热带气旋远距离暴雨的研究

A study on the mechanism of the tropical cyclone remote precipitation

  • 摘要: 用中国国家气象信息中心整编的1971—2006年中国693个地面基准站日降水资料、同期美国JTWC最佳路径资料和NCEP/NCAR再分析资料,对热带气旋(TC)远距离暴雨进行统计分析和诊断研究。结果表明:36 a中有14.7 %的TC产生远距离暴雨。TC远距离暴雨事件遍及中国大陆27个省(市、自治区),其中,环渤海地区和川陕交界处为中国TC远距离暴雨高发区。远距离暴雨集中发生在6—9月。34.6 %的TC远距离暴雨具有影响范围广、降水强度大的特点。诊断分析表明,TC远距离暴雨能否产生的关键在于热带气旋东侧环流能否将水汽输送到中纬度槽前,如果有高气压或偏北气流对水汽输送的阻断,就不会形成远距离暴雨。

     

    Abstract: Based on CMA 24 h precipitation data, JTWC’s best track data set of tropical cyclones and the NCEP reanalysis data, the mechanism of the Tropical Cyclone Remote Precipitation (TRP) has been discussed. The statistical analysis shows that 14.7% tropical cyclones could produce the TRP events (TRPs) in 1971-2006. Majority of the events would last more than two days. A number of TRPs have the feature of wide distribution and high rainfall rate. High frequency of TRPs occurs in July and August. The statistical analysis also shows that there are two areas with the high frequency of TRPs, i.e, the area of encircling Bo Hai Sea (region Ⅰ) and the juncture area between Sichuan and Shaanxi provinces (region Ⅱ). The diagnostic study with inter-comparison between the two group data of TRPs and Non-TRPs indicates that the prominent differences in lower levels either in region Ⅰ or Ⅱ lay in that there exists the typhoon interaction with a westerly trough in TRP group and without a westerly trough in Non-TRP group but with the dry northwesterly flow instead. More over, it is found that tropical cyclones with TRP have strong southeast wet flow channel connected and Non-TRP cyclones without such channel. Obvious differences are also appeared in the upper level. In region Ⅰ, the jet stream is located to the north of the remote rainfall region, and it incurs the divergence and ascending motion for TRP. However, the upper level jet stream covers the region and induces the descending motion in the same region for Non-TRP. Similar results are showed in the region Ⅱ. The composite data analysis of the moisture fluxes budget in region Ⅰ and Ⅱ shows that tropical cyclones with TRP can transport moisture to reach the region Ⅰ and Ⅱ and moisture transport form the cyclones without TRP is restricted only in a local area. The moisture increases remarkably form the area of TRP. On the contrary, moisture decreases obviously in the same area without TRP. Moisture transport of a tropical cyclone plays an important role in TRP.

     

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