CHARACTERISTICS OF THE SPORADIC NA LAYERS OBSERVED DURING THE AIRBORNE LIDAR AND OBSERVATIONS OF HAWAIIAN AIRGLOW AIRBORNE NOCTILUCENT CLOUD (ALOHA ANLC-93) CAMPAIGNS/

We summarize the characteristics of the 43 sporadic Na (Na-s) layers o bserved by the airborne Na density and the Haleakala Na wind/temperatu re lidars during the Airborne Lidar and Observations of Hawaiian Airgl ow/Airborne Noctilucent Cloud (ALOHA/ANLC-93) campaigns. Na-s layers a re clearly not a local phenomenon since the horizontal extents varied from approximately 25 to almost 1600 km with a mean of 440 km. For the majority of the Na-s layers observed above Haleakala, the temperature s were significantly warmer than the mean. The average enhancement was 12.9 degrees K or about 6%. The temperature variations typically led the Na-s density variations in time and on average reached their maxim um values approximately 0.7 km below and 23 min before the Na-s maxima . However, the maximum temperatures and Na-s densities were only weakl y correlated. Strong vertical shears in the horizontal winds were obse rved during the majority of the Na-s events. The average maximum total shear was approximately equal to the shear instability limit of 42 m s(-1) km(-1). The maximum shears were located on average about 0.5 km below the Na-s layer. In most cases the meridional shears were signifi cantly stronger than the zonal shears. The maximum total shears were g enerally directed to the N-NE and to the south. The strong temperature and wind perturbations observed during the majority of the events sug gest that gravity waves play an important role in Na-s formation, alth ough the exact nature of that role remains unclear.