Possible relation of the western North Pacific monsoon to the tropical cyclone activity over western North Pacific

Choi, Jae‐Kap; Kim, Baek-Jo; Zhang, Renhe; Park, Ki-Jun; Kim, Jeoung-Yun; Cha, Youngsu; Nam, Jae-Cheol

doi:10.1002/joc.4558

Cited by 19 publications

(31 citation statements)

References 39 publications

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“…The WNP summer monsoon (WNPSM) is considered to be one of the most important large-scale systems for breeding boreal summer (June-August) WNP TC genesis. Previous studies have suggested that about 70% of the total number of WNP TCs are associated with the WNP monsoon trough (WNPMT) (Gray 1968;Frank 1987;McBride 1995;Ritchie and Holland 1999;Harr and Chan 2005;Chen et al 2006;Wu et al 2012;Molinari and Vollaro 2013;Zong and Wu 2015a,b;Choi et al 2016;Wang and Wu 2018). The importance of the WNPMT on TC genesis has been largely explained by two reasons.…”

Section: Introductionmentioning

confidence: 99%

Recent Strengthening of the Relationship between the Western North Pacific Monsoon and Western North Pacific Tropical Cyclone Activity during the Boreal Summer

2019

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This study examines the association between the western North Pacific (WNP) summer monsoon (WNPSM) and WNP tropical cyclone (TC) frequency during June–August from 1979 to 2016. The interannual relationship between the WNPSM and the total number of WNP TCs has strengthened since 1998. There has also been a significant reduction in the number of TCs forming within the WNP monsoon trough (WNPMT)—hereafter called ITCs, for internal or inside TCs—since 1998. These two important features are found to be closely associated with the climate regime shift that occurred around 1998. During 1998–2016, the Pacific decadal oscillation (PDO) tended to be in a cold phase, with an increasing occurrence of central Pacific–type El Niño–Southern Oscillation (ENSO) events, whereas the 1979–97 period tended to be characterized by a warm phase of the PDO and east Pacific–type ENSO events. During 1998–2016, the tropical Pacific was characterized by enhanced easterlies, which led to a westward-retreated WNPMT that caused a significant decrease in ITCs over the WNP basin. However, there was little change in TCs outside of the WNPMT region (hereafter called OTCs) compared to that before 1998. A significant in-phase (out-of-phase) relationship between the WNPSM and the number of ITCs (OTCs) is observed before 1998, thus greatly weakening the WNPSM–TC relationship. The recent enhanced relationship between the WNPSM and TCs is mainly due to a strong in-phase relationship between the WNPSM and ITCs. The interannual change in ITCs is mainly controlled by WNPSM changes since 1998, while OTC changes are mainly modulated by changes in the tropical upper-tropospheric trough.

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Section: Introductionmentioning

confidence: 99%

Recent Strengthening of the Relationship between the Western North Pacific Monsoon and Western North Pacific Tropical Cyclone Activity during the Boreal Summer

2019

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“…The WNP subtropical high and WNP summer monsoon could have profound effects on WNP TC activities [24,[37][38][39][40][41]. The observed changes of low-level atmospheric circulations (Figures 4 and 5) may be closely related to the changes of WNP subtropical highs and monsoons.…”

Section: Changing Tendencies In Wnp Subtropical High and Monsoonmentioning

confidence: 90%

A Contrast of Recent Changing Tendencies in Genesis Productivity of Tropical Cloud Clusters over the Western North Pacific in May and October

Peng

Wang

et al. 2021

Atmosphere

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Tropical cloud clusters (TCCs) are embryos of tropical cyclones (TCs) and may have the potential to develop into TCs. The genesis productivity (GP) of TCCs is used to quantify the proportion of TCCs that can evolve into TCs. Recent studies have revealed a decrease in GP of western North Pacific (WNP) TCCs during the extended boreal summer (July–October) since 1998. Here, we show that the changing tendencies in GP of WNP TCCs have obvious seasonality. Although most months could see recent decreases in GP of WNP TCCs, with October experiencing the strongest decreasing trend, May is the only month with a significant recent increasing trend. The opposite changing tendencies in May and October could be attributed to different changes in low-level atmospheric circulation anomalies triggered by different sea surface temperature (SST) configurations across the tropical oceans. In May, stronger SST warming in the tropical western Pacific could prompt increased anomalous westerlies associated with anomalous cyclonic circulation, accompanied by the weakening of the WNP subtropical high and the strengthening of the WNP monsoon. Such changes in background atmospheric circulations could favor the enhancement of atmospheric eddy kinetic energy and barotropic energy conversions, resulting in a recent intensified GP of WNP TCCs in May. In October, stronger SST warming in the tropical Atlantic and Indian Oceans contributed to anomalous easterlies over the tropical WNP associated with anomalous anticyclonic circulation, giving rise to the suppressed atmospheric eddy kinetic energy and recent weakened GP of WNP TCCs. These results highlight the seasonality in recent changing tendencies in the GP of WNP TCCs and associated large-scale atmospheric-oceanic conditions.

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“…The above result suggests that the anomalous anticyclone strengthened in the mid-latitude region of East Asia during high TCGF years implies weakening of the EASM, and the anomalous cyclone strengthened in the WNP implies the strengthening of the WNPSM. Regarding this, Choi et al (2016) have found that when the WNPSM is strengthened, the TCGF increases, but the EASM tends to be weakened.…”

Section: Easm and Wnpsmmentioning

confidence: 95%

Possible Relationship between Korean Heat Wave and Western North Pacific Tropical Cyclone Genesis Frequency

Cha

Choi

Ahn

2021

Preprint

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This study conducted a correlation analysis between tropical cyclone genesis frequency (TCGF) in the western North Pacific (WNP) and heat wave days (HWD) in Korea during July and August for 46 years (1973–2018) and we found a strong positive correlation between them. This implied that the higher the TCGF in the WNP during July and August, the higher the HWD in Korea becomes. To examine the cause of the statistically significant positive correlation between the TCGF during July and August in the WNP and the HWD in Korea, 15 years with the highest frequency and the lowest frequency out of the 46 years in the TCGF time series were selected and defined as high TCGF years and low TCGF years, respectively. An analysis of the difference in 2m air temperature (Air2m) between the two groups showed that in the mid-latitude region of Asia, the Air2m was higher during the high TCGF years. Thus, it could be seen from this analysis that the increase of HWD during the high TCGF years is likely to occur in the entire mid-latitude region of East Asia as well as in Korea. According to the difference in atmospheric circulations between the two groups, in all layers of the troposphere, anomalous anticyclonic and cyclonic circulations were strengthened in the mid-latitude region of East Asia and in the WNP, respectively, which was similar to the Pacific-Japan (PJ) teleconnection pattern. Furthermore, the anomalous anticyclone strengthened in the mid-latitude region of East Asia was associated with the weakening of the East Asian summer monsoon, and the anomalous cyclone strengthened in the WNP was associated with the WNP summer monsoon. The difference in the vertical meridional circulation averaged over the longitude range where Korea is located showed that anomalous upward and downward flows were strengthened in the WNP and in the latitude where Korea is located, respectively. This implied that the local Hadley circulation was strengthened during the high TCGF years. An analysis of the difference in the mean sea surface temperature during July and August showed that the eastern Pacific (EP) La Niña was strengthened during the high TCGF years. To determine the cause of the formations of anomalous anticyclones in the mid-latitude region of East Asia and in the WNP during the high TCGF years, the 500 hPa wave activity flux was analyzed. The wave activity flux originated from the North Atlantic, passed through the Scandinavian Peninsula, the North coast of Russia, and East Siberia before reaching Korea and the WNP. This spatial distribution was similar to the Scandinavia teleconnection pattern. Therefore, we conclude that the anomalous anticyclone formed in the mid-latitude region of East Asia and the anomalous cyclone formed in the WNP during the high TCGF years are associated with the Scandinavia teleconnection pattern.

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Possible relation of the western North Pacific monsoon to the tropical cyclone activity over western North Pacific

Cited by 19 publications

References 39 publications

Recent Strengthening of the Relationship between the Western North Pacific Monsoon and Western North Pacific Tropical Cyclone Activity during the Boreal Summer

Recent Strengthening of the Relationship between the Western North Pacific Monsoon and Western North Pacific Tropical Cyclone Activity during the Boreal Summer

A Contrast of Recent Changing Tendencies in Genesis Productivity of Tropical Cloud Clusters over the Western North Pacific in May and October

Possible Relationship between Korean Heat Wave and Western North Pacific Tropical Cyclone Genesis Frequency

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