【摘要】 本文利用美国联合台风警报中心、日本气象厅东京区域专业气象中心和中国气象局上海台风研究所整编的热带气旋（Tropical Cyclone, TC）最佳路径数据集、NCEP大气再分析资料和相关分析等方法，研究了1989—2020年夏季（7—9月）和秋季（10—11月）西北太平洋（Western North Pacific, WNP）TC强度和频次在不同季节不同区域的基本特征及其与局地环境因子的关系，结果表明：（1）夏季WNP三个区域（Ⅰ区：10°～25°N,110°E～145°;Ⅱ区：10°～25°N,145°E～180°;Ⅲ区：25°～37.5°N,125°E～180°）TC总频次为10164次；秋季WNP 3个区域（Ⅰ区：5°～17.5°N,110°E～180°;Ⅱ区：17.5°～35°N,142.5°E～180°;Ⅲ区：17.5°～35°N,120°～142.5°E）TC总频次为4984次，夏季TC活动高于秋季。（2）夏、秋两季TC活动与850 hPa相对涡度(R_VOR)有显著的相关关系（秋季Ⅱ区除外）,除了低层R_VOR,夏季Ⅰ区TC频次与500 hPa垂直速度(O_MEGA)和700～500 hPa相对湿度(R_HUM)有关；Ⅱ区TC强度与700～500 hPa R_HUM、500 hPa O_MEGA和风垂直切变(V_WS)有关，Ⅱ区TC频次与500 hPa O_MEGA和V_WS有关。秋季Ⅰ区TC频次与500 hPa O_MEGA有关。无论夏季与秋季，TC活动与海洋因子均表现为不显著的相关或显著的负相关关系，不同区域影响TC活动的局地环境因子有所不同，与季节和区域划分有关，具有复杂性。（3）强季风槽可通过低层大的R_vor、中层上升运动及高湿影响夏、秋季I区TC活动；Nino3.4区海温变暖可使夏季Ⅱ区850 hPa出现异常偏西风，导致低层R_vor增大；200 hPa出现异常反气旋环流，导致V_ws减弱；低层大的R_vor配合高层反气旋环流使中层上升运动和水汽辐合增加，进而影响该区TC活动。当WNP副高西伸（东缩）加强（减弱）时，会引起局地负（正）涡度异常从而导致移入夏季Ⅲ区的TC频次减少（增多）,当中层引导气流加强时会导致更多的强TC移入该区；两个高压之间的相对低压区辐合有利于低层R_vor增大，进而影响秋季Ⅲ区TC活动。更多还原

【Abstract】 This study utilises best-track datasets of tropical cyclones(TCs) from the Joint Typhoon Warning Center(JTWC), Japan Meteorological Agency Tokyo Regional Specialised Meteorological Center(RSMC), and Shanghai Typhoon Institute of China Meteorological Administration(CMA), along with NCEP reanalysis data and correlation analysis methods, to investigate the fundamental characteristics of TC intensity and frequency in different seasons(July-September for summer and October-November for autumn) and subregions over the Western North Pacific(WNP) during 1989-2020, as well as their relationships with local environmental factors. The results indicate that:(1) The total TC frequency observed in the three summer WNP subregions(Area I: 10°-25°N, 110°-145°E; Area II: 10°-25°N, 145°E-180°; Area III: 25°-37.5°N, 125°E-180°) is 10164, while the total TC frequency in the three autumn subregions(Area I: 5°-17.5°N, 110°E-180°; Area II: 17.5°-35°N, 142.5°E-180°; Area III: 17.5°-35°N, 120°-142.5°E) is 4984. This demonstrates significantly higher TC activity in summer than in autumn.(2) TC activity during both summer and autumn exhibits statistically significant correlations with 850 hPa relative vorticity(RVOR), except for Area II in autumn. In addition to low-level RVOR, summer TC frequency in Area I is associated with 500 hPa vertical velocity(OMEGA) and 700-500 hPa relative humidity(RHUM). Summer TC intensity in Area II is linked to 700-500 hPa RHUM, 500 hPa OMEGA, and vertical wind shear(VWS), while summer TC frequency in Area II correlates with 500 hPa OMEGA and VWS. Autumn TC frequency in Area I shows a relationship with 500 hPa OMEGA. Regardless of season, TC activity generally displays either nonsignificant correlations or significantly negative correlations with oceanic factors. The local environmental factors influencing TC activity vary across regions and seasons, depending on seasonal and regional divisions, which indicates complex interactions.(3) A strong monsoon trough enhances TC activity in summer and autumn Area I through low-level high RVOR, mid-level ascending motion, and high humidity. The warming of sea surface temperature in the Nino3.4 region can induce anomalous westerly winds at 850 hPa in Area II during summer, leading to increased low-level RVOR. Concurrently, an anomalous anticyclonic circulation emerges at 200 hPa, resulting in reduced VWS. The combination of the enhanced low-level RVOR and upper-level anticyclonic circulation further strengthens mid-level upward motion and moisture convergence, thereby influencing TC activity in this region. When the Western Pacific subtropical high extends westward(retreats eastward), it generates localised negative(positive) vorticity anomalies, leading to reduced(increased) TC frequency entering summer Area III. Strengthened mid-level steering flows further enhance the intrusion of intense TCs into this region. The convergence in the relative low region between two highs enhances low-level RVOR, which consequently modulates TC activity in Area III during autumn.更多还原