In 1995, a DOAS instrument was set-up in the NDSC building at the Ny-Ålesund (79°N, 10°E) station in Svalbard. The Ny-Ålesund station is an Arctic NDACC station with polar night from October to February, rapidly changing solar elevation angles in spring and fall and polar day in summer. The focus of the measurements at this site is stratospheric chemistry in arctic regions, in particular ozone chemistry. As a result of its geographical location, Ny-Ålesund experiences both time periods with the polar vortex located above the station, and situations when non vortex air is probed.
A second focus of the Ny-Ålesund measurements is polar tropospheric halogen chemistry, in particular bromine chemistry. Depending on the meteorological conditions, air masses from the polar ice cap are transported to Ny-Ålesund, and episodes of rapid ozone destruction in the boundary layer (low ozone events) can frequently be observed in spring.
Originally, the DOAS instrument in Ny-Ålesund was a simple zenith-viewing grating spectrometer using a 1024 pixel cooled Reticon diode array as a detector. To minimize wavelength drift, the spectrometer is temperature stabilized. Calibration measurements (line lamp, white light source) are automatically performed every day. The telescope of the instrument is integrated in a roof window, leaving all parts inside the building.
In spring 1998, a flip mirror was integrated in the telescope, facilitating alternating zenith-sky and off-axis (horizon viewing) measurements. The latter are directed towards the Fjord, and had an elevation angle of 4°. With this viewing geometry, the light path through the troposphere is strongly enhanced, increasing the sensitivity of the measurements towards tropospheric absorbers such as BrO. By combining measurements from both viewing directions, stratospheric and tropospheric contributions to the observed total column can be separated.
In spring 2002, the telescope was replaced by an improved version, allowing sequential measurements in up to 4 directions above the horizon (3°, 6°, 10° and 18°) and to the zenith with a motorized mirror. At the same time, the spectrometer and detector were replaced by a new system using a CCD detector to decrease noise at low sun.
In March 2003 a second spectrometer with a CCD was installed to extend the observed wavelength range to include the visible spectrum. Both spectrometers are connected to the same telescope.
In April 2011, the telescope was again replaced by a new version on a pan tilt head allowing measurements in various azimuthal directions, now providing measurements towards and away from the Fjord. At the same time, the UV instrument was replaced by a system with better signal to noise characteristics.
More on the instrument and measurement method can be found on our MAXDOAS page.
Some data from the Ny-Alesund measurements is available on the data products page. All stratospheric measurements from Ny-Alesund are available through the NDACC data base. If you have any other data requests, please contact Folkard Wittrock.
If you are interested in more information or would like to have access to our data, please contact Folkard Wittrock.
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