摘要:基于多平台热带气旋表面风场资料（MTCSWA），研究了2007～2016年6～11月西北太平洋上不同尺度热带气旋（TC）的气候统计特征，TC各级风圈半径在不同象限的变化特征、风场结构的对称度及二者与强度变化之间的相关性。利用7级风圈半径与TC近中心最大持续风速（MSW）来定义TC的尺度和强度。结果表明，西北太平洋上TC的平均尺度为221.9 km，其中小TC平均尺度为96.4 km，大TC平均尺度为346.4 km。大TC活动位置的空间分布较小TC更为集中，整体活动范围较小TC偏北。TC尺度的峰值出现在8月和10月。在TC的风场结构中，7级、10级、12级风圈的平均半径分别为221.9、121.0、77.4 km。TC风圈的对称度的统计结果表明7级风圈的对称度最低，12级风圈的对称度最高。相关分析表明，在TC的生命史中，各级风圈半径与其强度存在一定的正相关关系，其中12级风圈半径与强度的相关性最低；对于同一风圈而言，在TC的不同发展阶段中，不同象限的风圈半径与强度的相关性不同。在TC的风场结构中，风圈的对称度与TC强度的相关性随着风圈强度的增强而减弱，只有7级风圈的对称度在TC的整个生命周期中表现出与TC强度之间的弱的正相关关系。
关键词:MTCSWA资料/
风场插值/
相关性分析/
对称度
Abstract:On the basis of the MTCSWA (Multiplatform Tropical Cyclone Surface Winds Analysis) data, the climatic statistical characteristics of tropical cyclones (TCs) at different sizes, the variation of the averaged radial extent of different significant wind speed thresholds (i.e., 34, 50, and 65 kt, 1 kt≈0.514 m/s) in different quadrants, and the axisymmetricity of the radial extent of different wind speed thresholds and their correlation with TC intensity over the western North Pacific from 2007 to 2016 are investigated. In this study, the size and intensity of TCs are defined as the azimuthally averaged radius at which wind speed decreases to 34 kt (≈17.5 m/s) from the center and the maximum sustained winds near the TC center, respectively. The mean size of TCs over the western North Pacific Ocean is 221.9 km, with small TCs of 96.4 km and large TCs of 346.4 km. The activity location of large TCs is more concentrated, with a more northward distribution, than that of small TCs. The peak value of the mean size of all TCs occurs in August and October. The mean values of the azimuthally averaged radial extents of the 34, 50, and 65 kt wind speed thresholds are 221.9, 121.0, and 77.4 km, respectively. According to the definition of axisymmetricity, the radial extent of the 34 kt wind speed threshold has the lowest axisymmetricity and the 65 kt wind speed threshold has the highest axisymmetricity. Positive correlations exist between the radial extents of the 34, 50, and 65 kt wind speed thresholds and the TC intensity during the TC’s lifetime, among which the correlation between the radial extent of the 65 kt wind speed threshold and the TC intensity is the lowest. For a certain wind speed threshold, the correlation between its radial extent and TC intensity varies in different quadrants at different stages of the TC’s lifetime. The higher the wind speed is, the weaker the correlation between the axisymmetricity of its radial extent and TC intensity. Only the axisymmetricity of the radial extent of the 34 kt wind speed threshold shows a weak positive correlation with TC intensity during the TC’s lifetime.
Key words:MTCSWA data/
Wind field interpolation/
Correlation analysis/
Axisymmetricity
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