Lidar observations of the Fe layer and temperatures in the polar mesopause region

Lidar observations of the mesospheric Fe layer and temperatures have been performed at Davis, Antarctica and ALOMAR, Norway. Large-scale transport is the primary cause of the seasonal variation of the Fe layer. An uptake of metal atoms on ice particles, as well as temperature-dependent chemistry, play secondary roles for the seasonal variation. The regular bottomside extension of the Fe layer in the upper mesosphere and lower thermosphere (MLT) is caused by the direct photolysis of FeOH. Temperature and Fe density observations reveal unexpectedly strong tidal modulations in the polar MLT