FIRST SIMULTANEOUS AND COMMON VOLUME OBSERVATIONS OF NOCTILUCENT CLOUDS AND POLAR MESOSPHERE SUMMER ECHOES BY LIDAR AND RADAR

We present the results of first simultaneous and common volume observa tions of noctilucent clouds (NLC) and polar mesosphere summer echoes ( PMSE) by two ground-based lidars and one VHF radar. The measurements w ere performed at the ALOMAR facility (69 degrees N, 16 degrees E) duri ng the time period July 23 through August 18, 1994. Throughout this pe riod, NLC layers were observed by the lidars on four occasions. During each of these four lidar-observed NLC events, PMSE layers were also o bserved overhead by the radar. These joint NLC/PMSE events divide into two distinct types: (1) tightly coupled and (2) loosely coupled NLC a nd PMSE layers. In one of the events, the PMSE layer developed into a well-defined double layer with only 0.8-km vertical separation, while the lidar-observed NLC layer, matched closely in time and space the lo wer PMSE sublayer. Within all four NLC/PMSE layers, the wind speed inc reased sharply with increasing altitude with wind shears amounting to 0.03 s(-1) and larger. Current theories can explain some of the observ ed layer features.