With the tropical cyclone (TC) size parameter defined as the radius of 17‐m·s⁻¹ oceanic surface wind, 225 TC cases were recorded in the western North Pacific during 2000–2009 based on the QuikSCAT near‐surface wind vector database and the best‐track dataset. In accordance with the symmetry index (the ratio of minimum and maximum quadrant sizes), the TCs were classified into symmetric and asymmetric structures. The asymmetric TCs were divided into four types: the northeast, southeast, southwest, and northwest. The spatio‐temporal characteristics of these TC types were further investigated. The monthly variation and the spatial distribution of maximum quadrant TC size exhibited significant differences among the four types. By contrast, the quadrant size of the symmetric TCs from June to November showed few changes (2.6°–2.7° latitude). It was found that the TC lifetime is an important factor affecting the quadrant TC size because of its close relationship with the activities of the western Pacific subtropical high. In addition, the climatological mean circulation also has a notable influence on the quadrant TC size through superposition of prominent background wind. Symmetric TCs are more likely to occur in the oceanic region where the background low‐level wind is the weakest.

中文翻译：

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北太平洋西部象限热带气旋大小的月变化和空间分布

使用热带气旋（TC）大小参数定义为半径17-m·s ^-1根据QuikSCAT近地表风矢量数据库和最佳航迹数据集，在2000-2009年期间，北太平洋西部记录了225 TC例海洋表面风。根据对称指数（最小和最大象限大小之比），将TC分为对称和不对称结构。不对称TC分为四种类型：东北，东南，西南和西北。这些TC类型的时空特征得到了进一步研究。四种象限之间最大象限的月变化和空间分布表现出显着差异。相比之下，从6月到11月，对称TC的象限大小几乎没有变化（纬度2.6°至2.7°）。已经发现，TC寿命是影响象限TC大小的重要因素，因为它与西太平洋副热带高压的活动密切相关。此外，气候平均环流还通过叠加显着的背景风对象限TC大小产生显着影响。对称TC更有可能发生在背景低空风最弱的海洋区域。