Yoshiaki Shibagaki

Rain Attenuation Characteristics of Ku-Band Satellite Signals Related to Radar Observations of the Wind Velocities at Rain Height

[Abstract] Ku-band satellite signal levels have been simultaneously observed at Osaka Electro-Communication University (OECU, Neyagawa, Osaka), the Research Institute for Sustainable Humanosphere (Uji, Kyoto) and the Shigaraki MU radar observatory (Koga, Shiga) of Kyoto University since September 2002. The speed and direction of rain area motions are estimated from the time differences in the attenuation detected at these three locations, and compared with the wind velocity (speed and direction) measured by the MU radar at the rain height. As a result, the wind velocities at the height of 2-6 km are shown to agree well fairly with those of the rain area motions detected on the ground. The wind speeds, in general, tend to become larger as the height increases. Also, the wind directions approach eastward in higher altitudes in the case of cold fronts.

Horizontal variations of gravity wave activities in the lower stratosphere over Japan: A case study in the Baiu season 1991

Vertical wavenumber spectra are analyzed by using temperature, zonal wind and meridional wind data obtained with MU radar and radiosondes at the MU observatory in Shigaraki and with operational rawinsondes at five stations over Japan. The temperature and meridional wind spectral power densities of the dominant gravity wave increase with a decrease of latitude, whereas the zonal wind spectral power seems to have a maximum near the tropopausal jet stream axis. An analysis technique to estimate a characteristic value of intrinsic frequency from the wind and temperature vertical-wavenumber spectra is proposed. The different meridional distributions of spectral power densities for temperature, zonal wind and meridional wind possibly can be explained by a latitudinal distribution of the characteristic intrinsic frequency.