Recent Decrease in the Difference in Tropical Cyclone Occurrence between the Atlantic and the Western North Pacific

Abstract

Climatologically, among all ocean basins, the western North Pacific (WNP) has the largest annual number of tropical cyclones (TCs) of around 26 while the Atlantic has around 13, yielding a difference of 13. However, the difference is −7 in 2020, with 30 TCs in the Atlantic and 23 in the WNP, which is the most negative difference within the last 46 years. In fact, during the last 26 years, the difference in TC number is below 10 in ten years, with four years being negative. Such a decreasing difference in TC number can be attributed to the natural multidecadal variation of the Atlantic Multidecadal Oscillation and Interdecadal Pacific Oscillation, as well as other external forcings such as anthropogenic aerosol forcing and increased greenhouse gases, with the additional impact from the La Niña condition. This result has significant implications on climate model projections of future TC activity in the two ocean basins.

摘 要

从气候学角度来看,在所有海洋盆地中,西北太平洋的热带气旋年发生数量最多,每年约为26个,而大西洋约为13个,两者平均差异为13个。然而,2020年西北太平洋出现了23个热带气旋,大西洋却有30个,差异为 -7个,这是过去46年来的最大负偏差。事实上,在过去的26年中,有10年热带气旋的数量差异低于10,其中4年为负数。这种热带气旋数量差异的减少,可归因于大西洋多年代际振荡和太平洋年代际振荡的自然多年代际变化,以及其他外部强迫,如人为气溶胶强迫和温室气体增加,以及拉尼娜现象的额外影响。这一结果对两个海洋盆地未来热带气旋活动的气候模型预测具有重要意义。