A5085555839- Arctic and Antarctic ice dynamics
- Cryospheric studies and observations
- Climate change and permafrost
- Atmospheric aerosols and clouds
- Atmospheric and Environmental Gas Dynamics
- Atmospheric chemistry and aerosols
- Atmospheric Ozone and Climate
- Methane Hydrates and Related Phenomena
- Freezing and Crystallization Processes
- Spacecraft and Cryogenic Technologies
- Icing and De-icing Technologies
- Polar Research and Ecology
- Solar Radiation and Photovoltaics
- Marine and environmental studies
- Solar and Space Plasma Dynamics
- Winter Sports Injuries and Performance
- Aerospace Engineering and Energy Systems
- Marine and fisheries research
- Meteorological Phenomena and Simulations
- Calibration and Measurement Techniques
- Healthcare Systems and Challenges
- Geological Studies and Exploration
- Food Industry and Aquatic Biology
- Space Exploration and Technology
- Optical Polarization and Ellipsometry
University of Bremen
2015-2024
Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung
2020-2024
Space Research Institute
1988
Abstract Melt ponds forming on Arctic sea ice in summer significantly reduce the surface albedo and impact heat mass balance of ice. Therefore, their areal coverage, which can undergo rapid change, is crucial to monitor. We present a revised method extract melt pond fraction (MPF) from Sentinel‐2 satellite imagery, evaluated by MPF products higher‐resolution helicopter‐borne imagery. The analysis evolution during MOSAiC campaign 2020, shows split Central Observatory (CO) into level highly...
Abstract. White ice (ice with a highly scattering granular layer on top of its surface) and snow-covered occupy large part the sea area in Arctic, former summer, latter cold period. The inherent optical properties (IOPs) reflectance these types are considered from point view light radiative transfer theories. IOPs – extinction absorption coefficients phase function derived assumption that both snow cover white random mixtures air characteristic grain size significantly larger than wavelength...
Abstract. The presence of melt ponds on the Arctic sea ice strongly affects energy balance Ocean in summer. It albedo as well transmittance through ice, which has consequences for heat and mass ice. An algorithm to retrieve pond fraction from Medium Resolution Imaging Spectrometer (MERIS) data is validated against aerial, shipborne situ campaign data. results show best correlation landfast multiyear high concentrations. For broadband albedo, R2 equal 0.85, with RMS (root mean square) being...
Abstract. Observations of sea-ice concentration are available from satellites year-round and almost weather-independently using passive microwave radiometers at resolutions down to 5 km. Thermal infrared provide data with a resolution 1 km but only under cloud-free conditions. We use the best two satellite measurements merge thermal concentrations. This yields merged product combining gap-free spatial coverage concentration. The benefit is demonstrated by observations polynya which opened...
Abstract. For the determination of aerosol optical thickness (AOT) Bremen AErosol Retrieval (BAER) has been developed. Method and main features on retrieval are described together with validation results. The separates spectral reflectance from surface Rayleigh path for shortwave range measured spectrum top-of-atmosphere wavelength less than 0.670 μm. advantage MERIS (Medium Resolution Imaging Spectrometer Environmental Satellite – ENVISAT European Space Agency ESA) SeaWiFS (Sea viewing Wide...
Abstract. Melt ponds on Arctic sea ice affect the radiative balance of region as they introduce darkening during summer. The temporal extent and spatial ponding, well its amplitude, reflect state are important for our understanding change. Remote sensing retrievals melt pond fraction (MPF) provide information both present development change throughout years, which is valuable in context climate amplification. In this work, we transfer earlier published Pond Detector (MPD) remote retrieval to...
Abstract. Melt ponds occupy a large part of the Arctic sea ice in summer and strongly affect radiative budget atmosphere–ice–ocean system. In this study, melt pond reflectance is considered framework transfer theory. The modeled as plane-parallel layer pure water upon (the bottom). We consider reflection comprising Fresnel by surface multiple reflections between its bottom, which assumed to be Lambertian. order give description how find bottom albedo, we investigate inherent optical...
Abstract. The spatial and temporal dynamics of melt ponds sea ice albedo contain information on the current state trend climate Arctic region. This publication presents a study pond fraction (MPF) obtained with Melt Pond Detection (MPD) retrieval scheme for Medium Resolution Imaging Spectrometer (MERIS) satellite data. compares MPF to surface air temperature reanalysis data, retrieved from Moderate Spectroradiometer (MODIS), examines trends. Weekly averages 2007 2011 showed different while...
Abstract. The presence of melt ponds on Arctic summer sea ice significantly alters its albedo and thereby the surface energy budget mass balance. Large-scale observations pond coverage are crucial to investigate role for amplification representation in global climate models. We present new Melt Pond Detection 2 (MPD2) algorithm, which retrieves pond, ice, open-ocean fractions as well from Sentinel-3 visible near-infrared reflectances. In contrast most other algorithms, our method uses...
Abstract. A new method to detect cloud-free snow-covered areas has been developed using the measurements by Advanced Along Track Scanning Radiometer (AATSR) on board ENVISAT satellite in order discriminate clear snow fields for retrieval of aerosol optical thickness or properties. The algorithm uses seven AATSR channels from visible (VIS) thermal infrared (TIR) and analyses spectral behaviour each pixel recognize signature snow. includes a set relative thresholds combines all into one...
Abstract. Infrared (IR) retrievals of aerosol optical thickness (AOT) are challenging because the low reflectance layer at longer wavelengths. In this paper we present a closer analysis problem, performed with radiative transfer (RT) simulations for coarse and accumulation mode four main components. It shows strong angular dependence IR solar elevations resulting from significant asymmetry phase function these This results in detectable values certain non-nadir observation angles providing...
Abstract. Pond color, which creates the visual appearance of melt ponds on Arctic sea ice in summer, is quantitatively investigated using a two-stream radiative transfer model for ponded ice. The upwelling irradiance from pond surface determined and then its spectrum transformed into RGB (red, green, blue) color space colorimetric method. dependence various factors such as water properties incident solar radiation investigated. results reveal that increasing underlying thickness Hi enhances...
Abstract. The optical-equivalent snow grain size affects the reflectivity of surfaces and, thus, local surface energy budget in particular polar regions. Therefore, specific area (SSA), from which optical is derived, was observed for a 2-month period central Antarctica (Kohnen research station) during austral summer 2013/14. data were retrieved on basis ground-based spectral albedo measurements collected by COmpact RAdiation measurement System (CORAS) and airborne observations with Spectral...
Abstract. Arctic summer sea ice experiences rapid changes in its sea-ice concentration, surface albedo, and the melt pond fraction. This affects energy balance of region demands an accurate knowledge those characteristics climate models. In this paper, broadband albedo (300–3000 nm) is derived from MEdium Resolution Imaging Spectrometer (MERIS) optical swath data by transforming spectral as output Melt Pond Detector (MPD) algorithm with a newly developed spectral-to-broadband conversion...
The detection, monitoring, and forecasting of sea-ice conditions, including their extremes, is very important for ship navigation offshore activities, monitoring processes trends. We summarize here recent advances in the conditions extremes from satellite data as well development seasonal capabilities. Our results are outcome three-year (2015–2018) SPICES (Space-borne Observations Detecting Forecasting Sea-Ice Cover Extremes) project funded by EU’s Horizon 2020 programme. New products...
The ongoing decline of sea ice threatens many Arctic taxa, including the ivory gull. Understanding how ice-edges and concentrations influence distribution endangered gulls is a prerequisite to implementation adequate conservation strategies. From 2007 2013, we used satellite transmitters monitor movements 104 originating from Canada, Greenland, Svalbard-Norway Russia. Although half positions were within 41 km ice-edge (75% 100 km), approximately 80% on relatively highly concentrated ice....
Abstract. Since clouds play an essential role in the Earth's climate system, it is important to understand cloud characteristics as well their distribution on a global scale using satellite observations. The main scientific objective of SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY) onboard ENVISAT retrieval vertical columns trace gases. On one hand, has be sensitive low variations gas concentrations which means ground pixel size large enough. other such...
Aerosol observations over the Arctic are important because of effects aerosols on climate, such as their direct and indirect Earth's radiation balance snow albedo. Although information aerosol properties is available from ground-based measurements, passive remote sensing using satellite measurements would offer advantage large spatial coverage with good temporal resolution, even though, due to light limitations, this only during summer. However, optical depth (AOD) retrieval region a great...
The size and shape of snow grains directly impacts the reflection by a snowpack. In this article, different approaches to retrieve optical-equivalent grain (ropt) or, alternatively, specific surface area (SSA) using satellite, airborne, ground-based observations are compared used evaluate ICON-ART (ICOsahedral Nonhydrostatic—Aerosols Reactive Trace gases) simulations. retrieval methods based on optical measurements rely ropt-dependent absorption solar radiation in snow. measurement data were...
Abstract. Infrared (IR) retrievals of aerosol optical thickness (AOT) are challenging because the low reflectance layer at longer wavelengths. In this paper we present a closer analysis problem, performed with radiative transfer (RT) simulations for coarse and accumulation mode four main components. It shows strong angular dependence IR solar elevations resulting from significant asymmetry phase function these This results in detectable values certain non-nadir observation angles providing...