Relationships between the Southwest Monsoon Surge and the Heavy Rainfall Associated with Landfalling Super Typhoon Rammasun

Abstract

Based on the China Meteorological Administration (CMA) best-track data, the ERA5 reanalysis, and the Global Precipitation Measurement (GPM) precipitation data, this paper analyzes the reasons for the heavy rainfall event of Super Typhoon Rammasun in 2014, and the results are as follows: (1) Rammasun was blocked by the western Pacific subtropical high (WPSH), the continental high, and the mid-latitude westerly trough. Such a stable circulation pattern maintained the vortex circulation of Rammasun. (2) During the period of landfall, the southwest summer monsoon surge was reinforced due to the dramatic increase of the zonal wind and the cross-equatorial flow near 108° E. The results of the dynamic monsoon surge index (DMSI) and boundary water vapor budget (BWVB) show that the monsoon surge kept providing abundant water vapor for Rammasun, which led to the enhanced rainfall. (3) The East Asian monsoon manifested an obvious low-frequency oscillation with a main period of 20–40 days in the summer of 2014, which propagated northward significantly. When the low-frequency oscillation reached the extremely active phase, the monsoon surge hit the maximum and influenced the circulation of Rammasun. Meanwhile, the convergence and water vapor flux associated with the low-frequency oscillation significantly contributed to the heavy rainfall.

The influence of different intensity of monsoon on typhoon precipitation: a comparative study of typhoons Soudelor and Maria

“…Previously, the monsoon surge was often defined as the regional average of the 850-hPa zonal wind over the designated area (Dong et al, 2010). However, considering the east-west movement of typhoons in the Northwest Pacific, the dynamic monsoon surge index (DMSI) (Zhao et al, 2021;Liu et al, 2022b) is used to distinguish between the typhoon circulation and monsoon surge circulation before and after typhoon landfall, which is defined as:…”

“…The results show that they are positively correlated and associated with precipitation enhancement. Additional studies have shown that due to the low-frequency oscillation of the East Asian summer monsoon, the monsoon surge features a northward propagation, which continues to provide water vapor for typhoons, thus affecting the heavy rainfall in typhoons (Liu et al, 2022a). Therefore, how monsoon flow affects typhoon activity, especially regarding its impact on heavy precipitation, needs further study.…”

Impact of Thermal Forcing over the Southeast of the Tibetan Plateau on Frequency of Tropical Cyclones Affecting Guangxi during Boreal Summer

“…In particular, the frequency of landfalling typhoons in southern China has increased since the year 2000 [8][9][10]. Tropical cyclones such as Haiyan (in 2013), Rammasun (in 2014), and Mangkhut (in 2018) have caused tremendous damages in southern China [11][12][13]. In addition to the intensity and track of tropical cyclones, the spatial distribution of the population is also an important factor in exposing people to the hazardous tropical cyclones events.…”