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GPS has become an important tool both in navigation and in precise point positioning. One of the nuicance parameters limiting the accuracy of point determination is the water vapor content of the troposphere. On the other hand meteorologists are interested in the wet component of the troposphere as a valuable tool for Numerical Weather Prediction. Therefore GPS offers a low cost monitoring of water vapor with high temporal resolution. We make use of continuous measurements of the GPS/GLONASS reference station network in Austria, which currently consists of about 30 sites with distances ranging from 50 km to 120 km. We calculate the zenith wet delays for a period of 2 months (February and March 2002). Subsequently the results are compared to contributions of different processing centers of the COST-716 project ?Exploitation of Ground Based GPS for Climate and NWP? and with zenith path delay estimates provided by the IGS. As meteorologists need the water vapor within less than two hours, special attention is paid to the availability, reliability and especially to the quality of the satellite orbits used for the network calculations.
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.
In situ measurements of the tropospheric and tropopause and if possible lower stratospheric water vapour content will be carried out with different balloon sondes. Start of up to three balloons with Snow White Sensor-Package prepared by a team from the University of Nagoya and University of Kyoto. Possibly water vapour sondes from NOAA (S. Oltmans) will be started within the scope of an EU-project. This may happen earliest in autumn.
Microwave radiometers are part of the standard instrumentation at primary NDSC stations and are due to their long-term stability and self calibrating technique especially useful for monitoring purposes. Altitude profiles are retrieved from the shape of the pressure broadened thermally induced emission line of the observed species. The instruments for the observation of stratospheric ozone, chlorine monoxide and water vapour at the Koldewey Station in Ny-Ålesund were developed at the University of Bremen and upgrades and improvements are regularly carried out. The instruments have been automated during recent years and ozone and water vapour observation on Spitsbergen are carried out all year round. Chlorine monoxide is only observed in late winter and early spring, when enhanced concentrations in the lower stratosphere are to be expected. Routine operation and maintenance are done by the station engineer. Data analysis is carried out at the University of Bremen.
SAGE III was successfully launched on 10. Dec. 2001 on a Russian M3 rocket. It provides accurate data of aerosols, water vapour, ozone, and other key parameters of the earth's atmosphere. The science team of the SAGE III experiment at NASA has nominated the Koldewey-Station as an anchor site to contribute within the Data Validation Plan as part of the Operational Surface Networks. Data directly relevant to the SAGE III validation are aerosol measurements by photometers and lidar, as well as temperature measurements and ozone profiling by balloon borne sondes, lidar and microwave radiometer. Data will be provided quasi online for immediate validation tasks.
A tropospheric lidar system with a Nd:YAG-Laser was installed at the Koldewey-Station in 1998. It operates at a laser wavelengths of 355, 532, and 1064 nm with detection at 532 nm polarised and depolarised, and at Raman wavelengths like 607nm (nitrogen). It records profiles of aerosol content, aerosol depolarisation and aerosol extinction. During polar night the profils reach from the ground up to the tropopause level, while during polar day background light reduces the altitude range. The main goal of the investigations is to determine the climate impact of arctic aerosol. Analysis of the climate impact will be performed by a high resolution regional model run at the Alfred Wegener Institute (HIRHAM). The lidar system is capable to obtain water vapour profiles in the troposphere. Water vapour profiles are crucial for the understanding of the formation of aerosols. The water vapour profiles are also used for the validation of profiles measured by the CHAMP satellite from 2001 onwards.