Arctic haze and clouds observed by lidar during four winter seasons of 1993-1997, at Eureka, Canada

A Mie-scattering-polarized Haze Lidar was installed at Eureka, Canada (80 d egrees N, 86 degrees W), in February 1993 and has been used to observe the arctic haze during winter seasons from 1993-94 to 1996-97. Although it is d ifficult to distinguish between the arctic haze and other scattering object s (mainly clouds) under the specific conditions, two methods were used to c lassify those objects into two groups. First the vertical profiles of the a rctic haze and clouds were compared with meteorological data observed by a radiosonde, and the relations between the scattering and depolarization rat ios and the meteorological data were investigated. Then, since the arctic h aze had very stable layers, the time dependency of the correlation coeffici ent between the different vertical profiles for the arctic haze and clouds was investigated. After the scattering objects were classified into two gro ups (the arctic haze and the clouds), the scattering ratio, the depolarizat ion ratio, and the occurrence probabilities of them were investigated stati stically. The statistical results, from the observations over the last four winter seasons, indicate that the average values of the scattering and dep olarization ratios of the arctic haze were respectively 1.27 and 1.34%. The average humidity over ice of the layer containing the arctic haze was 42 /- 19% (cloud: 93 +/- 13%). The arctic haze was observed at altitudes less than 3 km frequently and at altitudes of 3-5 km occasionally. (C) 1999 Else vier Science Ltd. All rights reserved.