Abstract
A general structure of Typhoon 9426 (Orchid) up to the lower stratosphere including the inner coreregion was observed by the MU (middle and upper atmosphere) radar on 29-30 September 1994. In thispaper, a meso-a-scale wind field and meso-β and -γ scale features of precipitating clouds in the typhoonwere investigated.The kinematic structure in the front and rear of the typhoon was quite different because of its transitionfrom mature to decaying stages and an asymmetric distribution of cloud and precipitation. In frontof the typhoon, the meso-α-scale wind field was characterized by a cyclonic rotation with the maximum atlow level, outflow regions tilted outward with height, and vertical motions affected by convection andtopography. In the vicinity of the typhoon center, the tangential wind had a vertical spiral structure forthe center, considered to be the result from deformation of the center of the decaying typhoon. In the rearof the typhoon without precipitating clouds, the cyclonic wind became weak, and the outflows and verticalmotions as seen in the front were not detected.
In front of the typhoon, an eyewall and wide rainband were observed. In the eyewall, a meso-γ-scaleremarkable updraft associated with an outflow region, considered to be a part of vertical circulation, wasfound in the upper troposhere. The outflow region tilted outward was originated from the area of maximumradial shear of the low-level cyclonic wind. It was extended to an updraft region within an upperlevelband-shaped cloud, located far from the typhoon center. The wide rainband (50-70 km width) waslocated at the outer edge of the band-shaped cloud, and it lasted in the development of the upper-levelcloud. It was accompanied by the tilted outflow region to 6 km altitude, the bottom of which was locatedat the maximum of the cyclonic wind. A narrow rainband (20-40 km width), that a lifetime was quiteshort (1.5 hours), was also observed by the boundary layer radar (BLR) at another site. An outflow regionwith the tilted structure was present in the outer part (convective portion) of the rainband, and its bottomwas not associated with strong cyclonic wind as seen in the wide rainband.
