河源市秋季锋面暴雨的概念模型和物理量分析

利用1964—2013年河源市5个国家气象观测站日降水量和NCEP/NCAR逐日4次2.5°×2.5°再分析资料,对河源市秋季锋面暴雨进行环流分型和物理量合成分析。结果表明:河源市秋季锋面暴雨可以分为5种类型,分别为南北槽型、丁字槽型、阶梯槽型、蒙古低槽型和纬向多波动型,出现最多的为南北槽型。南北槽型、丁字槽型和阶梯槽型的主要水汽来源分别为西太平洋的东南风经南海进入华南的输送、青藏高原南侧和孟加拉湾的西南风汇合、西太平洋副高南侧东风在南海地区转向进入华南地区的输送及青藏高原南侧的西南风的输送;河源地区低层辐合、高层辐散的配置为暴雨的产生和维持提供了所需的动力条件;高温高湿的大气层结,为暴雨的形成提供有利的对流不稳定条件;与华南汛期暴雨相比,低层辐合、高层辐散及垂直速度中心的最大值均偏小,且南北槽型和阶梯槽型的温湿条件也差一些;环流分型和物理量合成分析揭示了秋季锋面暴雨产生的共同特点,为今后预报该类暴雨提供参考,但此方法同时可能会平滑部分个性特征,在分析和预报过程中,系统强弱和物理量上可能存在一定的差异。

Conceptual Models of Frontal Heavy Rain in the Autumn of Heyuan City and Analysis of Physical Quantities

Using daily rainfall data of five national meteorological stations in Heyuan from 1964 to 2013 and the 2.5°×2.5°reanalysis from NCEP/NCAR available four times daily during the same period,this paper classifies circulation patterns associated with autumn frontal heavy rain in the city and conducts a composite analysis of its physical quantities.The result is shown as follows.The autumn frontal heavy rain of Heyuan can be classified into five types,which are north-south oriented troughs(A),T-shaped troughs(B),terrace troughs(C),low troughs over Mongolia(D)or zonal multiple waves(E).Type A occurred most frequently.For the main source of water vapor,Type A was the result of a southeasterly wind transported from the western Pacific to the south of China via the South China Sea,Type B originated from the convergence of a southwesterly wind to the south of the Tibetan Plateau and over the Bay of Bengal,and Type C was caused by an easterly wind south of a suptropical high in the western Pacific diverted over the South China Sea to the south of China and a southwesterly wind south of the Tibetan Plateau.The allocation of low-level convergence versus upper-level divergence over the area of Heyuan was dynamically favorable for the generation and maintenance of the heavy rain.A warm and humid atmospheric stratification provided favorable conditions of convective instability for the heavy rain formation.Compared with the heavy rain during raining seasons in the south of China,the frontal heavy rain's maximum values of low-level convergence,upper-level divergence and vertical velocity center were smaller and its temperature and humidity conditions were also poorer for Type A and C.On the one hand,the classification of circulation patterns and composite analysis of physical quantities reveal characteristics true to all frontal heavy rain happening in autumn and are helpful in forecasting such weather in the future.On the other,there may be some differences in the intensity of weather systems and physical quantities analyzed and forecast as individual characteristics may be ignored due to smoothing.