Influence of the Kuroshio in the East China Sea on the baiu rainband is examined using satellite observations, a reanalysis dataset, and a regional atmospheric model from 2003 to 2008. Satellite observations and reanalysis data reveal that precipitation over the Kuroshio is the highest in early summer (June), when the baiu rainband covers the East China Sea. The high rainfall is collocated with the warm sea surface temperature (SST) tongue of the Kuroshio. This locally enhanced precipitation is embedded in the large-scale baiu rainband, so that the amplitude of precipitation over the Kuroshio is twice as large as that in its surrounding area. The Kuroshio is also accompanied by high surface wind speed, energetic evaporation, and wind convergence. This wind convergence likely results from the SST influence on atmospheric pressure through not only temperature changes, but also humidity changes. Furthermore, the Kuroshio anchors the ascent motion and large diabatic heating with a peak in the midtroposphere, suggesting that the influence of the Kuroshio extends to the upper troposphere. It is also found that the East China Sea in June is the region of the strongest deep atmospheric response to western boundary currents along with the Gulf Stream region in summer. The observational results are well reproduced by the regional atmospheric model. The model indicates that when the SST tongue of the Kuroshio is smoothed, the enhanced precipitation, the energetic evaporation, and the wind convergence over the Kuroshio disappear, although the large-scale structure of the baiu rainband is not essentially changed.

A study is made of stability properties of perturbations superimposed on an unstably stratified plane parallel flow with variable vertical shear.

An investigation is made of some features of perturbation superimposed in a plane Couette flow with unstable stratification.

A significant 4-5-day-period variation was observed in surface and aerological data obtained at the equator, 156E during November 1992. The time-height structure of the variation is determined by use of spectral and composite analysis. The 4-5-day period variation can be basically explained by westward-propagating mixed Rossby-gravity wave disturbances. However, the structure of the circulation was significantly distorted by the presence of a tropical depression. Further, two distinctive events of extremely dry air in the lower troposphere were observed. The vertical profiles of specific humidity as well as the equivalent potential temperature had distinct minima at about the 3km level. The trajectory analysis revealed that the dry-air parcels were brought from a subtropical area by tropical disturbances, especially by the intense meridional flow associated with 4-5-day period disturbances. These events of dry-air intrusion are detected in the precipitable water data derived from SSM/I satellite imageries and the zonal scale of the intrusion is estimated to be about 1000km. Convection was strongly suppressed over the dry air, and the latter was maintained to about 4 days due to very weak vertical mixing.