Rainfall asymmetries of landfalling tropical cyclones along the South China coast

Abstract

The rainfall distribution associated with landfalling tropical cyclones (TCs) along the South China coast are examined using radar data from Hong Kong Observatory (HKO). This preliminary study relates the landfall direction, and possible rotations/transitions of TC rainfall asymmetries before and after the landfall. Three types of landfalling TCs on the South China coast are categorized: from the east, normal to the coast and from the southwest. For those from the east, the rainfall maximum rotates anticyclonically from the southwest before later landfall to the northwest. TCs making landfall perpendicular to the coast have a rainfall maximum remaining in the southwest quadrant throughout the landfall process. For TCs making landfall from the southwest, the rainfall maximum rotates cyclonically from the southeast before later landfall to the northeast. The relative importance of the impact of land properties and vertical wind shear on these rainfall asymmetries is investigated by using a numerical model. Sensitivity tests show that the rotations/transitions of landfalling TC rainfall asymmetry appear to be insensitive to land properties (e.g. moisture availability, surface friction and topography), but result primarily from changes in the orientations of the vertical wind shear in the environment. However, the surface friction of the landmass appears to contribute to the enhancement of rainfall intensity.

The Response and Feedback of Ocean Mesoscale Eddies to Four Sequential Typhoons in 2014 Based on Multiple Satellite Observations and Argo Floats

“…Figure 2i-l show the rainfall distribution during the passage of sequential typhoons, and the maximum rainfall exceeded 200 mm/day. Figure 2i-j show that the rainfall induced by typhoon Neoguri and Matmo was stronger on the left-hand side of the track than on the righthand side, which coincides with the findings of previous studies [46][47][48][49]. However, the subsequent typhoons, Nakri and Halong, induced a right-bias rainfall (Figure 2k-l), which was probably due to the asymmetrical precipitable water vapor distribution caused by the first two typhoons.…”

Landfalling tropical cyclone characteristics and their multi‐timescale variability connected to monsoon and easterly formation environments over the western North Pacific

“…Previous studies confirmed that TC landfall impacts (e.g. rainfall and wind) are affected by TC characteristics including track direction (Lee et al ., 2006; Chan et al ., 2019), intensity (Emanuel, 2005; Yu et al ., 2017), size (Matyas, 2006; Chen et al ., 2011), translation speed (Su et al ., 2012; Hsu et al ., 2013), duration (Done et al ., 2018), asymmetric structure (Lonfat et al ., 2004; Chen et al ., 2016), as well as interactions among these characteristics (Teng et al ., 2020a). Landfall impacts are also affected by the interaction of TCs with the land surface, causing phase‐locked wind and rainfall patterns (Chang et al ., 1993; Lin et al ., 2001; Chiao and Lin, 2003; Hsu et al ., 2013; Lu et al ., 2018).…”

Observed Shear-Relative Rainfall Asymmetries Associated with Landfalling Tropical Cyclones

“…Asymmetries in the TC rainfall associated with landfalling can be modulated by not only VWS [30][31][32][33][34], but also some other factors, such as nonuniform surface features including land-sea contrast and local topographic effect [31,32,[34][35][36][37][38][39] and interaction between TCs and synoptic weather systems [38,40,41]. In general, the landfalling TCs regularly had an asymmetry with a downshear to downshear-left rainfall maximum near the coastal regions, which is consistent with the studies for TCs over the ocean [3,19,42].…”