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  • 1. Katlein, Christian
    An open-source albedo-wand for the measurement of sea ice albedo2019In: Advances in polar science, ISSN 1674-9928, Vol. 30, no 2, p. 106-117Article in journal (Refereed)
    Abstract [en]

    Surface albedo is defined as the ratio of incident and reflected solar irradiance and describes the ability of a surface to reflect, rather than absorb incident solar shortwave radiation. It is thus a crucial parameter in the climate system, particularly in the polar oceans. Sea ice albedo is a main driver for light transmission into the polar oceans and thus has a high impact on ocean warming, ice melting and marine primary production. During spring and summer, sea ice albedo can exhibit a significant spatial variability caused by meltwater accumulations on the ice. While complex and expensive solutions for albedo measurements are already available, we want to present a simple open-source design that allows for affordable mapping of spatially varying surface albedo on sea ice and beyond. Our solution is based on off-the-shelf components, such as an Arduino microcontroller integrating affordable light sensors, a GPS unit, data recording on memory card and data display into a simple field strengthened unit. We provide example data from two Arctic field deployments showing the capabilities and limitations of this system.

  • 2. Katlein, Christian
    et al.
    Labaste, Matthieu
    Hoppmann, Mario
    Manual Recovery of a Sea Ice Based Ocean Profiler2019In: Frontiers in Marine Science, E-ISSN 2296-7745, Vol. 6Article in journal (Refereed)
    Abstract [en]

    Ice-tethered ocean profiling systems are an essential tool for the year-round observation of physical and biogeochemical properties of the Arctic Ocean. Despite being considered expendable equipment due to the challenging logistics, their recovery is attractive mainly due to two factors: If the sensors can be retrieved, this allows for their post calibration, which helps to assess sensor drift and biofouling. In addition, the recovery of such expensive equipment can ease off financial pressure on autonomous ocean observation programs by enabling the reuse of central elements after refurbishment. Here we present a method how such profiling systems can be recovered from sea ice by 3 people in about 4 h, without the on-site availability of a fully-equipped vessel. The presented technique combines rope techniques from mountain rescue applications with lightweight equipment and procedures similar to those used for the deployment of such instruments. We provide a detailed description of the whole process, provide suggestions for potential improvements as well as suggestions toward improved instrument design favoring recoverability of future deployments. We conclude that good preparation and practice of the relevant rope procedures is critical to mission success and that a well-selected range of necessary equipment makes the process much more efficient.

  • 3. Naakka, T.
    et al.
    Nygård, T.
    Tjernström, Michael
    Stockholms universitet, Meteorologiska institutionen (MISU).
    Vihma, T.
    Pirazzini, R.
    Brooks, I. M.
    The Impact of Radiosounding Observations on Numerical Weather Prediction Analyses in the Arctic2019In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 46, no 14, p. 8527-8535Article in journal (Refereed)
    Abstract [en]

    The radiosounding network in the Arctic, despite being sparse, is a crucial part of the atmospheric observing system for weather prediction and reanalysis. The spatial coverage of the network was evaluated using a numerical weather prediction model, comparing radiosonde observations from Arctic land stations and expeditions in the central Arctic Ocean with operational analyses and background fields (12-hr forecasts) from European Centre for Medium-Range Weather Forecasts for January 2016 to September 2018. The results show that the impact of radiosonde observations on analyses has large geographical variation. In data-sparse areas, such as the central Arctic Ocean, high-quality radiosonde observations substantially improve the analyses, while satellite observations are not able to compensate for the large spatial gap in the radiosounding network. In areas where the network is reasonably dense, the quality of background field is more related to how radiosonde observations are utilized in the assimilation and to the quality of those observations.

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