0509号台风(Matsa)登陆螺旋云带的增幅及其台前飑线的特征研究

Characteristic analysis of the strengthening spiral bands and the preceding squall lines in association with the 0509 Typhoon"Matsa"

利用FY-2C卫星、Doppler雷达、风廓线和加密自动站等资料,对0509号台风"Matsa"(以下简称Matsa)螺旋云带登陆过程中云、回波、风雨等时空分布特征量进行了深入的研究,对螺旋云带、飑线风雨增幅进行了定量分析。结果表明:Matsa先后有6条外、内对流螺旋云带登陆并影响中国大陆,对流螺旋云带登陆过程中增幅显著,云顶最低亮温平均下降20.2℃,螺旋云带登陆至减弱维持时间12.8 h,登陆间隔8.6 h。外螺旋云带登陆时风速增幅2.0 m/s,最大增幅4.1 m/s。同时可带来平均19 mm、最大75 mm的降水量。内螺旋云带登陆时风速增幅4.2 m/s,最大增幅9.0 m/s,最大瞬时风速达30.2 m/s,同时可带来139.6—174.2 mm、最大396 mm,1 h最大降水59.8 mm。对流螺旋云带在登陆过程中,在其前沿部位不断有台前飑线向外分离,台前飑线的回波宽度一般在5 km左右,回波梯度特大,长度从几十公里到几百公里不等,登陆时回波增幅5-10 dBz。台前飑线的移动方向与台风移动方向基本一致,移动平均46 km/h,是同时刻台风时速的2.5倍。台前飑线的形成特点为先出现双链或多链小弧弓形回波,在登陆中演绎成大弧。在速度图上,台前飑线中分布着倒V型或S型零速度线。在地面小尺度风场上,表现出具有东南与东北风向辐合线,切变辐合甚至涡旋扰动的特征非常显著。飑线过境时,风向扰动47—135°,风速增大1倍以上,地面瞬时风速平均增幅为4 m/s,最大可达10 m/s。瞬时极大风速26.4 m/s,同时可带来6.9—29.1 mm、最大90 mm的降水量。500 m以上的风速比近地面大1倍,大风区厚度可伸展至对流层上部。

The spacetime characteristics of clouds, wind, and rainfall of the landfallin g spiral bands of the 0509 Typhoon “Matsa＂ were analyzed quantitatively based o n the FY-2C satellite, Doppler radar, wind profiler and auto weather station （A WS） observation data. The analysis shows there were six outer and inner spiral bands landfalling in East China. The spiral bands strengthened obviously with the minimum cloud top black body temperature declined by about 20.2℃ on average.The time span of the spiral bands from landfall to weakening was about 12.8 h a nd the interval between landfalls of the spiral bands was about 8.6 hours. When the outer spiral bands made the landfall, wind speed strengthened by about 2.0 m/s. The outer spiral bands brought about precipitation of averagely 19 mm and 75 mm in maximum. The inner spiral bands contributed to precipitation of about 139.6-174.2 mm and 396 mm in maximum. The wind speed strengthened by about 4.1m /s evenly and 9.0 m/s in maximum during the landfall of the inner spiral bands.Several squall lines formed and separated from the front of the spiral bands during their landfall. The width of the squall lines was about 5 km with a large -gradient, and the length varied from tens to hundreds kilometer. The echo reflec tivity of the squall lines strengthened by about 5-10 dBz during landfall. The m oving direction of the squall lines was the same as the typhoon, and the moving speed was about 46 km, 2.5 times of the typhoon. The squall line appeared like a n arc with two or several chains in the radar echo, and the chains combined to b e a large arc when the squall lines made landfall. There was slow wind with an i nverse “V＂ or “S＂ shape in the radial velocity distribution of the Doppler rad ar echo. A confluence line between southeast and northeast winds appeared in the smallscale surface wind field. When the squall line passed through, the wind speed doubled and the wind direction changed by 47°-135°.It contributed to 6.9-29.1mm precipitation and 90 mm maximum precipitation. The wind speed stre ngthened by about 4 m/s on average and 10 m/s in maximum. The maximum gust speed was about 26.4 m/s. The wind speed above 500 meter height was twice of that at ground surface. The gust zone can extend into the upper levels of the troposphere.