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

Some preliminary results are presented showing that the ISAMS instrume nt on board the UARS satellite has detected sun-synchronous variations in atmospheric temperature between 15-80 km altitude. These are inter preted 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 1 991/92. The results show maximum amplitudes approximately 5 K, with th e diurnal tide strongest over the equator while the semi-diurnal tide is strongest at mid-latitudes. Comparisons are made with previous obse rvations 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 i n the middle atmosphere may be obtained from a relatively simple treat ment of ISAMS data.