摘要
利用济南CINRAD/SA多普勒雷达产品,针对2006年7月5日飑线天气过程,分析回波发展演变、流场结构,讨论外流边界、强下沉气流与大风的关系,分析组合反射率因子、垂直液态含水量、中气旋产品特征。结果发现,飑线过境时风速出现两个极大值,一个出现在外流边界影响时段,另一个发生在强回波下沉气流影响时段;在横槽南下过程中,飑线后部强入流不断补充,前侧暖湿气流沿着后部入流爬升,不断产生新的单体,使得风暴得以维持发展;在垂直流场结构上表现为前侧暖湿气流倾斜上升,然后主体部分向后倾斜,后部有冷空气注入,形成下沉气流,下沉气流在地面附近辐散,与前侧入流形成低层阵风锋,是造成地面破坏性大风的主要因素。在水平流场结构上表现为低层存在气流辐合上升运动,中层有气旋性旋转气流,风暴高层为辐散气流。飑线消散阶段后期中层出现MARC,带来大风天气,而同时伴有冰雹天气的风灾产生在飑线达到最强至开始减弱的时段。当回波强度≥50dBz,且垂直液态含水量≥35kg.m-2,当有中气旋时,有利于产生冰雹和大风天气;外流边界的出现,反映了强对流回波后部下沉气流较强,是灾害性大风的前兆。
By using Jinan CINRAD/SA Doppler radar products, the weather process of squall line on July 5, 2006, evolution of echo and flow structure were analyzed, the relations between the outflow boundary, sinking air currents and strong wind were discussed, and the portfolio reflectiv- ity factor, the vertical liquid water content, the mesocyclone product characteristics were ana- lyzed. The results showed that two maxima of wind speed occurred during the squall line passing, one appeared in an outflow boundary impact sessions, another in strong echo sinking airstream af- fected periods. As the transverse trough moves southward, the inflow continuously added to the rear of squall line, the warm and wet air flow climbed along the rear of inflow, which constantly created new cells and maintained the development of storm. In the vertical flow structure, the warm air for the front side was tilted upwards, and the main part tilled backwards. In the rear there was the cold air injected and the downward flow formed. The sinking air near the ground diverged, together with the lateral inflow formed the lower gust front, which was the major fac- tor causing the ground destruction. In the horizontal flow structure there was an upward motion of convergence at low level and a cyclone rotational flow at the middle level. At high-level there was a divergence flow. In the dissipating period of squall line, MARC appeared at middle level, which brought strong winds and hail weather. The wind disaster with hail produced in the period when the squall line was the strongest and began to weaken. When the echo intensity≥50dBz and vertical liquid water content ≥35 kg·m^-2, the meso-cyclone is favorable for generating of hail and strong wind. The emergence of outflow border reflected that the strong sinking flow in the rear of strong echo is a precursor of the disastrous wind.
出处
《气象》
CSCD
北大核心
2009年第3期60-65,I0007,共7页
Meteorological Monthly
关键词
飑线
流场结构
大风
中气旋
squall line flow structure strong wind mesocyclone
