Results of the 1998 Ny-Alesund Ozone Monitoring Intercomparison

The Ny-Alesund Ozone Monitoring Intercomparison (NAOMI) took place at Ny-Al esund, Spitsbergen (78.92 degrees N, 11.95 degrees E), from January 20 to F ebruary 10, 1998, This paper focuses on comparing stratospheric ozone profi les measured by the Alfred Wegener Institute differential absorption lidar (AT;VI DIAL), in routine Network for Detection of Stratospheric Change (NDS C) operation at Ny-Alesund, the mobile Goddard Space Flight Center DIAL (GS FC DIAL), the University of Bremen microwave radiometer (mu Wave), and elec trochemical concentration cell (ECC) ozonesondes, flown routinely by AWI, B elow 30 km the two DIALs and the ECC sondes give virtually the same results , with instrumental precision (repeatability) better than +/-5% and no dete ctable bias. When their coarser altitude resolution is not accounted for, t he mu Wave data show 15% low bias at 16 km and 15% high bias at 23 km, Cons iderably better agreement, better than +/-5% around 20 km and above 30 km, is found when the altitude resolution of the other data is degraded to matc h that of the mu Wave. During NAOMI the mu Wave data show high bias of up t o 10% in a mixing ratio plateau around 25 km. Such bias has not been seen i n routine intercomparisons between mu Wave and ECC sonde data at Ny-Alesund . It is likely caused by an a priori profile 40% higher than the true profi le during NAOMI, Above 30 km the mu Wave data show the best precision (repe atability), about +/-3 to +/-5%. Precision of the GSFC DIAL data decreases from better than +/-5% at 30 km to about +/-10% at 40 km, and the precision for the AWI DIAL data decreases from better than +/-5% at 30 km to +/-30% at 40 km. From 34 to 38 km the AWI profile is 12% lower than the GSFC profi le. AWI DIAL measurements that are low at 35 km often end below 40 km of sh ow high values at 40 or 45 km, This behavior seems related to the way in wh ich the AWI processing algorithm changes altitude resolution for data with poor signal-to-noise ratio.