台风“尼伯特”和“莫兰蒂”造成的江西暴雨中干空气的影响对比分析

应用常规资料、FNL再分析资料,分析相似路径台风“尼伯特”和“莫兰蒂”对江西暴雨的影响,结果表明:1)“尼伯特”和“莫兰蒂”进入江西后降水落区差别较大,“尼伯特”降水主要位于赣南地区,以对流性降水为主;“莫兰蒂”降水主要集中于赣东北,以层状云稳定性降水为主。2)“尼伯特”和“莫兰蒂”环流形势类似,台风东、西、北三面都被高压控制,台风的北侧系统差异造成两个台风移速差异,“莫兰蒂”北侧有西风槽东移,使“莫兰蒂”的移速较“尼伯特”更快。3)干空气对不稳定能量积累起重要作用,相较于“莫兰蒂”,“尼伯特”过程中江西上空有较为深厚的干空气,更利于不稳定能量积累,造成降水性质差异。4)两个台风期间高、低层干空气的差异是造成降水位置差异的主要原因。“尼伯特”期间台风西侧高层干侵入不明显,而在“莫兰蒂”期间台风西侧干侵入明显,利于江西东北部降水,而抑制江西西部南部降水;对流层低层,“尼伯特”影响期间,干空气控制台风北侧和西南侧环流,切断其西南部的水汽输送;而在“莫兰蒂”影响过程中,台风中心北、西、南侧均受干空气影响,水汽输送通道更为不通畅。

Comparative Analysis of the Influence of Dry Airs in the Typhoon Rainstorms of Nepartak and Meranti in Jiangxi Province

Based on the conventional data and the FNL reanalysis data,the effects of similar-path typhoons Nepartak and Meranti on the rainstorm in Jiangxi province are analyzed.The results show that:1)The rainfall areas of Nepartak and Meranti were greatly different after they moved into Jiangxi.The rainfall area of Nepartak was mainly located in south of Jiangxi,belonging to convective precipitation,while the rainfall area of Meranti is mainly in the northeast,being stratiform cloud stable precipitation.2)The circulations of the two typhoons were similar.They were surrounded by high pressure systems in three directions but the different systems in the north created their difference in moving speed.Affected by the westerly trough in the north side,Meranti moved faster than Nepartak.3)Dry air usually plays an important role in the accumulation of the unstable energy.There was a deep dry air layer in the upper air of Jiangxi during the process of Nepartak,which helped the accumulation of unstable energy and resulted in the different property of precipitation.4)The main cause for the different rainfall areas of two typhoons was the different dry airs in upper and lower troposphere.The high-level dry air intrusion in the west side was not obvious during of the process of Nepartak.However,when Meranti was active,the upper dry intrusion in the west side was significant,favorable for the rainfall in northeastern Jiangxi but inhibiting the rainfall in western and southern Jiangxi.In lower troposphere,during the influence of“Nepartak”,the dry air controlled the circulations on the north and southwest sides of the typhoon and cut off the water vapor transport in the southwest,while during the process of Meranti,the north,west and south sides of the typhoon center were impacted by dry air,making the water vapor transport channel even more obstructed.