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  • 1
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    Divergent consensuses on Arctic amplification influence on midlatitude severe winter weather (2020)
    In:  Nature Climate Change
    Details
    Publication Date: 2023-07-27
    Description: The Arctic has warmed more than twice as fast as the global average since the late twentieth century, a phenomenon known as Arctic amplification (AA). Recently, there have been considerable advances in understanding the physical contributions to AA, and progress has been made in understanding the mechanisms that link it to midlatitude weather variability. Observational studies overwhelmingly support that AA is contributing to winter continental cooling. Although some model experiments support the observational evidence, most modelling results show little connection between AA and severe midlatitude weather or suggest the export of excess heating from the Arctic to lower latitudes. Divergent conclusions between model and observational studies, and even intramodel studies, continue to obfuscate a clear understanding of how AA is influencing midlatitude weather.
    Type: info:eu-repo/semantics/article
    Format: application/pdf
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  • 2
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    Research Agenda Polar Regions in Transition. Concept Paper of the Mare:N Scientific Advisory Board, Executive Summary (2021)
    Mare:N “Research Agenda Polar Regions in Transition” Scientific Advisory Board
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    Publication Date: 2023-07-18
    Description: Leading experts from various fields of German polar and marine research presented an executive summary of the MARE:N concept paper “Polar Regions in Transition” to the German Federal Ministry of Education and Research (BMBF). In 15 chapters, the paper presents recommendations on the areas in which polar and marine research should be particularly committed in the coming years. The BMBF will take up the recommendations at short notice, developing future research programmes in the context of pending political processes and national, European and international frameworks.
    Language: English
    Type: info:eu-repo/semantics/report
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  • 3
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    HALO-AC3: An airborne campaign to observe airmass transformations (2023)
    In:  XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)
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    Publication Date: 2023-07-20
    Description: Clear indications of the phenomenon of Arctic Amplification include the above-average increase of the near-surface air temperature and the dramatic retreat of sea ice observed in the last decades. The mechanisms behind these features are widely discussed. Especially the role of clouds and of air mass transports into and out of the Arctic associated with related transformation processes are still poorly understood. Therefore, the HALO-(AC)3 campaign was performed to provide observations of meridional air mass transports and corresponding transformations in a quasi-Langrangian approach. Three research aircraft equipped with state-of-the-art instrumentation performed measurements over the Arctic ocean and sea ice in March/April 2022. The German High Altitude and Long Range Research Aircraft (HALO), equipped with a comprehensive suite of active and passive remote sensing instruments and dropsondes, was operated from Kiruna, Sweden. The flight pattern covered long distances at high altitudes up to the North Pole probing air masses multiple times on their way into and out of the Arctic. The Polar 5 (remote sensing) and Polar 6 (in-situ) aircraft from the Alfred Wegener Institute operated in the lower troposphere out of Longyearbyen in the lower troposphere over Fram Strait West of Svalbard. Several coordinated flights between the three aircraft were conducted with Polar 6 sampling in-situ aerosol, cloud, and precipitation particles within the boundary layer, Polar 5 observing clouds and precipitation from above roughly at 3 km altitude, and HALO providing the large scale view on the scene following air masses. The paper reports on first results of the campaign.
    Language: English
    Type: info:eu-repo/semantics/conferenceObject
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  • 4
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    Airborne remote sensing observations of Arctic low-level clouds and precipitation during cold air outbreaks (2023)
    In:  XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)
    Details
    Publication Date: 2023-07-12
    Description: In cold air outbreaks (CAOs), cold and dry air flows from the central Arctic southward often leading to extreme weather at mid-latitudes. Roll convection in the boundary layer is triggered within the marginal sea ice zone. During the air-mass transformation, this roll convection leads to cloud formation within several 100 km away from the sea ice edge. Mixed-phase processes and extreme surface heat fluxes play an important role in the transformation. Understanding air-mass transformation is very important for weather and climate modelling. However, only few observations of cloud macro- and microphysical characteristics during CAOs along their trajectory exist yet.Our study investigates cloud rolls over the open ocean and sea ice west of Spitsbergen using airborne remote sensing measurements obtained by the Microwave Radar/radiometerfor Arctic Clouds (MiRAC) and Airborne Mobile Aerosol Lidar for Arctic research (AMALi). We focus on two CAO events that took place during the HALO–(AC)3 campaign conducted in March/April 2021. The POLAR 5 aircraft flew several legs along the same track perpendicular to the cloud streets crossing the sea ice edge. This allows an investigation of the air masses with time and distance to sea ice edge. Hence, our analysis resolves the development of the roll convection. Dropsondes serve information of the thermodynamic state of the atmosphere, whereas remote sensing observations allow for a geometrical and microphysical analysis of clouds. In-situ measurements from the POLAR 6 aircraft, which flew collocated with P5 but inside the clouds, resolve aerosol number concentrations and droplet size distributions.
    Language: English
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  • 5
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    Impact of clouds and extreme climatic conditions on forest albedo and surface radiation budget (2023)
    In:  XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)
    Details
    Publication Date: 2023-08-02
    Description: Clouds and seasonal variations are key parameters that play a crucial role in the albedo dynamics of forest canopies that ultimately impact the surface radiation budget and long-term climate trends. Additionally, the occurrence of natural extreme events such as prolonged dry spells or floods may further alter the feedback loop between the forest canopy and the Earth’s energy radiation budget. Limitations such as low spatio-temporal resolution in case of satellite-based analyses and lack of continuous in-situ observations hinder efforts to quantify the local effects of forest-cloud dynamics on climatic trends. To this effect, we have established a long-term autonomous measurement system on a crane within the Leipzig floodplain area, Leipzig, Germany, operational since June 2, 2021. We present a comparative analysis of the spectral forest canopy albedo as a function of cloud fraction for two consecutive years with different climatic conditions: year 2021 with conditions close to the climatological mean and year 2022 with a close to eight weeks long dry spell during summer months. The spectral irradiance is recorded daily between 12 Noon and 1 P.M. local time and the cloud fraction is obtained from the Tropomi sensor onboard the Sentinel-5P satellite. The results indicate a substantial dependence of the spectral canopy albedo on the cloud fraction and an overall increased canopy albedo for the year 2022 compared to the year 2021, which shows the biophysical impact of clouds on forests and the feedback mechanism of forest-cloud dynamics following an extreme event.
    Language: English
    Type: info:eu-repo/semantics/conferenceObject
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  • 6
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    Atmospheric and Surface Processes, and Feedback Mechanisms Determining Arctic Amplification: A Review of First Results and Prospects of the (AC)3 Project (2023)
    American Meteorological Society
    In:  EPIC3Bulletin of the American Meteorological Society, American Meteorological Society, 104(1), pp. e208-e242, ISSN: 0003-0007
    Details
    Publication Date: 2023-04-26
    Description: Mechanisms behind the phenomenon of Arctic amplification are widely discussed. To contribute to this debate, the (AC)3 project was established in 2016 (www.ac3-tr.de/). It comprises modeling and data analysis efforts as well as observational elements. The project has assembled a wealth of ground-based, airborne, shipborne, and satellite data of physical, chemical, and meteorological properties of the Arctic atmosphere, cryosphere, and upper ocean that are available for the Arctic climate research community. Short-term changes and indications of long-term trends in Arctic climate parameters have been detected using existing and new data. For example, a distinct atmospheric moistening, an increase of regional storm activities, an amplified winter warming in the Svalbard and North Pole regions, and a decrease of sea ice thickness in the Fram Strait and of snow depth on sea ice have been identified. A positive trend of tropospheric bromine monoxide (BrO) column densities during polar spring was verified. Local marine/biogenic sources for cloud condensation nuclei and ice nucleating particles were found. Atmospheric–ocean and radiative transfer models were advanced by applying new parameterizations of surface albedo, cloud droplet activation, convective plumes and related processes over leads, and turbulent transfer coefficients for stable surface layers. Four modes of the surface radiative energy budget were explored and reproduced by simulations. To advance the future synthesis of the results, cross-cutting activities are being developed aiming to answer key questions in four focus areas: lapse rate feedback, surface processes, Arctic mixed-phase clouds, and airmass transport and transformation.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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