Groundbased Validation Support by the NDSC Primary Station at Ny-Ålesund, Spitsbergen

Point of Contact:     Dr. Roland Neuber
                               Alfred Wegener Institute, Research Unit Potsdam
                               Telegrafenberg A43, D-14473 Potsdam, Germany
                               Tel.: +49-331-288-2129
                               Fax: +49-331-288-2178

Location

Ny-Ålesund, on Spitsbergen, is a small Norwegian settlement focused on scientific research in the Arctic.
At 79°N, 11°E it is located about 1000 km off the North Pole and mid way on a straight line between Kiruna, Sweden, the base of SOLVE, and the Pole.
At Ny-Ålesund/Spitsbergen a Primary Site within the Network for the  Detection of Stratospheric Change (NDSC) has been established in 1992. The site  hosts state of the art instrumentation for the observation of stratospheric constituents like ozone, aerosols, and trace gases, which contribute to the  ozone chemistry. The instruments are operated on a routine basis by dedicated station personnel including scientists and engineers. Data processing occurs at  the home institutions, namely at the Alfred Wegener Institute, Research Unit  Potsdam (AWI), at the University of Bremen, Institute of Environmental Physics (iup), and at the Norwegian Institute for Air Research (NILU).
The NDSC observatory at Ny-Ålesund, a part of the German Arctic Research Station (Koldewey-Station) houses most of the instrumentation.
 

Instrumentation

Ozone Sondes

ECC 6A sondes will be launched at least twice per week on pretreated Totex rubber balloons. Expected altitude range is 0 - 30 km. Additional sondes are launched when previously probed air masses overpass the station ("Match" technique).
Meteorological radio sondes are launched every day at 12 UT.

Lidar Facility

 The lidar facility consists of two main components, the multiwavelength stratospheric ozone and aerosol lidar and the tropospheric Raman lidar for aerosol measurements.
 The stratospheric ozone- and aerosol lidar instruments comprises two lasers, a XeCl-Excimer laser for UV-wavelengths and a Nd:YAG-laser for near IR- and visible wavelengths, a telescope of 60 cm diameter and a detection systems 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. Furthermore the detector system collects the vibrational N2-Raman scattered light at up to three additional wavelengths. The above described detection system is used during the long winterly polar night with permanent darkness.  The vertical resolution is better than 100 m for the altitude range from 10 to 40 km. A major topic of the lidar facility is the measurement of PSCs.
 The tropospheric lidar system employs the same Nd:YAG laser as the stratospheric part, a dedicated 30 cm telescope, and a three channel detection system for simultaneous recording of analog and photon counting signals at 532 nm in both polarizations, and the Raman line at 607 nm. It is used to observe tropospheric aerosols between the boundary layer and the tropopause. The aerosol extinction data retrieved can be directly compared to extinction data obtained by satellite and by the local photometers.
 

Microwave Radiometer for Atmospheric Measurements (RAM)

The Radiometer for Atmospheric Measurements (RAM) [Langer et al, 1998] provides profile information on stratospheric ozone, chlorine monoxide (ClO) and water vapor. Basis of millimeter-wave radiometry is the detection of emission lines of thermally induced rotational molecular transitions.  >From the shape of the pressure broadened line the volume mixing ratio (VMR) profile of a particular molecule can be retrieved.  The measurements are self-calibrating with a good long-term stability.  Ozone profiles are retrieved from a line at 142.175 GHz, ClO profiles from a set of lines around 204.352 GHz and H2O profiles from a line at 22.2 GHz.  Since radiation at the frequencies of the ozone and ClO lines can not be amplified directly, the heterodyn principle is used.  A strong monochromatic local oscillator together with the atmospheric signal is injected to a mixer which downconverts the signal frequency to an intermediate frequency (the difference of both frequencies).  This signal can be processed by common electronic devices.  To suppress noise the mixer and the first amplifier are cooled down to 12 K.  Amplification of the H2O signal is possible without mixing and the atmospheric signal is injected directly into the first amplifier. Cooling is not necessary for the H2O branch of the instrument.  The RAM consists of three front-ends for the three different species using one back-end in a time sharing mode.  At low tropospheric water vapor content during winter/spring the ozone and ClO front-ends are in operation and for other conditions the ozone and H2O front-ends.  The back-end holds a high resolution acousto-optical spectrometer with a bandwidth of 1 GHz and a resolution of 1.2 MHz.  Ozone profiles are retrieved from two overlapping spectra giving a total bandwidth of 1.65 GHz.
 

Fourier Transform Spectrometer

 Since 1992 solar and lunar absorption spectra are recorded in the IR to measure the total zenith column densities of about 20 trace gases in the strato- and troposphere (e.g. HCl, NO2, HNO3, CO, C2H6, CFCs). The measurements are performed using a Bruker 120 HR Michelson interferometer, enabling a maximum resolution of 0.0025 cm-1. Furthermore we perform emission spectroscopy measurements to record the trace gas concentration during the polar night. Contrary to the absorption measurements the emission measurements need to be calibrated by a black body of known temperature and emissivity. Emission spectra yield the optical depth of the atmosphere in the infrared between 8 and 12 µm in addition to the trace gas concentrations. Combining the measurements in the IR with the sun and star photometer measurements in the UV gives the optical depth in the range between 300 nm and 12 µm.
 

UV-vis spectrometers

    Two different instruments will be operated from mid February onwards: a SAOZ instrument and a dedicated DOAS instrument, which follows the design of the space borne GOME instrument. Both set ups record O3 and NO2 columns using the Differential Optical absorption technique. The later instrument from Univ. of Bremen is also able to detect BrO and enhanced levels of OClO. The SAOZ is operated by NILU.
 

Photometers

    Two types of photometers are operated in order to derive the total aerosol optical density. During winter a 7 wavelength channels star pointing instrument records the direct stellar radiation from two stars of different elevation. During summer (i.e. from March onwards) an automated 18 channel instrument measures the solar radiation in the spectral range form 350 nm to 1050 nm.
 

Objectives

Operating Institutions

Alfred Wegener Institute (AWI), Research Unit Potsdam (Germany) maintains the German Arctic Research Station (Koldewey-Station) in Ny-Ålesund. It operates the ozone sondes, lidars, FTS, and photometers. AWI coordinates the SOLVE activities in Ny-Ålesund. Another topic is the "Match" coordination and analysis of all Arctic ozone sonde launches during winter 1999/2000.
The University of Bremen, Institute of Environmental Physics, operates the microwave RAM and the DOAS UV-vis spectrometer.
The Norwegian Air Research Institute NILU runs the SAOZ instrument.