First mesopause temperature measurements using sodium lidar observations in the Antarctic region

Abstract

The mesopause temperature structure was observed using a sodium temperature lidar system at Syowa Station (69°00\u27 S, 39°35\u27 E), beginning in February 2000. The laser transmitter was newly developed and included two injection-seeded Nd: YAG lasers. Regular observations were performed using the two-frequency technique as demonstrated by C.Y. She et al. (Geophys. Res. Lett., 17, 929, 1990), with a spatial resolution of about 1 km and a temporal resolution of 6 min. The temperature structures of the 85km to 105km region of the upper atmosphere were measured by Na D_2 Doppler profile-fitting as well as the two-frequency technique. Temperatures derived from the two techniques agreed well and were consistent with the MSIS 90 model temperature structure. Night-time temperature variations over a 15-hour period were measured in May 2000. A large temperature fluctuation with an interval of about 4 hours, and an amplitude of 60 K (probably caused by gravity waves) was observed. From the average night temperature profile, the mesopause was determined to be located at 102km, and have a temperature of 180K. These values are similar to winter values observed in the northern hemisphere