| It is well known that the thermal structure in the mesopause region (80–105km) is the result of thermal balance between solar heating, chemical reaction, and dynamical forcing throughout the atmosphere and thus affected by atmospheric solar tides, yielding diurnal (24-hour) and semidiurnal (12-hour) components. To study thermal structure, diurnal and semidiurnal tides, and seasonal variations in the mesopause region, 24-hour continuous observations over a year are required. After the first continuous temperature measurement of 34 hours in the mesopause region by using a sodium lidar system with a sodium Faraday filter [Chen et al., 1996], extensive measurements were made in February and March of 1997 as well as campaigns in 1998. The campaigns include a 24-hour continuous measurement with daytime measurements three times per month in addition to the routine nighttime measurements of five times per month.;The 24-hour continuous temperature profiles from the campaigns have been averaged over nighttime, daytime, and the diurnal cycle respectively. Significant differences, which are due to effects of the diurnal tides and can not be studied with nighttime data alone, have been seen. To study thermal structure in the mesopause region, the temperature profiles covering the whole diurnal cycle are needed; those covering only part of the diurnal cycle during either day or night are not sufficient.;With all the 24-hour continuous temperature profiles in the mesopause region, the vertical structure of the diurnal and semidiurnal tidal waves have been obtained. The amplitudes of the diurnal and semidiurnal waves can reach 10K. The phases of the diurnal and semidiurnal waves indicate that the atmospheric waves propagate upward for most of the year with wavelengths approximately tens of kilometers. A comparison of the seasonal variation of these tidal waves with the Global Scale Wave Model (GSWM) shows reasonable agreement.;Besides the operation of the sodium lidar system and the study of tides, a potassium Faraday filter was developed and tested in the laboratory. Since its properties compare favorably with the sodium Faraday filter, the daytime operation of potassium lidar system through the use of a potassium Faraday filter should be possible. |
