Modelling the effects of land–sea contrast on tropical cyclone precipitation under environmental vertical wind shear

Abstract

The precipitation pattern of a landfalling tropical cyclone (TC) with and without a weak environmental vertical wind shear (VWS) is investigated using WRF/NCAR model simulations under idealized conditions. In the simulations without VWS, results show that for the outer band (r ∼ 100–300 km), the cold and dry air originating over smooth land is advected offshore, reduces the stability and develops a band of rainfall on the eastern side of the TC, while the rough land surface tends to trigger more rainfall to the west. For the inner core (r< 100 km), there is only small rainfall asymmetry when the land surface is smooth and dry, but with a rough land surface, the rainfall asymmetry becomes evident and generally stronger rainfall is found over the land areas to the west. Further experiments are performed to compare the effects from weak environmental VWS and land–sea contrast. It is found that the storm‐scale (within 400 km from TC centre) VWS changes continuously in direction and magnitude due to asymmetric diabatic heating and accompanying upper‐level winds. The rainfall pattern in the inner‐core region follows closely the storm‐scale VWS with a downshear‐left relationship regardless of the surface properties, while in the outer‐band region, rainfall distribution is first strongly affected by the surface roughness before landfall and by the environmental VWS afterwards. Therefore, an evolving rainfall–VWS (both environmental and due to storm‐scale dynamics) relationship during TC landfall results.

Impact of Tropical Cyclone Landfall Angle on Storm Surge Along the Mid‐Atlantic Bight

“…The parameterization schemes used include the following: WRF single‐moment 6‐class microphysics scheme (Hong & Lim, ), Yonsei University boundary layer scheme (Hong et al, ), Tiedtke cumulus parameterization (Tiedtke, ), Rapid Radiative Transfer Model for General Circulation Models for shortwave and longwave radiation parameterization (Iacono et al, ), and the Noah land surface model (Chen & Dudhia, ). The SST remained time invariant and spatially uniform at 28 °C (Bruyère et al, ; Kimball, ; Li et al, ). As reported by Bruyère et al (), a constant SST does not negatively impact the development of cyclones, and on the contrary, its effect is that of sustaining a stronger TC throughout the simulation.…”

Rainfall asymmetries of landfalling tropical cyclones along the South China coast

“…Corbosiero and Molinari, ; Chen et al ., ; Cecil, ; Ueno, ) and land properties (e.g. Li et al ., , , ), such as moisture availability, surface friction and topography, may contribute to the different distributions of convection for TCs making landfall from different directions. The results of such an investigation are presented in the next section.…”

“…In addition, the impacts of land properties on landfalling TC rainfall asymmetries on the South China coast have received little attention and have not been systematically documented (e.g. Li et al ., ; Li et al ., , ). These form the foci of the present study.…”

Complex networks for tracking extreme rainfall during typhoons

“…These factors are closely linked to the angular deviation of maximum radial ranks ϕ max i . When there is a large-scale vertical wind shear (e.g., in mid-latitudes, westerlies), a convection maximum is expected on the right hand side of the shear vector, 19,57 while a decrease in the velocity might enhance the rainfall intensity. 58 In the western North Pacific, most intense rains were observed on the right side of the eye due to the frictional convergence at the coastal terrains; wind retardation on the onshore side (creating surface convergence) and wind acceleration (creating surface divergence) on the offshore side.…”

“…16 Several approximately stationary long lasting downpour structures (rainbands) evolve around the eye-of-the-typhoon. 17,18 Rain structures around the eye wall up to 100 km are distributed nearly symmetrically, 19 and they behave asymmetrically in increasing distance from the eye. 20,21 The ETTs deviate from those of extreme rainfall and a proposed "docked inner rain shield" mainly within 150-250 km northeast to southeast of the eye, and a rarer "outer rain shield" up to 500 km northwest to southwest of the eye.…”