Abstract The present study discovered a strong negative correlation between Korea-landfalling tropical cyclone (TC) frequency and Pacific Decadal Oscillation (PDO) in the summer. Thus, the present study selected years that had the highest PDO index (positive PDO years) and years that had the lowest PDO index (negative PDO years) to analyze a mean difference between the two phases in order to determine the reason for the strong negative correlation between the two variables. In the positive PDO years, TCs were mainly generated in the southeastern part of the western North Pacific, and lower TC passage frequency was found in most regions in the mid-latitude in East Asia. Moreover, a slightly weaker TC intensity than that in the negative PDO years was revealed. In order to determine the cause of the TC activity revealed in the positive PDO years, 850 hPa and 500 hPa stream flows were analyzed first. In the mid-latitude region in East Asia, anomalous huge cyclonic circulations were strengthened, while anomalous anticyclonic circulations were strengthened in the low-latitude region. Accordingly, Korea was being influenced by anomalous northwesterlies, which played a role in blocking TCs from moving northward to Korea. The results of analysis on 850 hPa air temperature, precipitation, 600 hPa relative humidity, and sea surface temperature (SST) showed that negative anomalies were strengthened in the northwest region in the western North Pacific while positive anomalies were strengthened in the southeast region. The atmospheric and oceanic environments were related to frequent occurrences of TCs in the southeast region in the western North Pacific during the positive PDO years. All factors of air temperature, precipitation, 600 hPa relative humidity, and SST revealed negative (positive for vertical wind shear) anomalies near Korea, so that atmospheric and oceanic environments were formed that could rapidly weaken TC intensity, even if the TCs moved northward to Korea in the positive PDO years.

中文翻译：

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韩国登陆热带气旋活动与太平洋年代际涛动的负相关

摘要 本研究发现夏季登陆韩国的热带气旋（TC）频率与太平洋年代际涛动（PDO）呈强烈负相关。因此，本研究选择了 PDO 指数最高的年份（正 PDO 年）和 PDO 指数最低的年份（负 PDO 年）来分析两个阶段之间的平均差异，以确定强负值的原因两个变量之间的相关性。在正 PDO 年份，TC 主要产生于西北太平洋东南部，东亚中纬度大部分地区 TC 通过频率较低。此外，显示出比负 PDO 年略弱的 TC 强度。为了确定正 PDO 年中揭示的 TC 活动的原因，首先分析了 850 hPa 和 500 hPa 的气流。东亚中纬度地区异常巨大气旋环流加强，而低纬度地区异常反气旋环流加强。因此，韩国受到异常西北风的影响，这在阻止 TC 向北移动到韩国方面发挥了作用。850 hPa气温、降水、600 hPa相对湿度和海表温度（SST）分析结果表明，西北太平洋地区负距平增强，东南地区正距平增强。大气和海洋环境与正 PDO 年期间西北太平洋东南地区 TC 的频繁发生有关。