Handout (1.8 MB)
At low levels (from 2 to 3 km altitudes) of the eyewall, those were sufficiently below the 0 °C level (5.7 km altitude), differential reflectivity (Zdr) increases with radar reflectivity (Zhh). The maximum value of Zdr is approximately 1 dB. This indicates that the long-axis direction of raindrops in the lower parts of the eyewall is averagely near horizontal even in the region of horizontal gale wind of 60 m s-1 or more.
Around the 0 °C level, layers of low correlation coefficient between horizontal and vertical polarization signals (ρhv) were observed in a large area of the eyewall, which indicates the existence of melting layers. However, the levels of the low-ρhv layers in the eyewall are generally higher than those in surrounding areas, and rise up to 2 km. Hydrometeor-type classification was conducted using a fuzzy logic scheme. Around the highest echo-top area in the eyewall, a wet graupel region is found around the 0 °C level with the region of dry graupel overlying this. The low-ρhv layer in this region corresponds to the upper part of the wet graupel region. On the basis of these results, the microphysical structure of the eyewall of the mature typhoon is discussed.
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