Weak Tropical Cyclones Dominate the Poleward Migration of the Annual Mean Location of Lifetime Maximum Intensity of Northwest Pacific Tropical Cyclones since 1980

Abstract

The poleward migration of the annual mean location of tropical cyclone (TC) lifetime maximum intensity (LMI) has been identified in the major TC basins of the globe over the past 30 years, which is particularly robust over the western North Pacific (WNP). This study has revealed that this poleward migration consists mainly of weak TCs (with maximum sustained surface wind speed less than 33 m s−1) over the WNP. Results show that the location of LMI of weak TCs has migrated about 1° latitude poleward per decade since 1980, while such a trend is considerably smaller for intense TCs. This is found to be linked to a significant decreasing trend of TC genesis in the southern WNP and a significant increasing trend in the northwestern WNP over the past 30 years. It is shown that the greater sea surface temperature (SST) warming at higher latitudes associated with global warming and its associated changes in the large-scale circulation favor more TCs to form in the northern WNP and fewer but stronger TCs to form in the southern WNP.

What Has Controlled the Poleward Migration of Annual Averaged Location of Tropical Cyclone Lifetime Maximum Intensity Over the Western North Pacific Since 1961?

“…The poleward migration rate of φ LMI increases markedly to 0.51° latitude decade −1 from 1980 to 2016, which is significant at the 0.01 level based on an F test. This rate is similar to what was found in Zhan and Wang ().…”

“…There exists a poleward φ LMI trend of 0.24° latitude decade −1 (statistically significant at the 0.05 level based on an F test), indicating a notable northward shift of TC LMI location since 1961. Note that this rate is much smaller than that documented in previous publications (Daloz & Camargo, ; Kossin et al, ; Moon et al, ; Zhan & Wang, ), which only analyzed φ LMI trends since the early 1980s. This raw trend is comparable to the 1945–2013 φ LMI tendency of 0.21° latitude decade −1 after removing the influences of El Niño–Southern Oscillation (ENSO) and PDO found by Kossin et al ().…”

“…In this study, long‐term tendencies of WNP TC φ LMI and its components ( φ G , Δ φ , V φ , and Δ t ) are examined from 1961 to 2016. Although there is a notable poleward shift of annual mean φ LMI since 1961, the poleward migration rate is much smaller than those studies examining trends since ~1980 (Daloz & Camargo, ; Kossin et al, ; Moon et al, ; Zhan & Wang, ). These differences in results occur due to there being little trend in φ LMI prior to 1980.…”

“…Daloz and Camargo () showed that due to a northward migration of favorable environmental conditions, TC genesis moved toward higher latitudes from 1980 to 2013, which further resulted in the northward shift of φ LMI . In addition, Zhan and Wang () demonstrated that the φ LMI variation of weak TCs (with LMI lower than 33 m s −1 ) was the dominant factor contributing to the poleward φ LMI shift of WNP TCs since 1980.…”

“…Daloz and Camargo (2017) showed that due to a northward migration of favorable environmental conditions, TC genesis moved toward higher latitudes from 1980 to 2013, which further resulted in the northward shift of φ LMI . In addition, Zhan and Wang (2017) Most φ LMI -related publications have focused on the period since the early 1980s. This time span, which is only around 30 years in length, may be too short to distinguish long-term trends from interdecadal variations (Chan, 2006).…”