Ground-based millimeter-wave observations of ozone in the upper stratosphere and mesosphere over Tsukuba

We present ground-based millimeter-wave observations of the upper stratosph eric and mesospheric ozone, conducted at the National Institute for Environ mental Studies (NIES) in Tsukuba, Japan (36 degrees N, 140 degrees E). The measurements were started in October 1995. The millimeter-wave radiometer u sed for the present study is equipped with the superconductor-insulator-sup erconductor (SIS) mixer receiver and the acousto-optical spectrometer (AOS) . Vertical profiles of ozone mixing ratio from 20 to 80 km were retrieved f rom the observed ozone spectra for 23 months from October 1996 to August 19 98 by using the weighted-damped least squares algorithm adopted for differe ntial emission. Vertical resolution is estimated to be 14 km from the avera ging kernels. The total random error on the retrieval is estimated to range from 3 to 13% in summer, and from 2 to 9% in winter, respectively, between 38 and 76 km in altitude. The ozone number density at 38 km with the radio meter which was convolved with the vertical resolution of the lidar agrees well with that of the lidar within a systematic difference of 1%, indicatin g that the millimeter-wave data at 38 km are validated by the lidar measure ments. Annual and semi-annual variations are clearly seen at 50 and 76 km, respectively, in the time series of the ozone mixing ratio observed during 23 months. The annual variation at 50 km is consistent with that in the cli matological models. The semi-annual variation at 76 km observed in this wor k is similar to that of the Solar Mesospheric Explorer (SME) data, except t hat the ozone mixing ratio in spring measured with SME is about 1.7 times l arger than that in autumn while those with the radiometer are almost same.