ALBERT

Description: An intercomparison campaign for Lidar measurements of stratospheric ozone and aerosol has been conducted at the Primary Station of the Network for the Detection of Stratospheric Change (NDSC) in Ny-Alesund/Spitsbergen during January-February 1998. In addition to local instrumentation, the NDSC mobile ozone lidar from NASA/GSFC and the mobile aerosol lidar from Alfred Wegener Institute (AWI) participated. The aim is the validation of stratospheric ozone and aerosol profile measurements according to NDSC guidelines. This paper briefly presents the employed instruments and outlines the campaign. Results of the blind intercomparison of ozone profiles are given in a companion paper and temperature measurements are described in this issue.

Description: During January and February, 1998, a measurements campaign was held at the Network for the Detection of Stratospheric Change (NDSC) Arctic site at Ny-Alesund (78.9N). Lidar measurements of ozone, temperature and aerosol parameters were made along with balloon sonde and microwave measurements of ozone. Atmospheric temperatures were measured between 10 and 70 km. During the time of the campaign an strong warming occurred at the stratopause, elevating the measured temperature by as much as 80 K. The height of the stratopause descended at this time to below 40 km.

Description: Worldwide, about ten Differential Absorption Lidars are used for long-term monitoring of stratospheric ozone. These systems are an important component of the Network for the Detection of Stratospheric Change. Although DIALs are self-calibrating in principle, regular intercomparisons with other ozone-lidars, microwave radiometers or ozone-sondes are highly desirable to ensure high data quality at a well known level. The Network for the Detection of Stratospheric Change (NDSC) validation policy suggests that such intercomparisons be "blind", meaning all participants submit their data to an impartial referee, without seeing results from the other participants. Here we report on the "blind" intercomparison taking place from January 20th to February 10th 1998 at Ny-Alesund, Spitsbergen (78.92 deg N, 11.95 deg E). Participating groups were from the Alfred Wegener Institute, Potsdam, operating the NDSC DIAL system at Ny-Alesund, from the University of Bremen operating the NDSC microwave radiometer for ozone profiling at Ny-Alesund, and the NASA Goddard Space Flight Center group with the "NDSC travelling standard" STROZ-LITE. The first author acted as the impartial referee. Also used for the intercomparison were data from ECC-6A/Vaisala RS80 ozone sondes routinely launched at Ny-Alesund by the AWI group. A 1% KI solution (3 ml) and the 1986 ECC pump correction (1.092 at 5 hPa) are used. The ECC-data were available to all participants during the campaign and thus were not "blind". Table 1 summarizes the expected performance of the instruments participating in the ozone intercomparison reported in this paper.