014. The phase transition from spherical sea salt particles to cubic-like sea salt crystals was observed with a polarization lidar. The radiosonde and water-vapor Raman lidar observations show a drop in RH below 50% in the marine aerosol layer simultaneously with a strong increase in particle linear depolarization ratio, which reaches values up to 0.12±0.08 (at 355nm), 0.15±0.03 (at 532nm), and 0.10±0.01 (at 1064nm). The lidar ratio (extinction-to-backscatter ratio) increased from 19 and 23sr for spherical sea salt particles to 27 and 25sr (at 355 and 532nm, respectively) for cubic-like particle ensembles. Furthermore the scattering enhancement due to hygroscopic growth of the marine aerosol particles under atmospheric conditions was measured. Extinction enhancement factors from 40 to 80% RH of 1.94±0.94 at 355nm, 3.70±1.14 at 532nm, and 5.37±1.66 at 1064nm were found. The enhanced depolarization ratios and lidar ratios were compared to modeling studies of cubic sea salt particles.
- ItemDust mobilization and transport in the northern Sahara during SAMUM 2006 - A meteorological overview(Milton Park : Taylor & Francis, 2017) Knippertz, Peter; Ansmann, Albert; Althausen, Dietrich; Müller, Detlef; Tesche, Matthias; Bierwirth, Eike; Dinter, Tilman; Müller, Thomas; Von Hoyningen-Huene, Wolfgang; Schepanski, Kerstin; Wendisch, Manfred; Heinold, Bernd; Kandler, Konrad; Petzold, Andreas; Tegen, InaThe SAMUM field campaign in southern Morocco in May/June 2006 provides valuable data to study the emission, and the horizontal and vertical transports of mineral dust in the Northern Sahara. Radiosonde and lidar observations show differential advection of air masses with different characteristics during stable nighttime conditions and up to 5-km deep vertical mixing in the strongly convective boundary layer during the day. Lagrangian and synoptic analyses of selected dust periods point to a topographic channel from western Tunisia to central Algeria as a dust source region. Significant emission events are related to cold surges from the Mediterranean in association with eastward passing upper-level waves and lee cyclogeneses south of the Atlas Mountains. Other relevant events are local emissions under a distinct cut-off low over northwestern Africa and gust fronts associated with dry thunderstorms over the Malian and Algerian Sahara. The latter are badly represented in analyses from the European Centre for Medium–Range Weather Forecasts and in a regional dust model, most likely due to problems with moist convective dynamics and a lack of observations in this region. This aspect needs further study. The meteorological source identification is consistent with estimates of optical and mineralogical properties of dust samples.
- 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; Muñoz 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 João; 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; Évora, 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%. © Author(s) 2019.
- ItemEarlinet validation of CATS L2 product(Les Ulis : EDP Sciences, 2018) Proestakis, Emmanouil; Amiridis, Vassilis; Kottas, Michael; Marinou, Eleni; Binietoglou, Ioannis; Ansmann, Albert; Wandinger, Ulla; Yorks, John; Nowottnick, Edward; Makhmudov, Abduvosit; Papayannis, Alexandros; Pietruczuk, Aleksander; Gialitaki, Anna; Apituley, Arnoud; Muñoz-Porcar, Constantino; Bortoli, Daniele; Dionisi, Davide; Althausen, Dietrich; Mamali, Dimitra; Balis, Dimitris; Nicolae, Doina; Tetoni, Eleni; Luigi Liberti, Gian; Baars, Holger; Stachlewska, Iwona S.; Voudouri, Kalliopi-Artemis; Mona, Lucia; Mylonaki, Maria; Rita Perrone, Maria; João Costa, Maria; Sicard, Michael; Papagiannopoulos, Nikolaos; Siomos, Nikolaos; Burlizzi, Pasquale; Engelmann, Ronny; Abdullaev, Sabur F.; Hofer, Julian; Pappalardo, Gelsomina; Nicolae, D.; Makoto, A.; Vassilis, A.; Balis, D.; Behrendt, A.; Comeron, A.; Gibert, F.; Landulfo, E.; McCormick, M.P.; Senff, C.; Veselovskii, I.; Wandinger, U.The Cloud-Aerosol Transport System (CATS) onboard the International Space Station (ISS), is a lidar system providing vertically resolved aerosol and cloud profiles since February 2015. In this study, the CATS aerosol product is validated against the aerosol profiles provided by the European Aerosol Research Lidar Network (EARLINET). This validation activity is based on collocated CATS-EARLINET measurements and the comparison of the particle backscatter coefficient at 1064nm.
- ItemEstimation of dust related ice nucleating particles in the atmosphere: Comparison of profiling and in-situ measurements(Les Ulis : EDP Sciences, 2019) Haarig, Moritz; Ansmann, Albert; Walser, Adrian; Baars, Holger; Urbanneck, Claudia; Weinzierl, Bernadett; Schöberl, Manuel; Dollner, Maximilian; Mamouri, Rodanthi; Althausen, DietrichVertical profiles of number concentrations of dust particles relevant for ice nucleation in clouds are derived from lidar measurements. The results are compared to coincidental airborne in-situ measurements of particle number and surface area concentrations in the dust layer. The observations were performed in long-range transported Saharan dust at Barbados and Asian dust at Cyprus. The Asian dust data analysis is ongoing. A comparison of Asian and Saharan dust will be given at the conference. Concentrations of ice nucleating particles in the order of 10 to 1000 per cm-3 in the dust layer are derived for a temperature of-25°C at Barbados. The method can be used to continuously monitor the concentration of ice nucleating dust particles vertically resolved from lidar measurements. © 2019 The Authors, published by EDP Sciences.
- 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 47g±g8, 50g±g5 and 69g±g14gsr and particle linear depolarization ratios of 0.242g±g0.024, 0.299g±g0.018 and 0.206g±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 49g±g4, 46g±g5 and 57g±g9gsr and the depolarization ratio of 0.174g±g0.041, 0.298g±g0.016 and 0.242g±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.
- ItemLong-term profiling of aerosol light extinction, particle mass, cloud condensation nuclei, and ice-nucleating particle concentration over Dushanbe, Tajikistan, in Central Asia(Katlenburg-Lindau : EGU, 2020) Hofer, Julian; Ansmann, Albert; Althausen, Dietrich; Engelmann, Ronny; Baars, Holger; Abdullaev, Sabur F.; Makhmudov, Abduvosit N.For the first time, continuous, vertically resolved long-term aerosol measurements were conducted with a state-of-the-art multiwavelength lidar over a Central Asian site. Such observations are urgently required in efforts to predict future climate and environmental conditions and to support spaceborne remote sensing (ground truth activities). The lidar observations were performed in the framework of the Central Asian Dust Experiment (CADEX) at Dushanbe, Tajikistan, from March 2015 to August 2016. An AERONET (AErosol RObotic NETwork) sun photometer was operated at the lidar field site. During the 18-month campaign, mixtures of continental aerosol pollution and mineral dust were frequently detected from ground to cirrus height level. Regional sources of dust and pollution as well as long-range transport of mineral dust mainly from Middle Eastern and the Saharan deserts determine the aerosol conditions over Tajikistan. In this study, we summarize our findings and present seasonally resolved statistics regarding aerosol layering (main aerosol layer depth, lofted layer occurrence); optical properties (aerosol and dust optical thicknesses at 500–532 nm, vertically resolved light-extinction coefficient at 532 nm); profiles of dust and non-dust mass concentrations and dust fraction; and profiles of particle parameters relevant for liquid water, mixed-phase cloud, and cirrus formation such as cloud condensation nuclei (CCN) and ice-nucleating particle (INP) concentrations. The main aerosol layer over Dushanbe typically reaches 4–5 km height in spring to autumn. Frequently lofted dust-containing aerosol layers were observed at heights from 5 to 10 km, indicating a sensitive potential of dust to influence cloud ice formation. Typical dust mass fractions were of the order of 60 %–80 %. A considerable fraction is thus anthropogenic pollution and biomass burning smoke. The highest aerosol pollution levels (in the relatively shallow winter boundary layer) occur during the winter months. The seasonal mean 500 nm AOT (aerosol optical thickness) ranges from 0.15 in winter to 0.36 in summer during the CADEX period (March 2015 to August 2016); DOTs (dust optical thicknesses) were usually below 0.2; seasonally mean particle extinction coefficients were of the order of 100–500 Mm−1 in the main aerosol layer during the summer half year and about 100–150 Mm−1 in winter but were mainly caused by anthropogenic haze. Accordingly, the highest dust mass concentrations occurred in the summer season (200–600 µg m−3) and the lowest during the winter months (20–50 µg m−3) in the main aerosol layer. In winter, the aerosol pollution mass concentrations were 20–50 µg m−3, while during the summer half year (spring to autumn), the mass concentration caused by urban haze and biomass burning smoke decreases to 10–20 µg m−3 in the lower troposphere. The CCN concentration levels are always controlled by aerosol pollution. The INP concentrations were found to be high enough in the middle and upper troposphere to significantly influence ice formation in mixed-phase and ice clouds during spring and summer seasons.
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