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Prof. Dr. Andreas Macke
Leibniz Institute for Tropospheric Research, Leipzig, Germany

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0 Light Scattering
0 cloud remote sensing
0 Atmospheric particles
0 3D radiative transfer
0 Cloud radiative forcing

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Light Scattering
3D radiative transfer

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Research article
Published: 28 July 2021 in Atmospheric Measurement Techniques
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The modification of an existing cloud property retrieval scheme for the Spinning Enhanced Visible and Infrared Imager (SEVIRI) instrument on board the geostationary Meteosat satellites is described to utilize its high-resolution visible (HRV) channel for increasing the spatial resolution of its physical outputs. This results in products with a nadir spatial resolution of 1×1 km2 compared to the standard 3×3 km2 resolution offered by the narrowband channels. This improvement thus greatly reduces the resolution gap between current geostationary and polar-orbiting meteorological satellite imagers. In the first processing step, cloudiness is determined from the HRV observations by a threshold-based cloud masking algorithm. Subsequently, a linear model that links the 0.6 µm, 0.8 µm, and HRV reflectances provides a physical constraint to incorporate the spatial high-frequency component of the HRV observations into the retrieval of cloud optical depth. The implementation of the method is described, including the ancillary datasets used. It is demonstrated that the omission of high-frequency variations in the cloud-absorbing 1.6 µm channel results in comparatively large uncertainties in the retrieved cloud effective radius, likely due to the mismatch in channel resolutions. A newly developed downscaling scheme for the 1.6 µm reflectance is therefore applied to mitigate the effects of this scale mismatch. Benefits of the increased spatial resolution of the resulting SEVIRI products are demonstrated for three example applications: (i) for a convective cloud field, it is shown that significantly better agreement between the distributions of cloud optical depth retrieved from SEVIRI and from collocated MODIS observations is achieved. (ii) The temporal evolution of cloud properties for a growing convective storm at standard and HRV spatial resolutions are compared, illustrating an improved contrast in growth signatures resulting from the use of the HRV channel. (iii) An example of surface solar irradiance, determined from the retrieved cloud properties, is shown, for which the HRV channel helps to better capture the large spatiotemporal variability induced by convective clouds. These results suggest that incorporating the HRV channel into the retrieval has potential for improving Meteosat-based cloud products for several application domains.

ACS Style

Hartwig Deneke; Carola Barrientos-Velasco; Sebastian Bley; Anja Hünerbein; Stephan Lenk; Andreas Macke; Jan Fokke Meirink; Marion Schroedter-Homscheidt; Fabian Senf; Ping Wang; Frank Werner; Jonas Witthuhn. Increasing the spatial resolution of cloud property retrievals from Meteosat SEVIRI by use of its high-resolution visible channel: implementation and examples. Atmospheric Measurement Techniques 2021, 14, 5107 -5126.

AMA Style

Hartwig Deneke, Carola Barrientos-Velasco, Sebastian Bley, Anja Hünerbein, Stephan Lenk, Andreas Macke, Jan Fokke Meirink, Marion Schroedter-Homscheidt, Fabian Senf, Ping Wang, Frank Werner, Jonas Witthuhn. Increasing the spatial resolution of cloud property retrievals from Meteosat SEVIRI by use of its high-resolution visible channel: implementation and examples. Atmospheric Measurement Techniques. 2021; 14 (7):5107-5126.

Chicago/Turabian Style

Hartwig Deneke; Carola Barrientos-Velasco; Sebastian Bley; Anja Hünerbein; Stephan Lenk; Andreas Macke; Jan Fokke Meirink; Marion Schroedter-Homscheidt; Fabian Senf; Ping Wang; Frank Werner; Jonas Witthuhn. 2021. "Increasing the spatial resolution of cloud property retrievals from Meteosat SEVIRI by use of its high-resolution visible channel: implementation and examples." Atmospheric Measurement Techniques 14, no. 7: 5107-5126.

Journal article
Published: 14 July 2021 in Sustainability
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Community-based participatory research initiatives such as “hackAir”, “luftdaten.info”, “senseBox”, “CAPTOR”, “CurieuzeNeuzen Vlaanderen”, “communityAQ”, and “Healthy Air, Healthier Children” campaign among many others for mitigating short-lived climate pollutants (SLCPs) and improving air quality have reported progressive knowledge transfer results. These research initiatives provide the research community with the practical four-element state-of-the-art method for citizen science. For the preparation-, measurements-, data analysis-, and scientific support-elements that collectively present the novel knowledge transfer method, the Luft-Leipzig project results are presented. This research contributes to science by formulating a novel method for SLCP mitigation projects that employ citizen scientists. The Luft-Leipzig project results are presented to validate the four-element state-of-the-art method. The method is recommended for knowledge transfer purposes beyond the scope of mitigating short-lived climate pollutants (SLCPs) and improving air quality.

ACS Style

Liina Tõnisson; Jens Voigtländer; Michael Weger; Denise Assmann; Ralf Käthner; Bernd Heinold; Andreas Macke. Knowledge Transfer with Citizen Science: Luft-Leipzig Case Study. Sustainability 2021, 13, 7855 .

AMA Style

Liina Tõnisson, Jens Voigtländer, Michael Weger, Denise Assmann, Ralf Käthner, Bernd Heinold, Andreas Macke. Knowledge Transfer with Citizen Science: Luft-Leipzig Case Study. Sustainability. 2021; 13 (14):7855.

Chicago/Turabian Style

Liina Tõnisson; Jens Voigtländer; Michael Weger; Denise Assmann; Ralf Käthner; Bernd Heinold; Andreas Macke. 2021. "Knowledge Transfer with Citizen Science: Luft-Leipzig Case Study." Sustainability 13, no. 14: 7855.

Preprint content
Published: 04 March 2021
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Clouds influence the shortwave (SW) and longwave (LW) radiative fluxes, thereby affecting the radiative budget by enhancing or diminishing the heat budget at the surface (SFC), at the top of the atmosphere (TOA), and through the atmosphere. In the Arctic, their complexity enhances due to their intrinsic interactions with several physical processes and feedback mechanisms.

With the aim to further investigate the Arctic system, the project (AC)³ (Arctic Amplification: Climate Relevant Atmospheric and SurfaCe Processes and Feedback Mechanisms) established two major field campaigns in summer of 2017. Both performed in situ and remote sensing observations over the ocean with PS106 and in the air with ACLOUD (Macke and Flores, 2018, Wendisch et al., 2019). The observations collected during PS106 are considered to investigate the effects and influence of clouds in the radiation budget for the summer central Arctic.

The PS106 expedition took place aboard the German research vessel Polarstern which was equipped with active and passive remote sensing instrumentation (Griesche et al., 2020). The synergistic operation of this instrumentation was used to derive macro and microphysical properties of clouds by applying the Cloudnet algorithm. These retrievals together with vertical profiles of temperature and relative humidity are used as input to the Rapid Radiative Transfer Model for GCM applications (RRTMG). The results of the broadband SW and LW radiative simulations along with hourly satellite products from Clouds and the Earth’s Radiant Energy System (CERES) Synoptic 1-degree Ed.4. are compared to ship-borne observations indicating a better agreement for single-level liquid clouds than for more challenging sky conditions. The results of the comparison bring sufficient information to discuss a radiative closure assessment for selected case studies and for the entire PS106 expedition. Based on these results the cloud radiative effect (CRE) is calculated indicating a net effect of -8.1 W/m².

The study is extended by applying this methodology to the recent Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC). Preliminary results will be presented for the first leg which will allow a direct comparison of the contrasting properties of cloud radiative effects during summer and winter season.

References

Griesche, H. J., and coauthors. (2020): Application of the shipborne remote sensing supersite OCEANET
for profiling of Arctic aerosols and clouds during Polarstern cruise PS106, Atmos. Meas. Tech., 13,
5335–5358, https://doi.org/10.5194/amt-13-5335-2020

Macke, A. and Flores, H. (2018): The Expeditions PS106/1 and 2 of the Research Vessel POLARSTERN
to the Arctic Ocean in 2017 , Berichte zur Polar- und Meeresforschung = Reports on polar and marine
research, Bremerhaven, Alfred Wegener Institute for Polar and Marine Research, 719 , 171 p.
http://hdl.handle.net/10013/epic.4ff2b0cd-1b2f-4444-a97f-0cd9f1d917ab

Wendisch, M., and coauthors. (2019): The Arctic Cloud Puzzle: Using ACLOUD/PASCAL Multiplatform
Observations to Unravel the Role of Clouds and Aerosol Particles in Arctic Amplification. Bull. Amer.
Meteor. Soc., 100, 841–871, https://doi.org/10.1175/BAMS-D-18-0072.1

ACS Style

Carola Barrientos Velasco; Hartwig Deneke; Hannes Griesche; Anja Hünerbein; Patric Seifert; Andreas Macke. Analysis of cloud radiative effects and radiative budget in the Central Arctic based on satellite and ship-borne observations. 2021, 1 .

AMA Style

Carola Barrientos Velasco, Hartwig Deneke, Hannes Griesche, Anja Hünerbein, Patric Seifert, Andreas Macke. Analysis of cloud radiative effects and radiative budget in the Central Arctic based on satellite and ship-borne observations. . 2021; ():1.

Chicago/Turabian Style

Carola Barrientos Velasco; Hartwig Deneke; Hannes Griesche; Anja Hünerbein; Patric Seifert; Andreas Macke. 2021. "Analysis of cloud radiative effects and radiative budget in the Central Arctic based on satellite and ship-borne observations." , no. : 1.

Preprint content
Published: 29 December 2020
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An advanced multiwavelength polarization Raman lidar was operated aboard the icebreaker Polarstern during the MOSAiC (Multidisciplinary drifting Observatory for the Study of Arctic Climate) expedition, lasting from September 2019 to October 2020, to contiuously monitor aerosol and cloud layers in the Central Arctic up to 30 km height at latitudes mostly between 85° N and 88.5° N. The lidar was integrated in a complex remote sensing infrastructure aboard Polarstern. Modern aerosol lidar methods and new lidar techniques and concepts to explore aerosol-cloud interaction were applied for the first time in the Central Arctic. Aim of the introductory article is to provide an overview of the observational spectrum of the lidar products for representative measurement cases. Highlight of the lidar measurements was the detection of a 10 km deep wildfire smoke layer over the North Pole area from, on average, 7 km to 17 km height with an aerosol optical thickness (AOT) at 532 nm around 0.1 (in October–November 2019) and 0.05 from December to mid of March 2020. The wildfire smoke was trapped within the extraordinarily strong polar vortex and remained detectable until the beginning of May 2020. Arctic haze was also monitored and characterized in terms of backscatter, extinction, and extinction-to-backscatter ratio at 355 and 532 nm. High lidar ratios from 60–100 sr in lofted mixed haze and smoke plumes are indicative for the presence of strongly light-absorbing fine-mode particles. The AOT at 532 nm was of the order of 0.025 for the tropospheric haze layers. In addition, so-called cloud closure experiments were applied to Arctic mixed-phase cloud and cirrus observations. The good match between cloud condensation nucleus concentration (CCNC) and cloud droplet number concentration (CDNC) and, on the other hand, between ice-nucleating particle concentration (INPC) and ice crystal number concentration (ICNC) indicated a clear influence of aerosol particles on the evolution of the cloud systems. CDNC was mostly between 20 and 100 cm−3 in the liquid-water dominated cloud top layer. ICNC was of the order of 0.1–1 L−1. The study of the impact of wildfire smoke particles on cirrus formation revealed that heterogeneous ice formation with smoke particles (organic aerosol particles) as INPs may have prevailed. ICNC values of 10–40 L−1 were clearly below ICNC levels that would indicate homogeneous freezing.

ACS Style

Ronny Engelmann; Albert Ansmann; Kevin Ohneiser; Hannes Griesche; Martin Radenz; Julian Hofer; Dietrich Althausen; Sandro Dahlke; Marion Maturilli; Igor Veselovskii; Cristofer Jimenez; Robert Wiesen; Holger Baars; Johannes Bühl; Henriette Gebauer; Moritz Haarig; Patric Seifert; Ulla Wandinger; Andreas Macke. UTLS wildfire smoke over the North Pole region, Arctic haze, and aerosol-cloud interaction during MOSAiC 2019/20: An introductory. 2020, 2020, 1 -41.

AMA Style

Ronny Engelmann, Albert Ansmann, Kevin Ohneiser, Hannes Griesche, Martin Radenz, Julian Hofer, Dietrich Althausen, Sandro Dahlke, Marion Maturilli, Igor Veselovskii, Cristofer Jimenez, Robert Wiesen, Holger Baars, Johannes Bühl, Henriette Gebauer, Moritz Haarig, Patric Seifert, Ulla Wandinger, Andreas Macke. UTLS wildfire smoke over the North Pole region, Arctic haze, and aerosol-cloud interaction during MOSAiC 2019/20: An introductory. . 2020; 2020 ():1-41.

Chicago/Turabian Style

Ronny Engelmann; Albert Ansmann; Kevin Ohneiser; Hannes Griesche; Martin Radenz; Julian Hofer; Dietrich Althausen; Sandro Dahlke; Marion Maturilli; Igor Veselovskii; Cristofer Jimenez; Robert Wiesen; Holger Baars; Johannes Bühl; Henriette Gebauer; Moritz Haarig; Patric Seifert; Ulla Wandinger; Andreas Macke. 2020. "UTLS wildfire smoke over the North Pole region, Arctic haze, and aerosol-cloud interaction during MOSAiC 2019/20: An introductory." 2020, no. : 1-41.

Journal article
Published: 01 December 2020 in Sustainability
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Air pollution, which kills an estimated 7 million people every year, is one of the greatest environmental health risks of our times. Finding solutions to this threat poses challenges to practitioners and policymakers alike. Increasing awareness on the benefits of transdisciplinary research in solution-oriented sustainable development projects has led to the establishment of the research project “A Transdisciplinary Approach to Mitigate Emissions of Black Carbon” (TAME-BC). This paper introduces the TAME-BC research setup that took place with Metro Manila, Philippines, case study. The approach integrates BC measurements with technological, socio-political, and health aspects to improve the scientific state of the art, policymaking, transport sector planning, and clinical studies related to air pollution health effects. The first pillar in the setup presents an (1) air quality assessment through aerosol measurements and instrumentation, complemented by a (2) description and assessment of the current policies, technologies, and practices of the transport sector that is responsible for pollution levels in the Philippines, as well as a (3) BC exposure and associated health impacts assessment. The fourth pillar is intercrossing, fostering (4) knowledge co-creation through stakeholder involvement across scales. We argue that this transdisciplinary approach is useful for research endeavors aiming for emission mitigation in rapidly urbanizing regions beyond Metro Manila.

ACS Style

Liina Tõnisson; Yvonne Kunz; Simonas Kecorius; Leizel Madueño; Everlyn Tamayo; Dang Casanova; Qi Zhao; Tamara Schikowski; Anna-Katharina Hornidge; Alfred Wiedensohler; Andreas Macke. From Transfer to Knowledge Co-Production: A Transdisciplinary Research Approach to Reduce Black Carbon Emissions in Metro Manila, Philippines. Sustainability 2020, 12, 10043 .

AMA Style

Liina Tõnisson, Yvonne Kunz, Simonas Kecorius, Leizel Madueño, Everlyn Tamayo, Dang Casanova, Qi Zhao, Tamara Schikowski, Anna-Katharina Hornidge, Alfred Wiedensohler, Andreas Macke. From Transfer to Knowledge Co-Production: A Transdisciplinary Research Approach to Reduce Black Carbon Emissions in Metro Manila, Philippines. Sustainability. 2020; 12 (23):10043.

Chicago/Turabian Style

Liina Tõnisson; Yvonne Kunz; Simonas Kecorius; Leizel Madueño; Everlyn Tamayo; Dang Casanova; Qi Zhao; Tamara Schikowski; Anna-Katharina Hornidge; Alfred Wiedensohler; Andreas Macke. 2020. "From Transfer to Knowledge Co-Production: A Transdisciplinary Research Approach to Reduce Black Carbon Emissions in Metro Manila, Philippines." Sustainability 12, no. 23: 10043.

Preprint content
Published: 06 November 2020
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The modification of an existing cloud property retrieval scheme for the Spinning Enhanced Visible and Infrared Imager (SEVIRI) instrument onboard the geostationary METEOSAT satellites is described to utilize its high-resolution visible (HRV) channel for increasing the spatial resolution of its physical outputs. This results in products with a nadir spatial resolution of 1 × 1 km2, compared to the standard 3 × 3 km2 resolution offered by the narrowband channels. This improvement thus greatly reduces the resolution gap between current geostationary and polar-orbiting meteorological satellite imagers. In the first processing step, cloudiness is determined from the HRV observations by a threshold-based cloud masking algorithm. Subsequently, a linear model that links the 0.6 μm, 0.8 μm, and HRV reflectances provides a physical constraint to incorporate the spatial high-frequency component of the HRV observations into the retrieval of cloud optical depth. The implementation of the method is described, including the ancillary datasets used. It is demonstrated that the omission of high-frequency variations in the cloud-absorbing 1.6 μm channel results in comparatively large uncertainties in the retrieved cloud effective radius, likely due to the mismatch in channel resolutions. A newly developed downscaling scheme for the 1.6 μm reflectance is therefore applied to mitigate the effects of this scale mismatch. Benefits of the increased spatial resolution of the resulting SEVIRI products are demonstrated for three example applications: (i) for a convective cloud field, it is shown that significantly better agreement between the distributions of cloud optical depth retrieved from SEVIRI and from collocated MODIS observations is achieved; (ii) the temporal evolution of cloud properties for a growing convective storm at standard and HRV spatial resolutions are compared, illustrating an improved contrast in growth signatures resulting from the use of the HRV channel; (iii) an example of surface solar irradiance, determined from the retrieved cloud properties, is shown, where the HRV channel helps to better capture the large spatio-temporal variability induced by convective clouds. These results suggest that incorporating the HRV channel in the retrieval has potential for improving METEOSAT-based cloud products for several application domains.

ACS Style

Hartwig Deneke; Carola Barrientos-Velasco; Sebastian Bley; Anja Hünerbein; Stephan Lenk; Andreas Macke; Jan Fokke Meirink; Marion Schroedter-Homscheidt; Fabian Senf; Ping Wang; Frank Werner; Jonas Witthuhn. Increasing the spatial resolution of cloud property retrievals from Meteosat SEVIRI by use of its high-resolution visible channel: implementation and examples. 2020, 2020, 1 -36.

AMA Style

Hartwig Deneke, Carola Barrientos-Velasco, Sebastian Bley, Anja Hünerbein, Stephan Lenk, Andreas Macke, Jan Fokke Meirink, Marion Schroedter-Homscheidt, Fabian Senf, Ping Wang, Frank Werner, Jonas Witthuhn. Increasing the spatial resolution of cloud property retrievals from Meteosat SEVIRI by use of its high-resolution visible channel: implementation and examples. . 2020; 2020 ():1-36.

Chicago/Turabian Style

Hartwig Deneke; Carola Barrientos-Velasco; Sebastian Bley; Anja Hünerbein; Stephan Lenk; Andreas Macke; Jan Fokke Meirink; Marion Schroedter-Homscheidt; Fabian Senf; Ping Wang; Frank Werner; Jonas Witthuhn. 2020. "Increasing the spatial resolution of cloud property retrievals from Meteosat SEVIRI by use of its high-resolution visible channel: implementation and examples." 2020, no. : 1-36.

Journal article
Published: 09 October 2020 in Atmospheric Measurement Techniques
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From 25 May to 21 July 2017, the research vessel Polarstern performed the cruise PS106 to the high Arctic in the region north and northeast of Svalbard. The mobile remote-sensing platform OCEANET was deployed aboard Polarstern. Within a single container, OCEANET houses state-of-the-art remote-sensing equipment, including a multiwavelength Raman polarization lidar PollyXT and a 14-channel microwave radiometer HATPRO (Humidity And Temperature PROfiler). For the cruise PS106, the measurements were supplemented by a motion-stabilized 35 GHz cloud radar Mira-35. This paper describes the treatment of technical challenges which were immanent during the deployment of OCEANET in the high Arctic. This includes the description of the motion stabilization of the cloud radar Mira-35 to ensure vertical-pointing observations aboard the moving Polarstern as well as the applied correction of the vessels heave rate to provide valid Doppler velocities. The correction ensured a leveling accuracy of ±0.5∘ during transits through the ice and an ice floe camp. The applied heave correction reduced the signal induced by the vertical movement of the cloud radar in the PSD of the Doppler velocity by a factor of 15. Low-level clouds, in addition, frequently prevented a continuous analysis of cloud conditions from synergies of lidar and radar within Cloudnet, because the technically determined lowest detection height of Mira-35 was 165 m above sea level. To overcome this obstacle, an approach for identification of the cloud presence solely based on data from the near-field receiver of PollyXT at heights from 50 m and 165 m above sea level is presented. We found low-level stratus clouds, which were below the lowest detection range of most automatic ground-based remote-sensing instruments during 25 % of the observation time. We present case studies of aerosol and cloud studies to introduce the capabilities of the data set. In addition, new approaches for ice crystal effective radius and eddy dissipation rates from cloud radar measurements and the retrieval of aerosol optical and microphysical properties from the observations of PollyXT are introduced.

ACS Style

Hannes J. Griesche; Patric Seifert; Albert Ansmann; Holger Baars; Carola Barrientos Velasco; Johannes Bühl; Ronny Engelmann; Martin Radenz; Yin Zhenping; Andreas Macke. Application of the shipborne remote sensing supersite OCEANET for profiling of Arctic aerosols and clouds during Polarstern cruise PS106. Atmospheric Measurement Techniques 2020, 13, 5335 -5358.

AMA Style

Hannes J. Griesche, Patric Seifert, Albert Ansmann, Holger Baars, Carola Barrientos Velasco, Johannes Bühl, Ronny Engelmann, Martin Radenz, Yin Zhenping, Andreas Macke. Application of the shipborne remote sensing supersite OCEANET for profiling of Arctic aerosols and clouds during Polarstern cruise PS106. Atmospheric Measurement Techniques. 2020; 13 (10):5335-5358.

Chicago/Turabian Style

Hannes J. Griesche; Patric Seifert; Albert Ansmann; Holger Baars; Carola Barrientos Velasco; Johannes Bühl; Ronny Engelmann; Martin Radenz; Yin Zhenping; Andreas Macke. 2020. "Application of the shipborne remote sensing supersite OCEANET for profiling of Arctic aerosols and clouds during Polarstern cruise PS106." Atmospheric Measurement Techniques 13, no. 10: 5335-5358.

Journal article
Published: 08 April 2020 in Atmospheric Measurement Techniques
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The role of clouds in recent Arctic warming is not fully understood, including their effects on the solar radiation and the surface energy budget. To investigate relevant small-scale processes in detail, the intensive Physical feedbacks of Arctic planetary boundary layer, Sea ice, Cloud and AerosoL (PASCAL) drifting ice floe station field campaign was conducted during early summer in the central arctic. During this campaign, the small-scale spatiotemporal variability of global irradiance was observed for the first time on an ice floe with a dense network of autonomous pyranometers. A total of 15 stations were deployed covering an area of 0.83 km×1.59 km from 4–16 June 2017. This unique, open-access dataset is described here, and an analysis of the spatiotemporal variability deduced from this dataset is presented for different synoptic conditions. Based on additional observations, five typical sky conditions were identified and used to determine the values of the mean and variance of atmospheric global transmittance for these conditions. Overcast conditions were observed 39.6 % of the time predominantly during the first week, with an overall mean transmittance of 0.47. The second most frequent conditions corresponded to multilayer clouds (32.4 %), which prevailed in particular during the second week, with a mean transmittance of 0.43. Broken clouds had a mean transmittance of 0.61 and a frequency of occurrence of 22.1 %. Finally, the least frequent sky conditions were thin clouds and cloudless conditions, which both had a mean transmittance of 0.76 and occurrence frequencies of 3.5 % and 2.4 %, respectively. For overcast conditions, lower global irradiance was observed for stations closer to the ice edge, likely attributable to the low surface albedo of dark open water and a resulting reduction of multiple reflections between the surface and cloud base. Using a wavelet-based multi-resolution analysis, power spectra of the time series of atmospheric transmittance were compared for single-station and spatially averaged observations and for different sky conditions. It is shown that both the absolute magnitude and the scale dependence of variability contains characteristic features for the different sky conditions.

ACS Style

Carola Barrientos Velasco; Hartwig Deneke; Hannes Griesche; Patric Seifert; Ronny Engelmann; Andreas Macke. Spatiotemporal variability of solar radiation introduced by clouds over Arctic sea ice. Atmospheric Measurement Techniques 2020, 13, 1757 -1775.

AMA Style

Carola Barrientos Velasco, Hartwig Deneke, Hannes Griesche, Patric Seifert, Ronny Engelmann, Andreas Macke. Spatiotemporal variability of solar radiation introduced by clouds over Arctic sea ice. Atmospheric Measurement Techniques. 2020; 13 (4):1757-1775.

Chicago/Turabian Style

Carola Barrientos Velasco; Hartwig Deneke; Hannes Griesche; Patric Seifert; Ronny Engelmann; Andreas Macke. 2020. "Spatiotemporal variability of solar radiation introduced by clouds over Arctic sea ice." Atmospheric Measurement Techniques 13, no. 4: 1757-1775.

Preprint content
Published: 23 March 2020
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ACS Style

Carola Barrientos Velasco; Hartwig Deneke; Andre Ehrlich; Matthias Gottschalk; Hannes Griesche; Anja Hünerbein; Patric Seifert; Johannes Stapf; Andreas Macke. Investigation of cloud radiative effects and closure in the Central Arctic based on ship-borne remote sensing observations. 2020, 1 .

AMA Style

Carola Barrientos Velasco, Hartwig Deneke, Andre Ehrlich, Matthias Gottschalk, Hannes Griesche, Anja Hünerbein, Patric Seifert, Johannes Stapf, Andreas Macke. Investigation of cloud radiative effects and closure in the Central Arctic based on ship-borne remote sensing observations. . 2020; ():1.

Chicago/Turabian Style

Carola Barrientos Velasco; Hartwig Deneke; Andre Ehrlich; Matthias Gottschalk; Hannes Griesche; Anja Hünerbein; Patric Seifert; Johannes Stapf; Andreas Macke. 2020. "Investigation of cloud radiative effects and closure in the Central Arctic based on ship-borne remote sensing observations." , no. : 1.

Journal article
Published: 08 January 2020 in Atmospheric Chemistry and Physics
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The realistic representation of low-level clouds, including their radiative effects, in atmospheric models remains challenging. A sensitivity study is presented to establish a conceptual approach for the evaluation of low-level clouds and their radiative impact in a highly resolved atmospheric model. Considering simulations for six case days, the analysis supports the notion that the properties of clouds more closely match the assumptions of the sub-adiabatic rather than the vertically homogeneous cloud model, suggesting its use as the basis for evaluation. For the considered cases, 95.7 % of the variance in cloud optical thickness is explained by the variance in the liquid water path, while the droplet number concentration and the sub-adiabatic fraction contribute only 3.5 % and 0.2 % to the total variance, respectively. A mean sub-adiabatic fraction of 0.45 is found, which exhibits strong inter-day variability. Applying a principal component analysis and subsequent varimax rotation to the considered set of nine properties, four dominating modes of variability are identified, which explain 97.7 % of the total variance. The first and second components correspond to the cloud base and top height, and to liquid water path, optical thickness, and cloud geometrical extent, respectively, while the cloud droplet number concentration and the sub-adiabatic fraction are the strongest contributors to the third and fourth components. Using idealized offline radiative transfer calculations, it is confirmed that the shortwave and longwave cloud radiative effects exhibit little sensitivity to the vertical structure of clouds. This reconfirms, based on an unprecedented large set of highly resolved vertical cloud profiles, that the cloud optical thickness and the cloud top and bottom heights are the main factors dominating the shortwave and longwave radiative effect of clouds and should be evaluated together with radiative fluxes using observations to attribute model deficiencies in the radiative fluxes to deficiencies in the representation of clouds. Considering the different representations of cloud microphysical processes in atmospheric models, the analysis has been further extended and the deviations between the radiative impact of the single- and double-moment schemes are assessed. Contrasting the shortwave cloud radiative effect obtained from the double-moment scheme to that of a single-moment scheme, differences of about ∼40 W m−2 and significant scatter are observed. The differences are attributable to a higher cloud albedo resulting from the high values of droplet number concentration in particular in the boundary layer predicted by the double-moment scheme, which reach median values of around ∼600 cm−3.

ACS Style

Vasileios Barlakas; Hartwig Deneke; Andreas Macke. The sub-adiabatic model as a concept for evaluating the representation and radiative effects of low-level clouds in a high-resolution atmospheric model. Atmospheric Chemistry and Physics 2020, 20, 303 -322.

AMA Style

Vasileios Barlakas, Hartwig Deneke, Andreas Macke. The sub-adiabatic model as a concept for evaluating the representation and radiative effects of low-level clouds in a high-resolution atmospheric model. Atmospheric Chemistry and Physics. 2020; 20 (1):303-322.

Chicago/Turabian Style

Vasileios Barlakas; Hartwig Deneke; Andreas Macke. 2020. "The sub-adiabatic model as a concept for evaluating the representation and radiative effects of low-level clouds in a high-resolution atmospheric model." Atmospheric Chemistry and Physics 20, no. 1: 303-322.

Journal article
Published: 10 July 2019 in Journal of Advances in Modeling Earth Systems
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In this study Lagrangian large‐eddy simulation (LES) of cloudy mixed‐layers in evolving warm air masses in the Arctic is constrained by in‐situ observations from the recent PASCAL field campaign. A key novelty is that time‐dependence is maintained in the large‐scale forcings. An iterative procedure featuring LES on microgrids is explored to calibrate the case setup, inspired by and making use of the typically long memory of Arctic air masses for upstream conditions. The simulated mixed‐phase clouds are part of a turbulent mixed layer that is weakly coupled to the surface, and is occasionally capped by a shallow humidity layer. All eight simulated mixed layers exhibit a strong time evolution across a range of timescales, including diurnal but also synoptic fingerprints. A few cases experience rapid cloud collapse, coinciding with a rapid decrease in mixed‐layer depth. To gain insight composite budget analyses are performed. In the mixed‐layer interior the heat and moisture budgets are dominated by turbulent transport, radiative cooling and precipitation. However, near the thermal inversion the large‐scale vertical advection also contributes significantly, showing a distinct difference between subsidence and upsidence conditions. A bulk mass budget analysis reveals that entrainment deepening behaves almost time‐constant, as long as clouds are present. In contrast, large‐scale subsidence fluctuates much more strongly, and can both counteract and boost boundary‐layer deepening resulting from entrainment. Strong and sudden subsidence events following prolonged deepening periods are found to cause the cloud collapses, associated with a substantial reduction in the surface downward long wave radiative flux.

ACS Style

R. A. J. Neggers; J. Chylik; U. Egerer; H. Griesche; V. Schemann; P. Seifert; H. Siebert; A. Macke. Local and Remote Controls on Arctic Mixed‐Layer Evolution. Journal of Advances in Modeling Earth Systems 2019, 11, 2214 -2237.

AMA Style

R. A. J. Neggers, J. Chylik, U. Egerer, H. Griesche, V. Schemann, P. Seifert, H. Siebert, A. Macke. Local and Remote Controls on Arctic Mixed‐Layer Evolution. Journal of Advances in Modeling Earth Systems. 2019; 11 (7):2214-2237.

Chicago/Turabian Style

R. A. J. Neggers; J. Chylik; U. Egerer; H. Griesche; V. Schemann; P. Seifert; H. Siebert; A. Macke. 2019. "Local and Remote Controls on Arctic Mixed‐Layer Evolution." Journal of Advances in Modeling Earth Systems 11, no. 7: 2214-2237.

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Published: 01 July 2019
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The realistic representation of low-level clouds, including their radiative effects, in atmospheric models remains challenging. A sensitivity study is presented to establish a conceptual approach for the evaluation of low-level clouds and their radiative impact in a highly resolved atmospheric model. Considering simulations for six case days, the analysis supports that the properties of clouds more closely match the assumptions of the sub-adiabatic rather than the vertically homogeneous cloud model, suggesting its use as basis for evaluation. For the considered cases, 95.7 % of the variance in cloud optical thickness is explained by the variance in the liquid water path, while the droplet number concentration and the sub-adiabatic fraction contribute only 3.5 % and 0.14 % to the total variance, respectively. A mean sub-adiabatic fraction of 0.45 is found, which exhibits strong inter-day variability. Applying a principal component analysis and subsequent varimax rotation to the considered set of nine properties, four dominating modes of variability are identified, which explain 98 % of the total variance. The first and second components correspond to the cloud base and top height, and to liquid water path, optical thickness, and cloud geometrical extent, respectively, while the cloud droplet number concentration and the sub-adiabatic fraction are the strongest contributors to the third and fourth components. Using idealized offline radiative transfer calculations, it is confirmed that the shortwave and longwave cloud radiative effect exhibits little sensitivity to the vertical structure of clouds. Instead, the cloud optical thickness and the cloud top and bottom heights are the dominating factors which determine the shortwave and longwave cloud radiative effects, respectively, with high accuracy. Considering the different representations of cloud microphysical processes in atmospheric models, the analysis has been further extended and the deviations between the radiative impact of the single- and double-moment schemes are assessed. Contrasting the shortwave cloud radiative effect obtained from the double-moment scheme to that of a single moment scheme, a bias of about ~ 40 W m−2 and significant scatter is observed. The bias is attributable to a higher cloud albedo resulting from the high values of droplet number concentration in particular in the boundary layer predicted by the double-moment scheme, which reach median values of around ~ 600 cm−3.

ACS Style

Vasileios Barlakas; Hartwig Deneke; Andreas Macke. The sub-adiabatic model as a concept for evaluating the representation and radiative effects of low-level clouds in a high-resolution atmospheric model. 2019, 2019, 1 -34.

AMA Style

Vasileios Barlakas, Hartwig Deneke, Andreas Macke. The sub-adiabatic model as a concept for evaluating the representation and radiative effects of low-level clouds in a high-resolution atmospheric model. . 2019; 2019 ():1-34.

Chicago/Turabian Style

Vasileios Barlakas; Hartwig Deneke; Andreas Macke. 2019. "The sub-adiabatic model as a concept for evaluating the representation and radiative effects of low-level clouds in a high-resolution atmospheric model." 2019, no. : 1-34.

Preprint content
Published: 17 June 2019
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The role of clouds in recent Arctic warming is not fully understood, including their effects on the shortwave radiation and the surface energy budget. To investigate relevant small-scale processes in detail, an intensive field campaign was conducted during early summer in the central Arctic during the Physical feedbacks of Arctic planetary boundary layer, Sea ice, Cloud and AerosoL (PASCAL) drifting ice floe station. During this campaign, the small-scale spatiotemporal variability of global irradiance was observed for the first time on an ice floe with a dense network of autonomous pyranometers. 15 stations were deployed covering an area of 0.83 km × 1.3 km from June 4–16, 2017. This unique, open-access dataset is described here, and an analysis of the spatiotemporal variability deduced from this dataset is presented for different synoptic conditions. Based on additional observations, 5 typical sky conditions were identified and used to determine the values of the mean and variance of atmospheric global transmittance for these conditions. Overcast conditions were observed 39.6 % of the time predominantly during the first week, with an overall mean transmittance of 0.47. The second-most frequent conditions corresponded to multi-layer clouds (32.4 %) which prevailed in particular during the second week, with a mean transmittance of 0.43. Broken clouds had a mean transmittance of 0.61 and a frequency of occurrence of 22.1 %. Finally, the least frequent sky conditions were thin clouds and cloudless conditions, which both had a mean transmittance of 0.76, and occurrence frequencies of 3.5 % and 2.4 %, respectively. For overcast conditions, lower global irradiance was observed for stations closer to the ice edge, likely attributable to the low surface albedo of dark open water, and a resulting reduction of multiple reflections between the surface and cloud base. Using a wavelet-based multi-resolution analysis, power spectra of the time-series of atmospheric transmittance were compared for single-station and spatially averaged observations, and for different sky conditions. It is shown that both the absolute magnitude and the scale-dependence of variability contains characteristic features for the different sky conditions.

ACS Style

Carola Barrientos Velasco; Hartwig Deneke; Hannes Griesche; Patric Seifert; Ronny Engelmann; Andreas Macke. Spatiotemporal variability of shortwave radiation introduced by clouds over the Arctic sea ice. 2019, 2019, 1 -36.

AMA Style

Carola Barrientos Velasco, Hartwig Deneke, Hannes Griesche, Patric Seifert, Ronny Engelmann, Andreas Macke. Spatiotemporal variability of shortwave radiation introduced by clouds over the Arctic sea ice. . 2019; 2019 ():1-36.

Chicago/Turabian Style

Carola Barrientos Velasco; Hartwig Deneke; Hannes Griesche; Patric Seifert; Ronny Engelmann; Andreas Macke. 2019. "Spatiotemporal variability of shortwave radiation introduced by clouds over the Arctic sea ice." 2019, no. : 1-36.

Journal article
Published: 01 May 2019 in Bulletin of the American Meteorological Society
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Clouds play an important role in Arctic amplification. This term represents the recently observed enhanced warming of the Arctic relative to the global increase of near-surface air temperature. However, there are still important knowledge gaps regarding the interplay between Arctic clouds and aerosol particles, and surface properties, as well as turbulent and radiative fluxes that inhibit accurate model simulations of clouds in the Arctic climate system. In an attempt to resolve this so-called Arctic cloud puzzle, two comprehensive and closely coordinated field studies were conducted: the Arctic Cloud Observations Using Airborne Measurements during Polar Day (ACLOUD) aircraft campaign and the Physical Feedbacks of Arctic Boundary Layer, Sea Ice, Cloud and Aerosol (PASCAL) ice breaker expedition. Both observational studies were performed in the framework of the German Arctic Amplification: Climate Relevant Atmospheric and Surface Processes, and Feedback Mechanisms (AC)3 project. They took place in the vicinity of Svalbard, Norway, in May and June 2017. ACLOUD and PASCAL explored four pieces of the Arctic cloud puzzle: cloud properties, aerosol impact on clouds, atmospheric radiation, and turbulent dynamical processes. The two instrumented Polar 5 and Polar 6 aircraft; the icebreaker Research Vessel (R/V) Polarstern; an ice floe camp including an instrumented tethered balloon; and the permanent ground-based measurement station at Ny-Ålesund, Svalbard, were employed to observe Arctic low- and mid-level mixed-phase clouds and to investigate related atmospheric and surface processes. The Polar 5 aircraft served as a remote sensing observatory examining the clouds from above by downward-looking sensors; the Polar 6 aircraft operated as a flying in situ measurement laboratory sampling inside and below the clouds. Most of the collocated Polar 5/6 flights were conducted either above the R/V Polarstern or over the Ny-Ålesund station, both of which monitored the clouds from below using similar but upward-looking remote sensing techniques as the Polar 5 aircraft. Several of the flights were carried out underneath collocated satellite tracks. The paper motivates the scientific objectives of the ACLOUD/PASCAL observations and describes the measured quantities, retrieved parameters, and the applied complementary instrumentation. Furthermore, it discusses selected measurement results and poses critical research questions to be answered in future papers analyzing the data from the two field campaigns.

ACS Style

Manfred Wendisch; Andreas Macke; André Ehrlich; Christof Lüpkes; Mario Mech; Dmitry Chechin; Klaus Dethloff; Carola Barrientos Velasco; Heiko Bozem; Marlen Brückner; Hans-Christian Clemen; Susanne Crewell; Tobias Donth; Regis Dupuy; Kerstin Ebell; Ulrike Egerer; Ronny Engelmann; Christa Engler; Oliver Eppers; Martin Gehrmann; Xianda Gong; Matthias Gottschalk; Christophe Gourbeyre; Hannes Griesche; Jörg Hartmann; Markus Hartmann; Bernd Heinold; Andreas Herber; Hartmut Herrmann; Georg Heygster; Peter Hoor; Soheila Jafariserajehlou; Evelyn Jäkel; Emma Järvinen; Olivier Jourdan; Udo Kästner; Simonas Kecorius; Erlend Moster Knudsen; Franziska Köllner; Jan Kretzschmar; Luca Lelli; Delphine Leroy; Marion Maturilli; Linlu Mei; Stephan Mertes; Guillaume Mioche; Roland Neuber; Marcel Nicolaus; Tatiana Nomokonova; Justus Notholt; Mathias Palm; Manuela Van Pinxteren; Johannes Quaas; Philipp Richter; Elena Ruiz-Donoso; Michael Schäfer; Katja Schmieder; Martin Schnaiter; Johannes Schneider; Alfons Schwarzenböck; Patric Seifert; Matthew D. Shupe; Holger Siebert; Gunnar Spreen; Johannes Stapf; Frank Stratmann; Teresa Vogl; André Welti; Heike Wex; Alfred Wiedensohler; Marco Zanatta; Sebastian Zeppenfeld. The Arctic Cloud Puzzle: Using ACLOUD/PASCAL Multiplatform Observations to Unravel the Role of Clouds and Aerosol Particles in Arctic Amplification. Bulletin of the American Meteorological Society 2019, 100, 841 -871.

AMA Style

Manfred Wendisch, Andreas Macke, André Ehrlich, Christof Lüpkes, Mario Mech, Dmitry Chechin, Klaus Dethloff, Carola Barrientos Velasco, Heiko Bozem, Marlen Brückner, Hans-Christian Clemen, Susanne Crewell, Tobias Donth, Regis Dupuy, Kerstin Ebell, Ulrike Egerer, Ronny Engelmann, Christa Engler, Oliver Eppers, Martin Gehrmann, Xianda Gong, Matthias Gottschalk, Christophe Gourbeyre, Hannes Griesche, Jörg Hartmann, Markus Hartmann, Bernd Heinold, Andreas Herber, Hartmut Herrmann, Georg Heygster, Peter Hoor, Soheila Jafariserajehlou, Evelyn Jäkel, Emma Järvinen, Olivier Jourdan, Udo Kästner, Simonas Kecorius, Erlend Moster Knudsen, Franziska Köllner, Jan Kretzschmar, Luca Lelli, Delphine Leroy, Marion Maturilli, Linlu Mei, Stephan Mertes, Guillaume Mioche, Roland Neuber, Marcel Nicolaus, Tatiana Nomokonova, Justus Notholt, Mathias Palm, Manuela Van Pinxteren, Johannes Quaas, Philipp Richter, Elena Ruiz-Donoso, Michael Schäfer, Katja Schmieder, Martin Schnaiter, Johannes Schneider, Alfons Schwarzenböck, Patric Seifert, Matthew D. Shupe, Holger Siebert, Gunnar Spreen, Johannes Stapf, Frank Stratmann, Teresa Vogl, André Welti, Heike Wex, Alfred Wiedensohler, Marco Zanatta, Sebastian Zeppenfeld. The Arctic Cloud Puzzle: Using ACLOUD/PASCAL Multiplatform Observations to Unravel the Role of Clouds and Aerosol Particles in Arctic Amplification. Bulletin of the American Meteorological Society. 2019; 100 (5):841-871.

Chicago/Turabian Style

Manfred Wendisch; Andreas Macke; André Ehrlich; Christof Lüpkes; Mario Mech; Dmitry Chechin; Klaus Dethloff; Carola Barrientos Velasco; Heiko Bozem; Marlen Brückner; Hans-Christian Clemen; Susanne Crewell; Tobias Donth; Regis Dupuy; Kerstin Ebell; Ulrike Egerer; Ronny Engelmann; Christa Engler; Oliver Eppers; Martin Gehrmann; Xianda Gong; Matthias Gottschalk; Christophe Gourbeyre; Hannes Griesche; Jörg Hartmann; Markus Hartmann; Bernd Heinold; Andreas Herber; Hartmut Herrmann; Georg Heygster; Peter Hoor; Soheila Jafariserajehlou; Evelyn Jäkel; Emma Järvinen; Olivier Jourdan; Udo Kästner; Simonas Kecorius; Erlend Moster Knudsen; Franziska Köllner; Jan Kretzschmar; Luca Lelli; Delphine Leroy; Marion Maturilli; Linlu Mei; Stephan Mertes; Guillaume Mioche; Roland Neuber; Marcel Nicolaus; Tatiana Nomokonova; Justus Notholt; Mathias Palm; Manuela Van Pinxteren; Johannes Quaas; Philipp Richter; Elena Ruiz-Donoso; Michael Schäfer; Katja Schmieder; Martin Schnaiter; Johannes Schneider; Alfons Schwarzenböck; Patric Seifert; Matthew D. Shupe; Holger Siebert; Gunnar Spreen; Johannes Stapf; Frank Stratmann; Teresa Vogl; André Welti; Heike Wex; Alfred Wiedensohler; Marco Zanatta; Sebastian Zeppenfeld. 2019. "The Arctic Cloud Puzzle: Using ACLOUD/PASCAL Multiplatform Observations to Unravel the Role of Clouds and Aerosol Particles in Arctic Amplification." Bulletin of the American Meteorological Society 100, no. 5: 841-871.

Journal article
Published: 18 December 2018 in Atmospheric Chemistry and Physics
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The two concerted field campaigns, Arctic CLoud Observations Using airborne measurements during polar Day (ACLOUD) and the Physical feedbacks of Arctic planetary boundary level Sea ice, Cloud and AerosoL (PASCAL), took place near Svalbard from 23 May to 26 June 2017. They were focused on studying Arctic mixed-phase clouds and involved observations from two airplanes (ACLOUD), an icebreaker (PASCAL) and a tethered balloon, as well as ground-based stations. Here, we present the synoptic development during the 35-day period of the campaigns, using near-surface and upper-air meteorological observations, as well as operational satellite, analysis, and reanalysis data. Over the campaign period, short-term synoptic variability was substantial, dominating over the seasonal cycle. During the first campaign week, cold and dry Arctic air from the north persisted, with a distinct but seasonally unusual cold air outbreak. Cloudy conditions with mostly low-level clouds prevailed. The subsequent 2 weeks were characterized by warm and moist maritime air from the south and east, which included two events of warm air advection. These synoptical disturbances caused lower cloud cover fractions and higher-reaching cloud systems. In the final 2 weeks, adiabatically warmed air from the west dominated, with cloud properties strongly varying within the range of the two other periods. Results presented here provide synoptic information needed to analyze and interpret data of upcoming studies from ACLOUD/PASCAL, while also offering unprecedented measurements in a sparsely observed region.

ACS Style

Erlend M. Knudsen; Bernd Heinold; Sandro Dahlke; Heiko Bozem; Susanne Crewell; Irina V. Gorodetskaya; Georg Heygster; Daniel Kunkel; Marion Maturilli; Mario Mech; Carolina Viceto; Annette Rinke; Holger Schmithüsen; André Ehrlich; Andreas Macke; Christof Lüpkes; Manfred Wendisch. Meteorological conditions during the ACLOUD/PASCAL field campaign near Svalbard in early summer 2017. Atmospheric Chemistry and Physics 2018, 18, 17995 -18022.

AMA Style

Erlend M. Knudsen, Bernd Heinold, Sandro Dahlke, Heiko Bozem, Susanne Crewell, Irina V. Gorodetskaya, Georg Heygster, Daniel Kunkel, Marion Maturilli, Mario Mech, Carolina Viceto, Annette Rinke, Holger Schmithüsen, André Ehrlich, Andreas Macke, Christof Lüpkes, Manfred Wendisch. Meteorological conditions during the ACLOUD/PASCAL field campaign near Svalbard in early summer 2017. Atmospheric Chemistry and Physics. 2018; 18 (24):17995-18022.

Chicago/Turabian Style

Erlend M. Knudsen; Bernd Heinold; Sandro Dahlke; Heiko Bozem; Susanne Crewell; Irina V. Gorodetskaya; Georg Heygster; Daniel Kunkel; Marion Maturilli; Mario Mech; Carolina Viceto; Annette Rinke; Holger Schmithüsen; André Ehrlich; Andreas Macke; Christof Lüpkes; Manfred Wendisch. 2018. "Meteorological conditions during the ACLOUD/PASCAL field campaign near Svalbard in early summer 2017." Atmospheric Chemistry and Physics 18, no. 24: 17995-18022.

Research article
Published: 09 July 2018 in Atmospheric Chemistry and Physics
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The multi-wavelength Raman lidar PollyXT has been regularly operated aboard the research vessel Polarstern on expeditions across the Atlantic Ocean from north to south and vice versa. The lidar measurements of the RV Polarstern cruises PS95 from Bremerhaven, Germany, to Cape Town, Republic of South Africa (November 2015), and PS98 from Punta Arenas, Chile, to Bremerhaven, Germany (April/May 2016), are presented and analysed in detail. The latest set-up of PollyXT allows improved coverage of the marine boundary layer (MBL) due to an additional near-range receiver. Three case studies provide an overview of the aerosol detected over the Atlantic Ocean. In the first case, marine conditions were observed near South Africa on the autumn cruise PS95. Values of optical properties (depolarisation ratios close to zero, lidar ratios of 23 sr at 355 and 532 nm) within the MBL indicate pure marine aerosol. A layer of dried marine aerosol, indicated by an increase of the particle depolarisation ratio to about 10 % at 355 nm (9 % at 532 nm) and thus confirming the non-sphericity of these particles, could be detected on top of the MBL. On the same cruise, an almost pure Saharan dust plume was observed near the Canary Islands, presented in the second case. The third case deals with several layers of Saharan dust partly mixed with biomass-burning smoke measured on PS98 near the Cabo Verde islands. While the MBL was partly mixed with dust in the pure Saharan dust case, an almost marine MBL was observed in the third case. A statistical analysis showed latitudinal differences in the optical properties within the MBL, caused by the down-mixing of dust in the tropics and anthropogenic influences in the northern latitudes, whereas the optical properties of the MBL in the Southern Hemisphere correlate with typical marine values. The particle depolarisation ratio of dried marine layers ranged between 4 and 9 % at 532 nm. Night measurements from PS95 and PS98 were used to illustrate the potential of aerosol classification using lidar ratio, particle depolarisation ratio at 355 and 532 nm, and Ångström exponent. Lidar ratio and particle depolarisation ratio have been found to be the main indicator for particle type, whereas the Ångström exponent is rather variable.

ACS Style

Stephanie Bohlmann; Holger Baars; Martin Radenz; Ronny Engelmann; Andreas Macke. Ship-borne aerosol profiling with lidar over the Atlantic Ocean: from pure marine conditions to complex dust–smoke mixtures. Atmospheric Chemistry and Physics 2018, 18, 9661 -9679.

AMA Style

Stephanie Bohlmann, Holger Baars, Martin Radenz, Ronny Engelmann, Andreas Macke. Ship-borne aerosol profiling with lidar over the Atlantic Ocean: from pure marine conditions to complex dust–smoke mixtures. Atmospheric Chemistry and Physics. 2018; 18 (13):9661-9679.

Chicago/Turabian Style

Stephanie Bohlmann; Holger Baars; Martin Radenz; Ronny Engelmann; Andreas Macke. 2018. "Ship-borne aerosol profiling with lidar over the Atlantic Ocean: from pure marine conditions to complex dust–smoke mixtures." Atmospheric Chemistry and Physics 18, no. 13: 9661-9679.

Preprint content
Published: 23 May 2018
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The two concerted field campaigns Arctic CLoud Observations Using airborne measurements during polar Day (ACLOUD) and the Physical feedbacks of Arctic planetary boundary level Sea ice, Cloud and AerosoL (PASCAL) took place near Svalbard from 23 May to 26 June 2017. They were focused on studying Arctic mixed-phase clouds and involved observations from two airplanes (ACLOUD), an icebreaker (PASCAL), as well as surface-based stations, a tethered balloon, and satellites. Here, we present the synoptic development during the 35 day period of the campaigns, using classical near-surface and upper-air meteorological observations, as well as operational satellite and model data. Over the campaign period, short-term synoptic variability was substantial, dominating over the long-term background effect of Arctic amplification. During the first campaign week, cold and dry Arctic air from the north persisted, with a distinct but seasonally unusual cold air outbreak. Cloudy conditions with mostly low-level clouds prevailed. The subsequent two weeks were characterized by warm and moist maritime air from the south and east, which included two warm air advections. These synoptical disturbances caused lower cloud cover fractions and higher-reaching cloud systems. In the final two weeks, adiabatically warmed westerly air dominated, with a strongly varying cloud distribution in between the two other periods. Results presented here provide synoptic information needed to analyze and interpret data of upcoming studies from ACLOUD/PASCAL, while also offering unprecedented measurements in a sparsely observed region.

ACS Style

Erlend M. Knudsen; Bernd Heinold; Sandro Dahlke; Heiko Bozem; Susanne Crewell; Georg Heygster; Daniel Kunkel; Marion Maturilli; Mario Mech; Annette Rinke; Holger Schmithüsen; André Ehrlich; Andreas Macke; Christof Lüpkes; Manfred Wendisch. Synoptic development during the ACLOUD/PASCAL field campaign near Svalbard in spring 2017. 2018, 2018, 1 -46.

AMA Style

Erlend M. Knudsen, Bernd Heinold, Sandro Dahlke, Heiko Bozem, Susanne Crewell, Georg Heygster, Daniel Kunkel, Marion Maturilli, Mario Mech, Annette Rinke, Holger Schmithüsen, André Ehrlich, Andreas Macke, Christof Lüpkes, Manfred Wendisch. Synoptic development during the ACLOUD/PASCAL field campaign near Svalbard in spring 2017. . 2018; 2018 ():1-46.

Chicago/Turabian Style

Erlend M. Knudsen; Bernd Heinold; Sandro Dahlke; Heiko Bozem; Susanne Crewell; Georg Heygster; Daniel Kunkel; Marion Maturilli; Mario Mech; Annette Rinke; Holger Schmithüsen; André Ehrlich; Andreas Macke; Christof Lüpkes; Manfred Wendisch. 2018. "Synoptic development during the ACLOUD/PASCAL field campaign near Svalbard in spring 2017." 2018, no. : 1-46.

Journal article
Published: 01 April 2018 in Journal of Quantitative Spectroscopy and Radiative Transfer
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Initially unpolarized solar radiation becomes polarized by scattering in the Earth’s atmosphere. In particular molecular scattering (Rayleigh scattering) polarizes electromagnetic radiation, but also scattering of radiation at aerosols, cloud droplets (Mie scattering) and ice crystals polarizes. Each atmospheric constituent produces a characteristic polarization signal, thus spectro-polarimetric measurements are frequently employed for remote sensing of aerosol and cloud properties. Retrieval algorithms require efficient radiative transfer models. Usually, these apply the plane-parallel approximation (PPA), assuming that the atmosphere consists of horizontally homogeneous layers. This allows to solve the vector radiative transfer equation (VRTE) efficiently. For remote sensing applications, the radiance is considered constant over the instantaneous field-of-view of the instrument and each sensor element is treated independently in plane-parallel approximation, neglecting horizontal radiation transport between adjacent pixels (Independent Pixel Approximation, IPA). In order to estimate the errors due to the IPA approximation, three-dimensional (3D) vector radiative transfer models are required. So far, only a few such models exist. Therefore, the International Polarized Radiative Transfer (IPRT) working group of the International Radiation Commission (IRC) has initiated a model intercomparison project in order to provide benchmark results for polarized radiative transfer. The group has already performed an intercomparison for one-dimensional (1D) multi-layer test cases [phase A, 1]. This paper presents the continuation of the intercomparison project (phase B) for 2D and 3D test cases: a step cloud, a cubic cloud, and a more realistic scenario including a 3D cloud field generated by a Large Eddy Simulation (LES) model and typical background aerosols. The commonly established benchmark results for 3D polarized radiative transfer are available at the IPRT website (http://www.meteo.physik.uni-muenchen.de/~iprt).

ACS Style

Claudia Emde; Vasileios Barlakas; Céline Cornet; Frank Evans; Zhen Wang; Laurent C. Labonotte; Andreas Macke; Bernhard Mayer; Manfred Wendisch. IPRT polarized radiative transfer model intercomparison project – Three-dimensional test cases (phase B). Journal of Quantitative Spectroscopy and Radiative Transfer 2018, 209, 19 -44.

AMA Style

Claudia Emde, Vasileios Barlakas, Céline Cornet, Frank Evans, Zhen Wang, Laurent C. Labonotte, Andreas Macke, Bernhard Mayer, Manfred Wendisch. IPRT polarized radiative transfer model intercomparison project – Three-dimensional test cases (phase B). Journal of Quantitative Spectroscopy and Radiative Transfer. 2018; 209 ():19-44.

Chicago/Turabian Style

Claudia Emde; Vasileios Barlakas; Céline Cornet; Frank Evans; Zhen Wang; Laurent C. Labonotte; Andreas Macke; Bernhard Mayer; Manfred Wendisch. 2018. "IPRT polarized radiative transfer model intercomparison project – Three-dimensional test cases (phase B)." Journal of Quantitative Spectroscopy and Radiative Transfer 209, no. : 19-44.

Preprint content
Published: 28 February 2018
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The multiwavelength Raman lidar PollyXT have been regularly operated aboard the research vessel Polarstern on expeditions across the Atlantic Ocean from North to South and vice versa. The lidar measurements of the Polarstern cruises PS95 from Bremerhaven to Cape Town (November 2015) and PS98 from Punta Arenas to Bremerhaven (April/May 2016) are presented and analysed in detail. The latest setup of PollyXT allows improved coverage of the marine boundary layer (MBL) due to an additional near-range receiver. Three case studies provide an overview of the detected aerosol over the Atlantic Ocean. In the first case, marine conditions were observed near South Africa on the autumn cruise PS95. Values of optical properties (depolarisation ratios close to zero, lidar ratios of 23 sr at 355 nm and 532 nm) within the MBL indicate pure marine aerosol. A layer of dried marine aerosol, indicated by an increase of the particle depolarisation ratio to about 10 % at both wavelengths and thus confirming the non-sphericity of these particles, could be detected on the top the MBL. On the same cruise, an almost pure Saharan dust plume was observed near the Canary Islands, presented in the second case. The third case deals with several layers of Saharan dust partly mixed with biomass-burning smoke measured on PS98 near the Cape Verde Islands. While the MBL was partly mixed with dust in the pure Saharan dust case, an almost marine MBL was observed in the third case. A statistical analysis showed latitudinal differences in the optical properties within the MBL, caused by the down-mixing of dust in the tropics and anthropogenic influences in the northern latitudes whereas the optical properties of the MBL in the southern hemisphere correlate with typical marine values. The particle depolarisation ratio of dried marine layers ranged between 4–9 %. Night measurements from PS95 and PS98 were used to illustrate the potential of aerosol classification using lidar ratio, particle depolarisation ratio and Ångström exponent. Lidar ratio and particle depolarisation ratio have been found to be the main indicator for the particle type, whereas the Ångström exponent is rather variable.

ACS Style

Stephanie Bohlmann; Holger Baars; Martin Radenz; Ronny Engelmann; Andreas Macke. Ship-borne aerosol profiling with lidar over the Atlantic Ocean: From pure marine conditions to complex dust-smoke mixtures. 2018, 2018, 1 -35.

AMA Style

Stephanie Bohlmann, Holger Baars, Martin Radenz, Ronny Engelmann, Andreas Macke. Ship-borne aerosol profiling with lidar over the Atlantic Ocean: From pure marine conditions to complex dust-smoke mixtures. . 2018; 2018 ():1-35.

Chicago/Turabian Style

Stephanie Bohlmann; Holger Baars; Martin Radenz; Ronny Engelmann; Andreas Macke. 2018. "Ship-borne aerosol profiling with lidar over the Atlantic Ocean: From pure marine conditions to complex dust-smoke mixtures." 2018, no. : 1-35.

Journal article
Published: 31 January 2018 in Atmospheric Chemistry and Physics
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This paper examines the representativeness of ground-based in situ measurements for the planetary boundary layer (PBL) and conducts a closure study between airborne in situ and ground-based lidar measurements up to an altitude of 2300 m. The related measurements were carried out in a field campaign within the framework of the High-Definition Clouds and Precipitation for Advancing Climate Prediction (HD(CP)2) Observational Prototype Experiment (HOPE) in September 2013 in a rural background area of central Europe.The helicopter-borne probe ACTOS (Airborne Cloud and Turbulence Observation System) provided measurements of the aerosol particle number size distribution (PNSD), the aerosol particle number concentration (PNC), the number concentration of cloud condensation nuclei (CCN-NC), and meteorological atmospheric parameters (e.g., temperature and relative humidity). These measurements were supported by the ground-based 3+2 wavelength polarization lidar system PollyXT, which provided profiles of the particle backscatter coefficient (σbsc) for three wavelengths (355, 532, and 1064 nm). Particle extinction coefficient (σext) profiles were obtained by using a fixed backscatter-to-extinction ratio (also lidar ratio, LR). A new approach was used to determine profiles of CCN-NC for continental aerosol. The results of this new approach were consistent with the airborne in situ measurements within the uncertainties.In terms of representativeness, the PNSD measurements on the ground showed a good agreement with the measurements provided with ACTOS for lower altitudes. The ground-based measurements of PNC and CCN-NC are representative of the PBL when the PBL is well mixed. Locally isolated new particle formation events on the ground or at the top of the PBL led to vertical variability in the cases presented here and ground-based measurements are not entirely representative of the PBL. Based on Mie theory (Mie, 1908), optical aerosol properties under ambient conditions for different altitudes were determined using the airborne in situ measurements and were compared with the lidar measurements. The investigation of the optical properties shows that on average the airborne-based particle light backscatter coefficient is 50.1 % smaller for 1064 nm, 27.4 % smaller for 532 nm, and 29.5 % smaller for 355 nm than the measurements of the lidar system. These results are quite promising, since in situ measurement-based Mie calculations of the particle light backscattering are scarce and the modeling is quite challenging. In contrast, for the particle light extinction coefficient we found a good agreement. The airborne-based particle light extinction coefficient was just 8.2 % larger for 532 nm and 3 % smaller for 355 nm, for an assumed LR of 55 sr. The particle light extinction coefficient for 1064 nm was derived with a LR of 30 sr. For this wavelength, the airborne-based particle light extinction coefficient is 5.2 % smaller than the lidar measurements. For the first time, the lidar ratio of 30 sr for 1064 nm was determined on the basis of in situ measurements and the LR of 55 sr for 355 and 532 nm wavelength was reproduced for European continental aerosol on the basis of this comparison. Lidar observations and the in situ based aerosol optical properties agree within the uncertainties. However, our observations indicate that a determination of the PNSD for a large size range is important for a reliable modeling of aerosol particle backscattering.

ACS Style

Sebastian Düsing; Birgit Wehner; Patric Seifert; Albert Ansmann; Holger Baars; Florian Ditas; Silvia Henning; Nan Ma; Laurent Poulain; Holger Siebert; Alfred Wiedensohler; Andreas Macke. Helicopter-borne observations of the continental background aerosol in combination with remote sensing and ground-based measurements. Atmospheric Chemistry and Physics 2018, 18, 1263 -1290.

AMA Style

Sebastian Düsing, Birgit Wehner, Patric Seifert, Albert Ansmann, Holger Baars, Florian Ditas, Silvia Henning, Nan Ma, Laurent Poulain, Holger Siebert, Alfred Wiedensohler, Andreas Macke. Helicopter-borne observations of the continental background aerosol in combination with remote sensing and ground-based measurements. Atmospheric Chemistry and Physics. 2018; 18 (2):1263-1290.

Chicago/Turabian Style

Sebastian Düsing; Birgit Wehner; Patric Seifert; Albert Ansmann; Holger Baars; Florian Ditas; Silvia Henning; Nan Ma; Laurent Poulain; Holger Siebert; Alfred Wiedensohler; Andreas Macke. 2018. "Helicopter-borne observations of the continental background aerosol in combination with remote sensing and ground-based measurements." Atmospheric Chemistry and Physics 18, no. 2: 1263-1290.