Koldewey Station, Ny-Ålesund/Spitsbergen: projects/activities

In preparation to the launch of the SAGE III experiment in March 2001, NASA and the European Union performed the SOLVE / THESEO-2000 campaign, which had three components: (i) an aircraft campaign using the NASA DC-8 and ER-2 airplanes out of Kiruna/Sweden, (ii) launches of large stratospheric research balloons from Kiruna, (iii) validation excercises for the commissioning phase of SAGE III. The German Arctic research station Koldewey in Ny-Ålesund/Spitsbergen contributes to (i), (ii), and (iii) by performing measurements of stratospheric components like ozone, trace gases, aerosols (PSCs), temperature and winds. The measurement results were transmitted quasi online to the flight planning center in Kiruna, in order to allow a better directing of the air plane flights. In addition the Koldewey-Station has been designated a validation anchor site for the SAGE III validation. The activities are organized within a NASA accepted proposal of ground-based validation support by the NDSC Primary Station at Ny-Ålesund, Spitsbergen and by a SAGE III validation working group for Ny-Ålesund. The main observation periods are from December 1999 to March 2000.

In order to get detailed vertical ozone profiles above the range of standard electrochemical ozonesondes (typically 35 km), a radiosonde together with an optical ozonesensor is launchend with a special plastic foliage balloon. The balloon payload consists of a digital radiosonde (DFM 90) using GPS for altitude measurements and a two channel filter spectrometer (optical sensor) to measure the vertical ozone distribution up to more than 40 km altitude. The ozone profiles obtained by the optical sensors will be compared with ground-based microwave and lidar ozone observations as well as with the standard balloon-borne ozone measurements with electrochemical ozone sensors.

The aim of the project is to study the properties (radiative effects, composition) of aerosols using FTIR emission spectroscopy. To determine seasonal changes in aerosol properties the measurements will be carried out year round on a weekly schedule.

The current scientific knowledge does not allow estimating accurately the surface radiative forcing caused by tropospheric aerosols and their influence on the evolution of the Earth climate. The radiative forcing depends on the optical properties of the aerosols at solar and thermal infrared wavelengths. These optical properties depend, in turn, on the chemical composition and size of the aerosols. Remote sensing with passive radiation sensors operating in the above-mentioned spectral ranges allows to measure the optical properties of the aerosols and to characterise their temporal variability. These data are needed for regional climate simulations of the Arctic, particularly for delineating the impact of the Arctic haze phenomenon. In this project, a synergetic effort will be made to obtain information about the radiative and microphysical properties of springtime arctic aerosols. Therefore, a polarisation-spectrometer for the solar spectral range, which is currently developed at the Free University of Berlin as a variant of the FUBISS spectrometer, will be operated from the surface in coincidence with the Fourier Transform InfraRed-spectrometer (FTIR) installed at Ny-Aalesund by the AWI. The former instrument measures the intensity and polarisation of the scattered solar radiation from the visible to the near-infrared. The latter measures the radiation emitted by the Atmosphere itself in the thermal infrared window region. Together, they thus provide a wealth of information about the aerosol optical properties at the interesting wavelengths (spectral optical depth, single-scattering albedo, and asymmetry factor of the phase function), which will allow inferring the aerosol microphysical properties. Complementary measurements of the aerosol microphysical properties will be provided by an aerosol volatility analyser, which is maintained by the University of Leeds and will also be brought to Ny-Aalesund. This instrument comprises a fast response scanning volatility system and an optical particle counter. From the thermal response of the aerosol number and the change in the size distribution conclusions can be inferred about the chemical composition and the state of mixing of aerosols as a function of size.

Aim of the project is to develop a cost-effective long-term European observation system for halocarbons and to predict and assess impacts of the halocarbons on the climate and on the ozone layer. Beside the routine observations within the NDSC it is planned to perform with FTIR (Fourier Transform Infrared Spectroscopy) absorption measurements of CFCs (e.g. SF6, CCl2F2, CHF2Cl) and related species on much more observation days.

The aim of the project is to perform solar and lunar absorption measurements of atmospheric trace gases for the valdation of the SCIAMACHY satellite. Besides the routine observations within the NDSC it is planned to perform more intense measurements, especially during the satellite overpasses.

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.

The subject is to determine the horizontal distribution of aerosol and trace gases by airborne measurements with the Gulfstream III (transarctic flight), ground based measurements in Ny Ålesund (Koldewey Station, Rabben) and satellite measurements with SAGE II / SAGE III. Objective is to get vertical and horizontal aerosol profiles, to research the trace gase variations in the Arctic and to compare remote sensing und in situ measurements.

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.

By launching several hundred ozonesondes and by ozone lidar measurements at many Arctic and sub-Arctic stations, one of them Ny-Ålesund, the stratospheric chemical ozone loss will be determined. The launches of all stations will be coordinated by analysis of trajectory calculations based on analysis and forecast wind fields. The aim is to get as many ozone sounding pairs as possible, each of them linked by trajectories in space and time. A statistical description of the ozone differencies given by the first and the second measurement of individual sonde pairs will yield the chemical ozone loss with spatial and time resolution. Four similar campaigns took place in the Arctic and in the mid-latitudes covering the time period of Januar to March in each of the last four winters. In the first three winters high ozone depletion rates (20 - 50 ppbv per day) were determined in some height levels within the polar vortex. In the height level of the ozone maximum an integrated ozone loss (during the winter) in the order of 60 % have been found. These are record ozone losses for the Arctic polar region. In the last winter the ozone depletion rates had been much lower due to moderate temperatures in the stratosphere.

The FTIR (Fourier Transform Infrared Spectroscopy) has been established as a powerful tool for measurements of atmospheric trace gases. Using the sun or moon as light source, between 20-30 trace gases of the tropo- and stratosphere can be detected by their absorption features. The analysis of the spectra allow to retrieve the total zenith columns of the trace gases. The aim of the SAMMOA project is to study the stratospheric ozon depletion during the summer time period. While the processes during winter/spring are investigated in detail the summertime ozone loss has not been studied so far. Therefore FTIR solar absorption measurements of ozone and related species are to be done on much more observation days beside the routine observations within the NDSC

Quasi-continuous observation of several atmospheric species are performed by measuring the absorption of visible and near ultraviolet sunlight scattered from the sky or in direct moonlight. Column abundance of molecules such as ozone, NO2, OClO, NO3, BrO, HCHO and IO are derived by means of a Differential Optical Absorption (DOAS) algorithm and a radiative transfer model. These activities are part of calibration and validation studies of different satellite experiments (GOME, SAGE III, SCIAMACHY). Since 1999 the instrument is part of the Network of the Detection of Stratospheric Change (NDSC). The instrument has been installed in 1995 as the second UV/vis instrument from the Institute of Environmental Physics. One similar setup in Bremen is continuously running with the exception of short maintenance breaks since 1993.

The changes in the stratospheric ozone layer due to anthropogen emissions lead to an increasing insolation of sunlight in the UV-B range (280nm - 320nm) on ground. One of the major objects of UV-B measurements is to detect long-term trends. The most interesting areas corresponding to ozone depletion are Antarctica and more recently the region around the northern pole. In interdisciplinary cooperation the data are also basis for research in the effects of increasing UV-B doses on plankton, algae, and other organisms. Since 1998 additional measurements of UV-A radiation (320-400nm) are done.

The FTIR (Fourier Transform Infrared Spectroscopy) has been established as a powerful tool for measurements of atmospheric trace gases. Using the sun or moon as light source, between 20-30 trace gases of the tropo- and stratosphere can be detected by their absorption features. The analysis of the spectra allows to retrieve the total zenith columns of the trace gases. For a few trace gases the pressure broadening of the lines allows to get additionally some information on the vertical concentration profiles. Some important trace gases cannot be detected in the IR but in the UV/VIS. This makes it useful to record the whole spectral region from the IR from about 700/cm (14 µm) to the UV at 33000/cm (300 nm).

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.

In recent years, much attention has been directed towards understandig the effects of aerosols on a variety of processes in the earth atmosphere. Aerosols play an integral role in limiting visibility, they serve as nuclei for the formation of fog and cloud droplets, they affect the earth radiative budget, and thus climate, both directly and indirectly, and they inhibit the propagation of electromagnetic radiation. The Arctic aerosols, especially Arctic Haze and tropospheric ice crystals possible have important climatic and ecological and global change implications. Since 1991 Sun photometer observations of the polar atmopheric aerosol have been performed at the Koldewey Station in Ny-Aalesund, Spitzbergen. In order to complete the coverage and quality of measurements during the polar night a high sensitive Star photometer is installed since January 1996. Both measurements, the daylight Sun photometer measurements and night Star photometer measurements will be continued.

The Baseline Surface Radiation Network (BSRN) is a cooperative network of surface radiation budget. Measurement stations operated by various national agencies and universities under the guiding principle set out by the World Climate Research Programme (WCRP). Presently about 15 stations have been established, one of them is Ny-Ålesund. The concept for a Baseline Surface Radiation Network has developed from the needs of both the climate change and satellite validation communities. The aims of the programme are the monitoring of long-term trends in radiation fluxes at the surface and the providing validation data for satellite determinations of the surface radiation budget. The BSRN station Ny-Aalesund was installed in summer 1992 and is regularly operating since August 1992.

Stratospheric aerosols like Polar Stratospheric Clouds (PSCs) or volcanic aerosols are investigated by different types of balloon borne sensors in co-operation with the University of Nagoya, Japan, and the University of Wisconsin, Laramie, Wisconsin. The sensors flown are dedicated optilca particle counters (OPC) or backscatter sondes (BKS), respectively.