阳江市暖区暴雨的天气学分型

Classification of Synoptic Patterns for Warm-Sector Rainstorms in Yangjiang City

采用常规气象资料、区域自动站资料、NCEP/NCAR再分析资料和OLR日平均资料,对2003—2012年阳江市29次暖区暴雨过程按切变线型、低涡型和分别出现在南海夏季风爆发前后的南风型进行分型,并对4类暖区暴雨的平均环流场和个例进行分析,结果表明:(1)阳江暖区暴雨多为南风型,主要发生在南海夏季风爆发之后;(2)各类暖区暴雨环流相同点:高层受南亚高压影响,有较强辐散;低层南支槽影响明显,有低空急流向暴雨落区上空输送充沛的暖空气及不稳定能量,使中尺度对流云团生成或输入;(3)切变线型、低涡型和南海季风爆发后的南风型暖区暴雨中,暴雨发生时副高位置偏东、强度偏弱,并略有西伸或东退,处于南海季风槽活跃时期;(4)在南海季风爆发前的南风型中,副高位置较西,强度较强,强盛的西南风与副高位置偏西有关。

Using data from conventional means, regional automatic weather stations, NCEP/NCAR re- analysis and daily OLR averages, we classified 29 processes of warm-sector rainstorm in the city of Yangjiang for 2003 -2012 based on the patterns of shears and vortexes as well as southerly winds before and after the onset of the summer monsoon in the South China Sea, and analyzed the mean circulation fields and cases of the four types of warm-sector rainstorms. The results are shown as follows. （ 1 ） Mostly of the pattern of southerly winds, the rainstorm of Yangjiang mainly occurs after the onset of the summer monsoon. （2） The common feature of these patterns of rainstorm is that the upper level is affected by the South Asia high with intense divergence, a low-level southern branch of the westerlies is active and low-level jet streams supply a- bundant amount of warm air and unstable energy to the area of the rain to result in the generation or migra- tion of mesoscale cloud clusters. （3） For the warm-sector rainstorm of the patterns of shear, vortex and southerly winds after the monsoon onset, the subtropical high is more eastward and weaker or even extends more westward or retreats more eastward, as a monsoon trough is active over the South China Sea. （4） For the pattern of southerly winds prior to the monsoon onset, the subtropical high is more westward and stronger, and a strong southwesterly wind is associated with a more westward located subtropical high.