We report about observations of meteor trails by ground-based lidars which were obtained with two metal resonance lidars monitoring simultaneously the same air column at meteor trail heights. The lidars are located at the site of the Leibniz-Institute of Atmospheric Physics (54 deg N, 12 deg E). More specifically, we have used K and Ca lidars to study meteor trails with respect to (1) their absolute K or Ca abundances, (2) their duration in the laser beams, (3) the altitude distributions of the K and Ca trails, and (4) the reaction of the regular K and Ca layers to the occurence of a (yet unknown) meteor shower. Lidar observations during the night of March 6-7, 1997, began around 1820 UT. They indicated the start of an unknown meteor shower at approx 2200 UT, which we could observe until 0430 UT of March 7. Within 4 h after 2200 UT, the column densities of the regular K and Ca layers increased by factors of 2 and 4, respectively. During the period of the shower, our lidars registered 26 Ca trail events, but only 2 K trail events. Hence we observe for the two metals a noticeable difference between their column density enhancements and rates of trails. The rate of Ca trails was quite similar to that observed by our lidars near the peak of the Lyrids on April 22-23, 1997. The Ca trails were observed in the altitude range from 81 to 98 km with a mean altitude of 89.6 km. In all of the lidar-observed meteor trails, it was either K or Ca which could be detected. Metal densities in the trails ranged from approx 90 to 360 cm~(-3) in the case of K and from 50 to 2700 cm~(-3) for Ca.
展开▼
