Wo sollen die Links zur offiziellen Webseite gesetzt werden?
The spatial heterogeneity and temporal evolution of surface properties of the Arctic Ocean influence the radiative energy transfer through the coupled compartments (atmosphere, sea ice, open ocean) of the Arctic climate system. Radiative effects of interactions between these components are not well studied, however, they may play an important role in the Arctic climate system. For example, temporal changes of radiative energy fluxes during the transition period between the onset of sea ice melting and freeze-up are critical, also because these processes are not well represented in the models and, thus, may cause significant uncertainties in projections of the Arctic climate system. Furthermore, the effects of spatially heterogeneous surface conditions, in particular in case of clouds, are not well investigated, although clouds are an important player in Arctic amplification. Therefore, this project will observe the inter-annual and seasonal changes of solar and thermal-infrared radiative flux densities within and through the compartments of the coupled atmosphere-sea ice-ocean system during different sea ice regimes as a function of spatially heterogeneous surface properties (e.g., albedo, temperature, sea ice, and snow thickness). These characteristics and further, more specific surface features (e.g., sea ice types, melt ponds, leads, loe size distributions) as well as the transfer of radiative energy fluxes through the compartments of the system, will be investigated on different spatial and temporal scales by (i) in–situ observations over the full annual cycle below and above the sea ice during MOSAiC, (ii) aircraft measurements on regional and seasonal scales during MOSAiC and the HALO-(AC)³ campaign and (iii) multi-year satellite observations. Based on these sources, we will quantify the influence of the heterogeneity of the surface properties on (i) radiative flux densities in the atmosphere and ocean compartments, (ii) atmospheric cloud radiative forcing (CRF), and (iii) sea ice-ocean interface interactions. Transfer functions quantifying the transition of solar and thermal infrared radiative flux densities between the system compartments will be derived and parameterised. Furthermore, we will continue to improve surface albedo parameterisations established during phase I (e.g., for HIRHAM-NAOSIM) by including additional factors (e.g., cloud cover, surface temperature, melt pond coverage, snow depth). We will analyse airborne data from the previous ACLOUD, PAMARCMiP, and AFLUX campaigns, and collect new measurements during the planned MOSAiC and HALO-(AC)³ observations. In addition we will use satellite data (MERIS, Sentinel-3) in our analysis.