摘要
2005年第9号台风麦莎登陆后减弱为热带风暴,受其影响,8月8—10日河北东部地区出现大暴雨天气过程。采用中尺度数值模式MM5对这次过程进行了模拟,对模拟结果进行了综合分析。结果表明:暴雨区上空有准饱和且深厚稳定的湿层,低层强烈辐合与高层辐散互相配合,强降水区与散度和垂直上升中心有很好的对应关系;台风东部暖、西部冷,中低层偏东风急流将海洋上的高能量暖湿空气向暴雨区输送;局地螺旋度的极大值中心对未来强降水区有一定的指示作用,强降水区发生在风暴相对螺旋度的大值中心或其东南部的等值线密集区域。
A heavy rain occurs in east Hebei during August 8-10, 2005. It is caused by a tropical storm which is resulted from the weakened typhoon Matsa. Mesoscale numerical model MM5 V3 is used to simulate the case. The precipitation time and intention as well as the synoptic situations are compared with the observation. Similarities are found. Based on mesoscale numerical model products, the physical mechanisms of the heavy rain are analyzed. The results show that the water vapor on low-level is quasi-saturated and the humidity layer is deep and stationary during the heavy rain. There are upper-level atmosphere divergence and the low-level atmosphere convergence over the rainstorm area, and they result in strong ascending motion which is the dynamical mechanism of the initiation and maintaining of the heavy rain. The meso- and low-level air circulation and the θe field are analyzed. Results indicate that the thermal structure of typhoon is asymmetry. Its eastern region is warm and the western is cold. The strong easterly low-level jet sustains in north of the typhoon. Energy and warm vapour are transported toward the rain-storm area. In meso- and low-level troposphere the values of helicity over the rainfall center are always positive. The precipitation center is corresponding with the maximum helicity center, and its movement follows the maximum helicity center. The maximum helicity center has certain designation function for the center of the heavy rain in the future. The values of local helicity are large probably because of the large horizontal wind velocity or the horizontal vorticity or of the both. Abnormity of air is lead to, and so is the rainstorm. The results also indicate that the rainstorm occurs in the maximum SRH （storm relative helicity） center or in its southeast isoline denseness area. At the same time, the values of SRH in the rainstorm area always exceed 120 m^2/s^2 before or during the heavy rain. It means that the rotary environment wind field is advantageous to strengthen ascending motion.
出处
《应用气象学报》
CSCD
北大核心
2008年第2期209-218,共10页
Journal of Applied Meteorological Science
关键词
麦莎台风
冀东大暴雨
风暴相对螺旋度
typhoon Matsa
heavy rain in east Hebei
storm relative helicity
