No abstract

Two ground-based Doppler radars have been used to examine the wind fields and the internal structure of the rainband of Typhoon 8305. The rainband is located 300km to the northeast of the storm center and is embedded in a broad stratiform precipitation region.The air flow around the rainband is nearly two-dimensional along the rainband. Composite crosssections in the radial direction from the storm center reveal the secondary circulation associated with the rainband. A convergence zone with a large outward tilt exists from the inner edge of the rainband (the edge near the storm center) at lower levels to the outer edge at middle levels. Frictional inflow air at lower levels rises at the inner edge of the rainband and a mesoscale updraft of 2m s-1 forms. A mesoscale downdraft less than 1m s-1 exists in the maximum reflectivity zone outside the updraft zone. The downdraft is thought to be produced by the drag forces and evaporation of raindrops. The convergence between the relatively cold air associated with the downdraft and the low-level warm inflow relative to the storm center produces the updraft. This cloud dynamic mechanism is thought to play the main role in maintaining the rainband.

The structure of the rainbands and eyewall of Typhoon 8514, which landed at the central region of Japan on 30 August 1985 was observed by two ground-based Doppler radars. The main purpose of the present study is to describe a general view of the structure of the typhoon using data of the dual-Doppler radar.Although the typhoon was a small and weak typhoon, it retained the characteristics of tropical cyclones: it was accompanied by spiral rainbands (an outer rainband and an inner rainband) and had a warm core in its upper part.The outer rainband was a spiral band located about 150 km from the center of the typhoon. This rainband consisted of continuous stratiform clouds and scattered convective clouds. A radar "bright band" was observed in this rainband. Wind perturbation induced by cooling-by-melting was observed just below the bright band. An updraft of 1.5 ms-1 was produced, mainly owing to the convergence of a southeasterly flow on the inner edge of the outer rainband. This updraft maintained the outer rainband.The inner rainband was a convective spiral band located *60 km from the typhoon center. The distribution of reflectivity and vertical velocity of this rainband indicated that an old echo cell existed in the inner part, while young echo cells existed in the outer part of this rainband. An inflow (the airflow toward the typhoon center) was observed in the lower layers of the inner rainband. This inflow reached the inner edge of the young cells, and produced an updraft there. When the depth of this inflow layer became thinner, the inner rainband decayed. This indicates that the inflow had an important role to play in maintaining the inner rainband.Because the flow into the eyewall of the typhoon in the lower layers was weak, the radius of maximum wind (RMW) was located at the outer side of the axis of reflectivity maxima. The eyewall decayed when it moved to the inner area (nearer the typhoon center) of the RMW, where downdraft was predominant.

This paper describes the internal structure of two convective snowbands, deduced by using mainly single-Doppler radar data, which developed over the Sea of Japan in winter, traveled nearly perpendicularly to their orientation, and showed common features.A typical snowband was formed in a convective mixed layer 4km deep over the relatively warm sea surface in the early stage of a cold-air outbreak. This snowband was a multicell system which contained two or three echo cells in a vertical plane normal to its orientation. Each echo cell developed aloft in the forward portion of the snowband and became a mature echo cell in the middle of the snowband. The upper portion of old cells remains in a small anvil with low reflectivity below the stable layer in the rear part of the snowband. The snowband had the main updraft in its forward portion. The updraft tilted upshear and penetrated the stable layer above the convective mixed layer. There was a descending current from rear to front relative to the snowband in the lower half of the anvil. Snow particles evaporated in the downdraft. The leading edge of the downdraft was observed on the ground as a gust front with a severe gust and a drop in temperature of *1*.The circulation and maintenance mechanism of the convective snowbands was similar to those of tropical and midlatitude squall lines.

A rainstorm occurred over the central part of Japan (*36*N/140*E) within Typhoon 8124 (Gay) for 22-23 October 1981 and it was studied mainly using Doppler radar data. The main purposes of the present study are to clarify the structure of the rainstorm and to know whether it was a typhoon spiral band or another type of precipitation system.The typhoon was under transformation into an extratropical cyclone in the southeastern portion of a large-scale trough. Satellite and radar data show that this rainstorm occurred on the southeastern edge of a wide cloud band to the north of the typhoon center. The most outstanding feature of this rainstorm found by Doppler radar was the existence of a slant axis of strong wind from lower levels on the southeastern side to upper levels on the northwestern side. This means the existence of a mesoscale slant updraft. Below the axis of the slantwise updraft, convective-scale vertical motion was embeded in the mesoscale updraft. Above the axis, convective-scale vertical motion was generally small. The middlelevel air intruded into the northwestern portion of the rainstorm in the southern part. It is suggested that the intruded air was cooled by evaporation of precipitation particles and formed a mesoscale downdraft.Although a pronounced surface convergence line was associated with the rainstorm, its effect on the rainstorm was subsidiary except in the southern part.The structure of the rainstorm was partially similar to those of a typhoon spiral band, eyewall clouds and a squall line in the middle latitudes.However, this structure is considered as a characteristic feature of a rainstorm which occurs to the north of a typhoon in extratropical transition.The result and interpretation of a mesoscale budget of condensed water in the form of precipitation particles are also shown to study the relative importance of production and transport of precipitation particles in the rainstorm.