scispace - formally typeset
Search or ask a question
Author

Jörg Schmidt

Bio: Jörg Schmidt is an academic researcher from Leibniz Association. The author has contributed to research in topics: Lidar & Aerosol. The author has an hindex of 10, co-authored 12 publications receiving 669 citations. Previous affiliations of Jörg Schmidt include Leibniz Institute for Neurobiology.
Topics: Lidar, Aerosol, Volcanic ash, Volcano, Sun photometer

Papers
More filters
Journal ArticleDOI
TL;DR: The optically thickest volcanic ash plume ever measured over Germany was monitored with multiwavelength Raman lidars and Sun photometer at Leipzig and Munich.
Abstract: [1] The optically thickest volcanic ash plume ever measured over Germany was monitored with multiwavelength Raman lidars and Sun photometer at Leipzig and Munich. When this ash layer, originating from the Eyjafjoll eruptions in southern Iceland, crossed Leipzig between 2.5 and 6 km height on 16 April 2010, the total 500 nm aerosol optical depth reached 1.0, and the ash–related optical depth was about 0.7. Volume light–extinction coefficients (40–75–minute mean values) measured over Leipzig and Munich at 355 and 532 nm reached values of 400–600 Mm−1 and ash mass concentrations were on the order of 1000 ± 350 μg/m3 in the center of the main ash layer. Extinction–to–backscatter ratios ranged from 55 ± 5 sr (Munich) to 60 ± 5 sr (Leipzig) in the main ash layer, and the particle linear depolarization ratio was close to 0.35 at both wavelengths. Rather low photometer–derived Angstrom exponents (500–1640 nm wavelength range) indicated the presence of a significant amount of large ash particles with diameters >20 μm.

178 citations

Journal ArticleDOI
TL;DR: In this article, a combined lidar-photometer method that permits the retrieval of vertical profiles of ash and non-ash (fine-mode) particle mass concentrations is presented.
Abstract: [1] A combined lidar-photometer method that permits the retrieval of vertical profiles of ash and non-ash (fine-mode) particle mass concentrations is presented. By using a polarization lidar, the contributions of non-ash and ash particles to total particle backscattering and extinction are separated. Sun photometer measurements of the ratio of particle volume concentration to particle optical thickness (AOT) for fine and coarse mode are then used to convert the non-ash and ash extinction coefficients into respective fine-mode and ash particle mass concentrations. The method is applied to European Aerosol Research Lidar Network (EARLINET) and Aerosol Robotic Network (AERONET) Sun photometer observations of volcanic aerosol layers at Cabauw, Netherlands, and Hamburg, Munich, and Leipzig, Germany, after the strong eruptions of the Icelandic Eyjafjallajokull volcano in April and May 2010. A consistent picture in terms of photometer-derived fine- and coarse-mode AOTs and lidar-derived non-ash and ash extinction profiles is found. The good agreement between the fine- to coarse-mode AOT ratio and non-ash to ash AOT ratio ( 15 μm.

169 citations

Journal ArticleDOI
TL;DR: In this article, the authors show the four-dimensional (4-D) distribution of the Eyjafjallajokull volcanic cloud in the troposphere over Europe as observed by EARLINET during the entire volcanic event (15 April-26 May 2010).
Abstract: . The eruption of the Icelandic volcano Eyjafjallajokull in April–May 2010 represents a "natural experiment" to study the impact of volcanic emissions on a continental scale. For the first time, quantitative data about the presence, altitude, and layering of the volcanic cloud, in conjunction with optical information, are available for most parts of Europe derived from the observations by the European Aerosol Research Lidar NETwork (EARLINET). Based on multi-wavelength Raman lidar systems, EARLINET is the only instrument worldwide that is able to provide dense time series of high-quality optical data to be used for aerosol typing and for the retrieval of particle microphysical properties as a function of altitude. In this work we show the four-dimensional (4-D) distribution of the Eyjafjallajokull volcanic cloud in the troposphere over Europe as observed by EARLINET during the entire volcanic event (15 April–26 May 2010). All optical properties directly measured (backscatter, extinction, and particle linear depolarization ratio) are stored in the EARLINET database available at http://www.earlinet.org . A specific relational database providing the volcanic mask over Europe, realized ad hoc for this specific event, has been developed and is available on request at http://www.earlinet.org . During the first days after the eruption, volcanic particles were detected over Central Europe within a wide range of altitudes, from the upper troposphere down to the local planetary boundary layer (PBL). After 19 April 2010, volcanic particles were detected over southern and south-eastern Europe. During the first half of May (5–15 May), material emitted by the Eyjafjallajokull volcano was detected over Spain and Portugal and then over the Mediterranean and the Balkans. The last observations of the event were recorded until 25 May in Central Europe and in the Eastern Mediterranean area. The 4-D distribution of volcanic aerosol layering and optical properties on European scale reported here provides an unprecedented data set for evaluating satellite data and aerosol dispersion models for this kind of volcanic events.

91 citations

Journal ArticleDOI
TL;DR: In this paper, a multi-wavelength aerosol Raman lidar was used to detect volcanic aerosol in the upper troposphere and lower stratosphere of the European Aerosol Research Lidar Network (EARLINET).
Abstract: [1] In the framework of regular European Aerosol Research Lidar Network (EARLINET) observations, aerosol layers have been monitored with a multiwavelength aerosol Raman lidar in the upper troposphere and lower stratosphere over Leipzig (51.4°N, 12.4°E), Germany, since the summer of 2008. The origins of these layers are eruptions of different volcanoes on the Aleutian Islands, Kamchatka, Alaska, and on the Kuril Islands. FLEXPART transport simulations show that the volcanic aerosol is advected from Alaska to central Europe within about 7 days. The aerosol layers typically occurred in the upper troposphere above 5 km height and in the lower stratosphere below 25 km height. The optical depths of the volcanic aerosol layers are mostly between 0.004 and 0.025 at 532 nm. The wavelength dependence of the backscatter coefficients and extinction coefficients indicate Angstrom exponents from 1.0–2.0. Lidar ratios in the stratosphere are found in the range from 30–60 sr (355 nm) and 30–45 sr (532 nm). The estimation of the effective radius, surface-area, and mass concentrations of a volcanic aerosol layer, observed well within the stratosphere at end of August 2009, reveals values of 0.1–0.2 μm, 5–10 μm2 cm−3, and 0.3–0.5 μg m−3, respectively.

77 citations

Journal ArticleDOI
TL;DR: In this paper, the influence of volcanic ash on heterogeneous ice nucleation in tropospheric clouds is investigated on the basis of 90 observed cloud cases, which were observed with polarization lidars at the two central-European EARLINET stations Leipzig (51.3°N, 12.4°E) and Maisach (48.2°E, 11.5°C) in volcanic aerosol layers which originated from the strong eruptions of the Icelandic Eyjafjallajokull volcano in April 2010.
Abstract: [1] The influence of volcanic ash on heterogeneous ice nucleation in tropospheric clouds is investigated on the basis of 90 observed cloud cases. The clouds were observed with polarization lidars at the two central-European EARLINET stations Leipzig (51.3°N, 12.4°E) and Maisach (48.2°N, 11.3°E, 25 km northwest of Munich), Germany, in volcanic aerosol layers which originated from the strong eruptions of the Icelandic Eyjafjallajokull volcano in April 2010. Case studies of evolving boundary layer cumuli and long-lasting free tropospheric cloud events with unusual behavior (mixed-phase cloud complex, cirrus deck) are discussed. A clear impact of ash is observed. The ice nuclei concentration derived from the lidar observations has been estimated to range from 2–20 per liter in the boundary layer and from 100–300 per liter at cirrus level. The statistical analysis based on the 90 evaluated cloud cases revealed that all observed cloud layers with cloud top temperatures of below −15°C contained ice. Typically (under non-volcanic aerosol conditions) such a high fraction of ice-containing clouds is not reached before temperatures decrease below −25°C over central Europe.

68 citations


Cited by
More filters
Journal ArticleDOI
TL;DR: Aerosol species which have been identified in the past as potentially important ice nuclei are introduced and their ice-nucleating ability when immersed in a supercooled droplet is addressed and the importance of ice nucleation by different aerosol types is estimated.
Abstract: The formation of ice particles in the Earth's atmosphere strongly affects the properties of clouds and their impact on climate. Despite the importance of ice formation in determining the properties of clouds, the Intergovernmental Panel on Climate Change (IPCC, 2007) was unable to assess the impact of atmospheric ice formation in their most recent report because our basic knowledge is insufficient. Part of the problem is the paucity of quantitative information on the ability of various atmospheric aerosol species to initiate ice formation. Here we review and assess the existing quantitative knowledge of ice nucleation by particles immersed within supercooled water droplets. We introduce aerosol species which have been identified in the past as potentially important ice nuclei and address their ice-nucleating ability when immersed in a supercooled droplet. We focus on mineral dusts, biological species (pollen, bacteria, fungal spores and plankton), carbonaceous combustion products and volcanic ash. In order to make a quantitative comparison we first introduce several ways of describing ice nucleation and then summarise the existing information according to the time-independent (singular) approximation. Using this approximation in combination with typical atmospheric loadings, we estimate the importance of ice nucleation by different aerosol types. According to these estimates we find that ice nucleation below about −15 °C is dominated by soot and mineral dusts. Above this temperature the only materials known to nucleate ice are biological, with quantitative data for other materials absent from the literature. We conclude with a summary of the challenges our community faces.

943 citations

Journal ArticleDOI
TL;DR: In this paper, new developments in identifying the heterogeneous freezing mechanisms, atmospheric relevance, uncertainties, and unknowns about ice nucleating particles (INPs) have been described, and the change in conventional wisdom regarding the requirements of INPs as new studies discover physical and chemical properties of these particles is explained.
Abstract: Ice particle formation in tropospheric clouds significantly changes cloud radiative and microphysical properties. Ice nucleation in the troposphere via homogeneous freezing occurs at temperatures lower than −38°C and relative humidity with respect to ice above 140%. In the absence of these conditions, ice formation can proceed via heterogeneous nucleation aided by aerosol particles known as ice nucleating particles (INPs). In this chapter, new developments in identifying the heterogeneous freezing mechanisms, atmospheric relevance, uncertainties, and unknowns about INPs are described. The change in conventional wisdom regarding the requirements of INPs as new studies discover physical and chemical properties of these particles is explained. INP sources and known reasons for their ice nucleating properties are presented. The need for more studies to systematically identify particle properties that facilitate ice nucleation is highlighted. The atmospheric relevance of long-range transport, aerosol a...

437 citations

Journal ArticleDOI
TL;DR: The European Aerosol Research Lidar Network (EARLINET) as mentioned in this paper was founded as a research project for establishing a quantitative, comprehensive, and statistically significant database for the horizontal, vertical, and tempo-ral distribution of aerosols on a continental scale.
Abstract: The European Aerosol Research Lidar Network, EARLINET, was founded in 2000 as a research project for establishing a quantitative, comprehensive, and statistically significant database for the horizontal, vertical, and tempo- ral distribution of aerosols on a continental scale. Since then EARLINET has continued to provide the most extensive col- lection of ground-based data for the aerosol vertical distribu- tion over Europe. This paper gives an overview of the network's main de- velopments since 2000 and introduces the dedicated EAR- LINET special issue, which reports on the present innova- tive and comprehensive technical solutions and scientific re- sults related to the use of advanced lidar remote sensing tech- niques for the study of aerosol properties as developed within the network in the last 13 years. Since 2000, EARLINET has developed greatly in terms of number of stations and spatial distribution: from 17 sta- tions in 10 countries in 2000 to 27 stations in 16 countries in 2013. EARLINET has developed greatly also in terms of technological advances with the spread of advanced multi- wavelength Raman lidar stations in Europe. The develop- ments for the quality assurance strategy, the optimization of instruments and data processing, and the dissemination of data have contributed to a significant improvement of the net- work towards a more sustainable observing system, with an increase in the observing capability and a reduction of oper- ational costs. Consequently, EARLINET data have already been ex- tensively used for many climatological studies, long-range transport events, Saharan dust outbreaks, plumes from vol- canic eruptions, and for model evaluation and satellite data validation and integration. Future plans are aimed at continuous measurements and near-real-time data delivery in close cooperation with other ground-based networks, such as in the ACTRIS (Aerosols, Clouds, and Trace gases Research InfraStructure Network) www.actris.net, and with the modeling and satellite commu- nity, linking the research community with the operational world, with the aim of establishing of the atmospheric part of the European component of the integrated global observ- ing system.

417 citations

Journal ArticleDOI
TL;DR: The 39-day long eruption at the summit of Eyjafjallajökull volcano in April–May 2010 was of modest size but ash was widely dispersed, combining data from ground surveys and remote sensing to show that the erupted material was 4.8±1.2·1011 kg.
Abstract: The 39-day long eruption at the summit of Eyjafjallajokull volcano in April–May 2010 was of modest size but ash was widely dispersed. By combining data from ground surveys and remote sensing we show that the erupted material was 4.8±1.2·1011 kg (benmoreite and trachyte, dense rock equivalent volume 0.18±0.05 km3). About 20% was lava and water-transported tephra, 80% was airborne tephra (bulk volume 0.27 km3) transported by 3–10 km high plumes. The airborne tephra was mostly fine ash (diameter <1000 µm). At least 7·1010 kg (70 Tg) was very fine ash (<28 µm), several times more than previously estimated via satellite retrievals. About 50% of the tephra fell in Iceland with the remainder carried towards south and east, detected over ~7 million km2 in Europe and the North Atlantic. Of order 1010 kg (2%) are considered to have been transported longer than 600–700 km with <108 kg (<0.02%) reaching mainland Europe.

351 citations

Journal ArticleDOI
TL;DR: In this article, an inversion scheme was used to estimate the volcanic ash source strength as a function of altitude and time, and the results showed that volcanic ash concentrations at some altitude in the atmosphere exceeded the limits for the "Normal" flying zone in up to 14 % (6-16 %), 2 % (1-3 %) and 7 % (4-11 %) of the European area.
Abstract: . The April–May, 2010 volcanic eruptions of Eyjafjallajokull, Iceland caused significant economic and social disruption in Europe whilst state of the art measurements and ash dispersion forecasts were heavily criticized by the aviation industry. Here we demonstrate for the first time that large improvements can be made in quantitative predictions of the fate of volcanic ash emissions, by using an inversion scheme that couples a priori source information and the output of a Lagrangian dispersion model with satellite data to estimate the volcanic ash source strength as a function of altitude and time. From the inversion, we obtain a total fine ash emission of the eruption of 8.3 ± 4.2 Tg for particles in the size range of 2.8–28 μm diameter. We evaluate the results of our model results with a posteriori ash emissions using independent ground-based, airborne and space-borne measurements both in case studies and statistically. Subsequently, we estimate the area over Europe affected by volcanic ash above certain concentration thresholds relevant for the aviation industry. We find that during three episodes in April and May, volcanic ash concentrations at some altitude in the atmosphere exceeded the limits for the "Normal" flying zone in up to 14 % (6–16 %), 2 % (1–3 %) and 7 % (4–11 %), respectively, of the European area. For a limit of 2 mg m−3 only two episodes with fractions of 1.5 % (0.2–2.8 %) and 0.9 % (0.1–1.6 %) occurred, while the current "No-Fly" zone criterion of 4 mg m−3 was rarely exceeded. Our results have important ramifications for determining air space closures and for real-time quantitative estimations of ash concentrations. Furthermore, the general nature of our method yields better constraints on the distribution and fate of volcanic ash in the Earth system.

346 citations