Changing relationship between La Niña and tropical cyclone landfalling activity in South China (La Niña and TC landfalling activity in South China)

Abstract

This study investigates the effect of El Niño–Southern Oscillation and Indo‐Pacific warm pool sea‐surface temperature (SST) on tropical cyclone (TC) landfalling activity along the South China coast and develops a scheme for predicting this activity. In general, landfalling activity tends to be suppressed in El Niño years but a large uncertainty is found for La Niña years. Landfalling activity is generally enhanced in La Niña years before 1997 but suppressed in those after 1997, which may be related to the changes in TC frequency and track pattern over the western North Pacific (WNP) as well as the northward shift in genesis locations. The Indo‐Pacific warm pool SST is found to be related to the TC activity over the WNP and an SST index, defined as the average SST anomalies over the North Indian Ocean and the sea near the Philippines, is used to represent this anomaly. A significant warming of the Indo‐Pacific warm pool is found in the recent decade. The temperature change of this warm pool appears to modulate the TC activity over the WNP and TC landfalling activity in South China in a La Niña year, with an enhancement (a suppression) of TC activity if a cooling (warming) is found. This difference is related to the changes in the strength of monsoon trough, vertical wind shear and steering flow pattern. Based on these results, a schematic prediction scheme of landfalling activity in South China is proposed. Landfalling activity is likely to be normal or below normal if an El Niño event is expected to develop during the TC season. If a La Niña event is expected, and the predicted state of the Indo‐Pacific warm pool (obtained using the persistence forecast) shows a warming (cooling), landfalling activity is likely to be normal or below normal (above normal).

Variability of Tropical Cyclone Landfalls in China

“…TC tracks in the WNP can be classified into different types by predefining regions under threat (Liu and Chan 2008;Wang et al 2013;Colbert et al 2015;Shan and Yu 2020b). Three prevailing types are considered in this study.…”

“…It is known that most of the TCs that occur in the WNP ocean basin can be classified into a few different types according to the geometry of their tracks (Camargo et al 2007;Liu and Chan 2008;Chu et al 2010;Colbert et al 2015). Those making landfall in southern China are essentially moving straight westward whereas those making landfall in southeastern China are generally moving northwestward when approaching the coast.…”

Typhoon storm surge in the southeast Chinese mainland modulated by ENSO

“…6 , which shows that the majority of the annual-maximum typhoons move northwestward. Liu and Chan 33 , 34 showed that, landfalling typhoons in the South China (Guangdong and Hainan provinces) tend to be normal or below normal during El Niño years. Therefore, there are more strong typhoons making landfalls in Guangdong, Guangxi, and Hainan in non-El Niño years, which can enhance local AMTSSs therein.…”

Combined Effect of the PDO and ENSO on the Date of the First Tropical Cyclone Landfall in Continental East Asia

“…It has been verified in numerous previous studies that the El Niño‐Southern Oscillation (ENSO) is a crucial factor influencing the frequency of TC genesis in the northwestern and southeastern WNP. Specifically, it is believed that TC track and landfall are closely related with the ENSO (Choi, Ha, & Jin, 2019; Kim et al., 2011; K. S. Liu & Chan, 2003, 2018; B. Wang & Chan, 2002; Zhan et al., 2018; H. Zhang & Guan, 2014; W. Zhang et al., 2012; Zhou & Lu, 2019). K. S. Liu and Chan (2003) pointed out that a strong El Niño event can reduce the frequency of TC landfall, whereas more TCs make landfall in the South China coast during La Niña years.…”