Studies on the density and formation mechanism of the solid PSC particles in the Arctic stratosphere

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In the winter 2003/2004,the lidar observations were started at Ny-Aalesund in the end of December when the temperature in the Arctic stratosphere began to be lowered. We prepared the OPC for the balloon launching, and waited the good timing for the PSC observation. PSCs were not observed in this winter because the stratospheric temperature had not been lowered enough for the formation of PSCs from December through January. However, we observed layer of increased depolarization layer (layer of solid particles) in the altitude around 35 km from the beginning of December. The temperature at this altitude is higher than the evaporation temperature of the background sulfuric acid aerosols. The similar layer was also observed in the winter of 2000/2001. Although the origin of this layer were assumed to be as rocket exhausts or meteor smoke, etc., it has not been identified, yet. The radius of the solid particles was though to be relatively small, or about 0.05 μm. Since this kind of small particles are suggested to be potential nuclei of solid PSCs, the data were quite useful for this study.In the winter 2004/2005,we continued observation from the end of November through the beginning of January. The stratospheric temperature has been lowered lower than the PSC formation temperature since the end of December. We could get the data especially when the PSCs start to appear in the end of December by lidar and OPC. We are now examining the data.