相似台风“纳沙”和“海鸥”在雷州半岛产生的降雨差异及其可能机制研究

Rainfall Difference on Leizhou Peninsula Between Similar Typhoons Nesat and Kalmaegi and Their Possible Mechanisms

关键词:  雷州半岛  相似台风  降雨差异  影响机制  台风环流

Key words:  Leizhou Peninsula  similar typhoon  rainfall difference  impact mechanism  typhoon circulation

摘要:

利用常规气象站点观测资料、区域自动气象站观测数据、雷达数据和ERA5再分析资料，对两个相似路径台风“纳沙”(1117)和“海鸥”(1415)在广东雷州半岛(LP)产生的降雨特征差异及可能机制进行研究。结果表明：“纳沙”过程降雨量和最大降雨量分别是“海鸥”的 1.5倍和 2.4倍，其中“纳沙”过程降雨量分台风环流降雨和台风槽降雨两个阶段，而“海鸥”仅有台风环流降雨。这主要因为“纳沙”登陆后，南亚高压和副热带高压断裂为东、西两部分环流，LP地区高空维持强辐散，低空西南气流和东南气流汇合为偏南风急流，同时锋区引导冷空气从 850 hPa 以下入侵到“纳沙”台风槽内，斜压效应加剧对流发生，并且在其台风环流影响减弱后，LP 地区低层辐合再次加强，进而形成降雨产生的有利条件，促使台风槽降雨增强。而“海鸥”台风登陆后，受南亚高压和副热带高压主体加强南压影响，且在台风环流减弱后，LP地区低层迅速由辐合转为辐散，下沉气流抑制对流发展，从而导致台风槽降雨难以形成。此外，还发现 LP 地形对台风降雨中心落区有一定影响，降雨中心易出现在 LP三个高峰南侧迎风坡。结果对于影响LP的台风降雨预报与诊断具有一定参考意义。

Abstract:

This study examined the differences in rainfall characteristics and possible mechanisms behind such differences for two typhoons, Nesat (1117) and Kalmaegi (1415), which followed similar paths over the Leizhou Peninsula (LP). Utilizing data from conventional meteorological stations, regional automated weather stations, radar observations, and ERA5 reanalysis, the present study analyzed the distinct patterns of rainfall induced by these typhoons. The results showed that the total rainfall and maximum rainfall of Typhoon Nesat were 1.5 and 2.4 times higher than those of Typhoon Kalmaegi, respectively. The total rainfall of Typhoon Nesat included both rainfall from the typhoon circulation and the typhoon trough, while Typhoon Kalmaegi only had rainfall from the typhoon circulation. The major reasons for such differences were as follows: after the landfall of Typhoon Nesat, the South Asian High and the Subtropical High broke into the eastern and western parts, resulting in a strong high-level divergence over the LP area, and the southwesterly and southeasterly currents converged into the southerly at the low level. Meanwhile, the frontal area facilitated the intrusion of cold air from 850 hPa and below into the typhoon trough of Typhoon Nesat, and the baroclinic effect intensified convection. After the weakening of the typhoon circulation, the low-level convergence in the LP area strengthened again, which in turn created favorable conditions for rainfall and led to the intensification of rainfall in the typhoon trough. By contrast, after Typhoon Kalmaegi made landfall, the LP region was affected by the enhancement and southward movement of the South Asian High and the Subtropical High, and the low-level convergence in the LP area quickly changed to divergence after the weakening of the typhoon circulation. The downward airflow inhibited the development of convection, resulting in minimal rainfall formation in the typhoon trough. Moreover, it was also found that the topography of the LP affected the location of typhoon rainfall centers, which were usually identified on the windward slopes southeast of the LP’s three peaks. These results may facilitate the forecasting and diagnosis of typhoon rainfall affecting the LP.