SODIUM DENSITY AND ATMOSPHERIC-TEMPERATURE IN THE MESOPAUSE REGION IN POLAR SUMMER

Sodium lidar measurements have been performed during three summer seasons at a polar latitude (69-degrees-N), yielding profiles of sodium number density and temperature of the 85-100 km altitude region. Density measurements were performed during the months of June-August; temperature measurements only were made in August. The sodium layer was found to be both significantly weaker and more variable in summer than in winter. Measurements in summer 1987 yielded an average maximum Na density of about 900 atoms per cm3. The average maximum Na density during summer 1986 and 1988 was near 2600 atoms per cm3. The observed Na column density in summer varied from 3.10(8) to 3.10(9) atoms per cm2. Temperature measurements were performed in August of 1986 and 1987. Mesopause temperature of less than 125 K were observed in early August, rising rapidly throughout the month. The mean altitude of the mesopause was found to be about 87 km.