Aerosols are key players in Earth's climate system, with mineral dust being a major component of the atmospheric aerosol load. While former campaigns focused on investigating the properties and effects of layers of rather pure mineral dust, the A-LIFE (Absorbing aerosol layers in a changing climate: aging, lifetime and dynamics) campaign in April 2017 aimed to characterize dust in complex aerosol mixtures. In this study we present ground-based lidar measurements that were performed at Limassol, Cyprus, in April 2017. During our measurement period, the measurement site was affected by complex mixtures of dust from different sources and pollution aerosols from local as well as long-range transported sources. Considering the lidar measurements from two ground-based systems, POLIS (portable lidar system) and PollyXT (portable lidar system with extended capabilities). We found mean values and mean systematic errors (standard deviation, SD​​​​​​​, given in brackets) of the particle linear depolarization ratio and extinction-to-backscatter ratio (lidar ratio) of 0.26 ± 0.03 (SD of 0.02) and 41 ± 5 sr (SD of 3 sr) at 355 nm and of 0.29 ± 0.02 (SD of 0.02) and 38 ± 5 sr (SD of 6 sr) at 532 nm for Arabian dust and of 0.26 ± 0.03 (SD of 0.03) and 55 ± 8 sr (SD of 6 sr) at 355 nm and of 0.28 ± 0.02 (SD of 0.01) and 54 ± 8 sr (SD of 8 sr) at 532 nm for Saharan dust. The values found for pollution aerosols of the particle linear depolarization ratio and the lidar ratio are 0.06 ± 0.02 (SD of 0.04) and 64 ± 13 sr (SD of 5 sr) at 355 nm and of 0.04 ± 0.02 (SD of 0.01) and 64 ± 12 sr (SD of 4 sr) at 532 nm, respectively. We use our measurements for aerosol typing and compare them to aerosol typing from sun photometer data, in situ measurements, and trajectory analysis. The different methods agree well for the derived aerosol type, but looking at the derived dust mass concentration from different methods, the trajectory analysis frequently underestimates high dust concentrations that were found in major mineral dust events.

Aerosol optical properties retrieved from PollyXT lidar located in Mindelo, Cabo Verde. The time frame for the retrieval is between 4:30 - 5:29 UTC. More informantion about the lidar network and data availablitiy at: polly.tropos.de

The presence of aerosol and clouds constitutes one of the highest uncertainties regarding the energy budget of the Earth. Therefore, their continuous observation can help reduce these uncertainties, by providing more information about aerosol-cloud interactions and how these atmospheric components contribute to climate change.To study the properties of aerosols and clouds, new infrastructure will soon be set up in Cyprus by the Eratosthenes Centre of Excellence, which was recently established through the ‘EXCELSIOR’ H2020 Widespread Teaming Project. Eratosthenes Centre of Excellence is a digital innovation hub for Earth Observation, Space Technology and Geospatial Information, aiming to become the reference centre in the East Mediterranean, north Africa and the Middle East (EMMENA region). The infrastructure will be installed in Limassol, on the south coast of the island. Apart from the fact that the site is less than 2 km from the island’s coastline, this location is extremely important in terms of the regional atmospheric composition, as the air masses affecting the site originate from the surrounding areas of EMMENA, as well as from south-eastern Europe.Infrastructure to sample aerosol is already represented by a state-of-the-art PollyXT lidar, with measurements being registered continuously since October 2020. By the end of 2023, a similar LACROS multi-instrument platform will be available for the continuous monitoring of clouds and aerosols. This new ground-based remote sensing platform consists of a 35GHz cloud radar, a ceilometer, a microwave radiometer, a Doppler lidar, and a disdrometer. The infrastructure will be integrated into the Cyprus Atmospheric Remote Sensing Observatory (CARO).An example of the value of the observations about cloud formation and the role of aerosol in the process of cloud formation that will be provided from the site in Limassol, can be reflected in the data collected during the CyCARE campaign, executed between October 2016 and March 2018, during which similar ground-based infrastructure was deployed. The authors acknowledge the ‘EXCELSIOR’: ERATOSTHENES: EΧcellence Research Centre for Earth Surveillance and Space-Based Monitoring of the Environment H2020 Widespread Teaming project (www.excelsior2020.eu). The ‘EXCELSIOR’ project has received funding from the European Union’s Horizon 2020 research and innovation programme under Grant Agreement No 857510, from the Government of the Republic of Cyprus through the Directorate General for the European Programmes, Coordination and Development and the Cyprus University of Technology.

<p>Während MOSAiC (Multidisciplinary drifting Observatory for the Study of Arctic Climate) wurden verschiedene Aerosol- und Wolkentypen mit einem Mehrwellenlängen-Polarisations-Raman-Lidar (Polly-XT) der OCEANET-Atmosphere-Plattform und mit dem KAZR-Wolkenradar der ARM (Atmospheric Radiation Measurement user facility) an Bord des Eisbrechers POLARSTERN beobachtet. Im Winterhalbjahr (2019/20) wurden dafür in der zentralen Arktis regelmäßig Aerosole in Oberflächennähe bis in 4-6 km Höhe (arktischer Dunst) und in der oberen Troposphäre und unteren Stratosphäre (Waldbrandrauch, bis in 18 km Höhe) beobachtet. Neu entwickelte Methoden der Fernerkundung ermöglichen die Bestimmung der Konzentrationen von Wolkenkondensationskernen (CCNC), der Wolkentröpfchenanzahl (CDNC), der eiskeimbildenden Partikel (INPC) und sogar, mit Hilfe von Dopplerradarbeobachtungen, der Eiskristallzahl (ICNC). Gleichzeitig sind Profile der relativen Luftfeuchtigkeit und der Temperatur aus Raman-Lidar, Mikrowellen-Radiometer und Radiosondierungen verfügbar. Mit Hilfe dieses einzigartigen Datensatzes präsentieren wir eine Aerosol-Wolkenschlussstudie, in der wir zeigen, dass CCNC und CDNC sowie INPC und ICNC miteinander verknüpft werden können. Die Ergebnisse können verwendet werden, um zu testen, welche CCN- und INP-Parametrisierungen (aus idealisierten Labormessungen) im arktischen Regime am besten zutreffen. <br>In Anlehnung an diese Methoden werden im zukünftigen Projekt SCiAMO (Smoke Cirrus interaction in the Arctic during MOSAiC) etwa 65 beobachtete Zirren im Hinblick auf Eisnukleationsprozesse in Abhängigkeit vom Auftreten von Rauchpartikeln in der Winter- und Sommersaison analysiert und verglichen.</p>

A new generation PollyXT lidar system start on 27th of October 2020, continuous operation, at Limassol, Cyprus. The lidar system will become a key component within the EXCELSIOR H2020 EU Teaming project coordinated by the Cyprus University of Technology. The mission of the EXCELSIOR project is to upgrade the Remote Sensing & Geo-Environment Lab, established within the Faculty of Engineering & Technology of the Cyprus University of Technology, into a sustainable, viable and autonomous Centre of Excellence, called the ERATOSTHENES Center of Excellence (ECoE). The PollyXT-CYP will be hosted by the ERATOSTHENES CoE for its permanent operation aiming to link the Centre to ACTRIS and PollyNet. Its task will be to document the complex mixture of the different aerosol species and clouds over the Eastern Mediterranean. The system is continuously running and since the first observations in Limassol, PollyXT-CYP demostrates the complex aerosol conditions over Cyprus. For eaxample, between the 27th of October to the 1st of November 2020, the lidar observed smoke plumes from the extreme wildfires on the west coast of the U.S. The smoke travelled over the Atlantic Ocean and triggered the heterogenous ice formation at the height of 10km. Saharan dust was also detected between 2-5km and liquid clouds were formed on the top of the dust layer. In this study we will present selected cases of unique atmospheric structures from the first months of continuous operation over Cyprus as well as optical and geometrical properties of the aerosol layers. The PollyXT-CYP will be a key research infrastructure of the Cyprus Atmospheric Remote Sensing Observatory (CARO). CARO will consist of two high-tech containers housing the PollyXT-CYP lidar and state-of-the art doppler lidar, cloud radar and radiometric equipment which will be used to measure the air quality, the dust transport, and the cloud properties over Cyprus. The CARO is planned to become National Facility of the Republic of Cyprus for Aerosol and Cloud Remote Sensing Observations. Acknowledgements The authors acknowledge the EXCELSIOR project that received funding from the European Union [H2020-WIDESPREAD-04-2017:Teaming Phase2] project under grant agreement no. 857510, and from the Republic of Cyprus. CUT team acknowledge the Research and Innovation Foundation of Cyprus for the financial support through the SIROCCO (EXCELLENCE/1216/0217) and AQ-SERVE (INTERGRATED/0916/0016) projects. The PollyXT-CYP was funded by the German Federal Ministry of Education and Research (BMBF) via the PoLiCyTa project.

The MOSAiC (Multidisciplinary drifting Observatory for the Study of Arctic Climate) expedition, lasting from September 2019 to October 2020, was the largest Arctic research initiative in history. The goal of the expedition was to take the closest look ever at the Arctic as the epicenter of global warming and to gain fundamental insights that are key to better understand global climate change. We continuously operated a multiwavelength aerosol/cloud Raman lidar aboard the icebreaker Polarstern, drifting through the Arctic Ocean trapped in the ice from October to May, and monitored aerosol and cloud layers in the Central Arctic up to 30 km height at latitudes mostly > 85°N. The lidar was integrated in a complex remote sensing infrastructure aboard Polarstern. A polarization Raman lidar is designed to separate the main continental aerosol components (mineral dust, wildfire smoke, anthropogenic haze, volcanic aerosol). Furthermore, the Polarstern lidar enabled us to study the impact of these different basic aerosol types on the evolution of Arctic mixed-phase and ice clouds. The most impressive and unprecedented observation was the detection of a persistent, 10 km deep aerosol layer of aged wildfire smoke over the North Pole region between 8 and 18 km height from October 2019 until the beginning of May 2020. The wildfire smoke layers originated from severe and huge fires in Siberia, Alaska, and western North America in 2019 and may have contained mineral dust injected into the atmosphere over the hot fire places together with the smoke. We will present the main MOSAiC findings including a study of a long-lasting mixed-phase cloud layer evolving in Arctic haze (at heights below 6 km) and the role of mineral dust in the Arctic haze mixture to trigger heterogeneous ice formation. Furthermore, we present a case study developing in the smoke-dominated layer around 10 km height.

The MOSAiC (Multidisciplinary drifting Observatory for the Study of Arctic Climate) expedition, lasting from September 2019 to October 2020, was the largest Arctic research initiative in history. The goal of the expedition was to take the closest look ever at the Arctic as the epicenter of global warming and to gain fundamental insights that are key to better understand global climate change. We continuously operated a multiwavelength aerosol/cloud Raman lidar aboard the icebreaker Polarstern, drifting through the Arctic Ocean trapped in the ice from October to May, and monitored aerosol and cloud layers in the Central Arctic up to 30 km height at latitudes mostly > 85°N. The lidar was integrated in a complex remote sensing infrastructure aboard Polarstern. A polarization Raman lidar is designed to separate the main continental aerosol components (mineral dust, wildfire smoke, anthropogenic haze, volcanic aerosol). Furthermore, the Polarstern lidar enabled us to study the impact of these different basic aerosol types on the evolution of Arctic mixed-phase and ice clouds. The most impressive and unprecedented observation was the detection of a persistent, 10 km deep aerosol layer of aged wildfire smoke over the North Pole region between 8 and 18 km height from October 2019 until the beginning of May 2020. The wildfire smoke layers originated from severe and huge fires in Siberia, Alaska, and western North America in 2019 and may have contained mineral dust injected into the atmosphere over the hot fire places together with the smoke. We will present the main MOSAiC findings including a study of a long-lasting mixed-phase cloud layer evolving in Arctic haze (at heights below 6 km) and the role of mineral dust in the Arctic haze mixture to trigger heterogeneous ice formation. Furthermore, we present a case study developing in the smoke-dominated layer around 10 km height.