DIURNAL AND SEMI-DIURNAL TEMPERATURE VARIABILITY OF THE MIDDLE ATMOSPHERE, AS OBSERVED BY ISAMS

Some preliminary results are presented showing that the ISAMS instrument on board the UARS satellite has detected sun-synchronous variations in atmospheric temperature between 15-80 km altitude. These are interpreted as the westward-migrating diurnal and semi-diurnal tides. Zonal mean maps of the amplitudes of these components are shown, determined from 40 days' observations during the northern hemisphere winter of 1991/92. The results show maximum amplitudes approximately 5 K, with the diurnal tide strongest over the equator while the semi-diurnal tide is strongest at mid-latitudes. Comparisons are made with previous observations from the LIMS instrument and the lidar at Biscarrosse, France. While the ISAMS and LIMS results are consistent, several significant differences from the lidar results are noted. The conclusion is that information on the global diurnal and semi-diurnal temperature tides in the middle atmosphere may be obtained from a relatively simple treatment of ISAMS data.