Variability of tropical cyclone (TC) genesis frequency in the western North Pacific and South Pacific ocean basins in the interdecadal scale is studied. It is demonstrated that the TC genesis frequency in these ocean basins experienced an abrupt decrease near the end of the 20th century. The decreased occurrence of TC genesis in the recent two decades is mainly located in the low-latitude regions at the eastern side of the two ocean basins. It is also shown that a significant part of the decreased TC genesis occurred during October to December, i.e., the post-peak season in the western North Pacific ocean basin and the pre-peak season in the South Pacific ocean basin. The interdecadal trend of variation of the TC genesis frequency in these adjacent two ocean basins seems to be mainly due to a common mechanism, i.e., the variation of the atmospheric vorticity. In contrary to the decrease of the total TC genesis, the intense typhoon occurrence frequency experienced an interdecadal increase during the same period. This trend for intense typhoon is particularly clear in the western North Pacific ocean basin. The zonal distribution of the increased number of the intense typhoon occurrence shows a similar pattern with the increased value of sea surface temperature. It is then suggested that the variation of the intense typhoon occurrence frequency in the western North Pacific ocean basin is related to a change of the La Nina-like sea surface warming pattern.

中文翻译：

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西北太平洋和南太平洋海盆热带气旋发生频率的年代际变化

研究了北太平洋西部和南太平洋海盆在年代际尺度上热带气旋（TC）发生频率的变化。研究表明，这些洋盆中的台风发生频率在 20 世纪末出现了急剧下降。近二十年来台风成因减少主要分布在两大洋盆东侧的低纬度地区。还表明，TC 成因减少的很大一部分发生在 10 月至 12 月，即北太平洋西部海盆的后旺季和南太平洋海盆的前旺季。这两个相邻海盆中 TC 发生频率的年代际变化趋势似乎主要是由于一个共同的机制，即 大气涡度的变化。与台风总成因减少相反，强台风发生频率在同一时期经历了年代际增加。这种强台风趋势在西北太平洋海盆中尤为明显。强台风发生次数增加的带状分布与海面温度值的增加相似。进而提出西北太平洋海盆强台风发生频率的变化与类拉尼娜海面增温模式的变化有关。这种强台风趋势在西北太平洋海盆中尤为明显。强台风发生次数增加的带状分布与海面温度值的增加相似。进而提出西北太平洋海盆强台风发生频率的变化与类拉尼娜海面增温模式的变化有关。这种强台风趋势在西北太平洋海盆中尤为明显。强台风发生次数增加的带状分布与海面温度值的增加相似。进而提出西北太平洋海盆强台风发生频率的变化与类拉尼娜海面增温模式的变化有关。