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Displaying: 1 - 5 of 5
1. Mechanisms of fluvial transport and sediment supply to Arctic river channels with various hydrological regimes (SW Spitsbergen) (ARCTFLUX)

Fluvial transport, its dynamics and structure, constitute a good indicator of the condition of the natural environment in various climatic zones. Analysis of fluvial transport components allows for precise determination of the rate and directions of transformations of geosystems of any importance. In the polar zone, very sensitive to global changes, it seems expedient to identify the mechanisms and structure of fluvial transport, particularly in the conditions of the observed glacier retreat, the main alimentation source of proglacial rivers. Studies carried out in the zone revealed difficulties in determination of fluvial transport structure, particularly the actual bedload of gravel-bed rivers based on direct measurements, resulting from: short measurement series, lack of standardization of research methods and measurement equipment, and strategy of selection of study objects and sampling. The research project presented concerns determination of mechanisms of fluvial transport and sediment supply to Arctic gravel-bed river channels. The mechanisms reflect the processes of adaptation of proglacial rivers of the Arctic zone to changing environmental conditions, and indicate the dominant directions of transformations of paraglacial geosystems of various importance. For studies on Arctic geosystems, the region of the south Bellsund (SW Spitsbergen) was selected due to extensive knowledge on its hydro-meteorological and glacial-geomorphological conditions, and long-term measurement series carried out by the research station of the MCSU, among others within the framework of the international monitoring network: SEDIBUD (IAG) and Small-CATCHMENT program. For detailed studies, rivers with various hydrological regimes were selected, functioning at the forefield of the Scott and Renard Glaciers. The Scott River glacial catchment and glacier-free catchments of the Reindeer Stream and the Wydrzyca Stream (with a snow-permafrost hydrological regime) meet the selection criteria for representative test catchments analyzed for the following programs: SEDIFLUX, SEDIBUD, and POP.

conductivity cryosphere deposition Discharges distribution erosion freshwater freshwater flux geomorphology GIS Glaciers GPS ice thickness lidar Mapping mass balance remote-sensing riverine transport rivers runoff sediment balance surface water Water currents Water flux
2. Stratosphere-mesosphere intercomparison of ozone profil

During the past years, atmospheric research in high latitudes has been focussed on processes causing ozone loss in the polar winter lower stratosphere1). Recent research efforts also dealt with regions up to the lower mesosphere, and studied the effects of charged particle precipitation on NO and ozone2)-5). However, the measurement techniques and hence the database for studying such processes in this altitude range are very limited. The Airborne SUbmillimeter Radiometer ASUR6),7) of the Institute of Environmental Physics of the University of Bremen has recently been equipped with a high-resolution spectrometer that will enable the retrieval of vertical profiles of ozone up to an altitude of about 65 - 70 km. Its measurement capabilities comprise also several other species of interest, especially NO. This makes the measurement technique particularly suitable for upper stratospheric/lower mesospheric studies. The lidar at ALOMAR is capable of measuring highly resolved vertical profiles of ozone up to an altitude of 60 km, thus giving the rare opportunity for intercomparison and validation studies in an altitude range reaching from the lower stratosphere to the lower mesosphere. Therefore we propose to perform simultaneous ozone measurements of the ASUR instrument with the ALOMAR lidar, supported by launches of ozone sondes.

Atmospheric processes Ozone Geophysics radiometer Climate Arctic Atmosphere lidar
3. Ground-based observations of noctilucent clouds With the shortest possible wavelength (308 nm)

Noctilucent clouds (NLC) remain a fascinating phenomenon of the upper atmosphere to study. The questions about the typical particle density and particle size distribution within a NLC are very prominent ones, to which a number of answers have been given, though some of the answers contradict each other. The parameters of particle size distributions can be derived from groundbased lidar measurements of the spectral dependence of the volume backscatter coefficient of an NLC. Such studies have been performed during a number of NLC events by e.g. the ALOMAR Rayleigh/Mie/Raman (RMR) lidar (von Cossart et al., GRL, 26, 1513, 1999). A drawback of these experiments is the wavelength limitation of the RMR lidar, the shortest wavelength of which is 355 nm. At this wavelength, the sensitivity of the lidar to particles with sizes smaller than, say, 25 nm is minimal. Because a considerable part of the entire particle population may have sizes below that threshold, a lingering question remains whether or not this drawback matters for typical NLC distributions. Using the ALOMAR ozone lidar, a measurement of the NLC volume backscatter coefficient at 308 nm becomes possible. Due to the l-4 -dependence of the backscatter coefficients, the latter are almost a factor of 2 larger at this wavelength than at 355 nm. For this reason and in order to gain a fourth wavelength to the spectral distribution, we aim at using the ozone lidar for the outlined project.

Atmospheric processes Climate NLC Arctic Atmosphere lidar
4. Marine aerosols with LIDAR and photometer

Situated in the Arctic Ocean the planetary boundary layer over Ny Ålesund is dominated by marine aerosols. Hight and time variation of boundary layer aerosols are examined with the tropospheric lidar system in Ny Ålesund. To determine the aerosol and its optical properties more exactly information from more wavelenghts are necessary as the sun-photometer at the Koldewey Station can provide. First combined evaluation of photometer and LIDAR data during the ASTAR-campaign in spring 2000 demonstrated feasibility and advantages of this method for the free troposphere. Furthermore this method is to be applied on boundary layer aerosol to research also its optical properties.

Aerosols Atmospheric processes Climate variability Climate NDSC ASTAR Climate change Arctic Water vapour Atmosphere LIDAR Troposphere Boundary layer Photometer
5. Stratospheric observations with LIDAR technique (NDSC)

The stratospheric multi wavelength LIDAR instrument, which is part of the NDSC contribution of the Koldewey-Station, consists of two lasers, a XeCl-Excimer laser for UV-wavelengths and a Nd:YAG-laser for near IR- and visible wavelengths, two telescopes (of 60 cm and 150 cm diameter) and a detection system with eight channels. Ozone profiles are obtained by the DIAL method using the wavelengths at 308 and 353 nm. Aerosol data is recorded at three wavelengths (353 nm, 532 nm, 1064 nm) with depolarization measurements at 532 nm. In addition the vibrational N2-Raman scattered light at 608 nm is recorded. As lidar measurements require clear skies and a low background light level, the observations are concentrated on the winter months from November through March. The most prominent feature is the regular observation of Polar Stratospheric Clouds (PSCs). PSCs are known to be a necessary prerequisite for the strong polar ozone loss, which is observed in the Arctic (and above Spitsbergen). The PSC data set accumulated during the last years allows the characterization of the various types of PSCs and how they form and develop. The 353 and 532 nm channels are also used for temperature retrievals in the altitude range above the aerosol layer up to 50 km.

Aerosols Atmospheric processes Ozone Polar Stratospheric Clouds UV radiation Geophysics Climate variability stratosphere Climate Climate change Aerosol Arctic PSCs Atmosphere LIDAR UV