scholarly journals An analytical model on the simulation of the wind field in a typhoon boundary layer

1993 ◽  
Vol 1993 (57) ◽  
pp. 1-14
Author(s):  
Yen MENG ◽  
Masahiro MATSUI ◽  
Kazuki HIBI
Keyword(s):  
Boundary Layer ◽  
Analytical Model ◽  
Wind Field

The Evolution of Asymmetries in the Tropical Cyclone Boundary Layer Wind Field during Landfall

2021 ◽  
Keyword(s):  
Boundary Layer ◽  
Tropical Cyclone ◽  
Wind Field ◽  
Surface Wind ◽  
Frictional Stress ◽  
Homogeneous Surface ◽  
Sudden Decrease ◽  
The Right ◽  
Tropical Cyclone Boundary Layer

Abstract The evolution of the tropical cyclone boundary layer (TCBL) wind field before landfall is examined in this study. As noted in previous studies, a typical TCBL wind structure over the ocean features a supergradient boundary layer jet to the left of motion and Earth-relative maximum winds to the right. However, the detailed response of the wind field to frictional convergence at the coastline is less well known. Here, idealized numerical simulations reveal an increase in the offshore radial and vertical velocities beginning once the TC is roughly 200 km offshore. This increase in the radial velocity is attributed to the sudden decrease in frictional stress once the highly agradient flow crosses the offshore coastline. Enhanced advection of angular momentum by the secondary circulation forces a strengthening of the supergradient jet near the top of the TCBL. Sensitivity experiments reveal that the coastal roughness discontinuity dominates the friction asymmetry due to motion. Additionally, increasing the inland roughness through increasing the aerodynamic roughness length enhances the observed asymmetries. Lastly, a brief analysis of in-situ surface wind data collected during the landfall of three Gulf of Mexico hurricanes is provided and compared to the idealized simulations. Despite the limited in-situ data, the observations generally support the simulations. The results here imply that assumptions about the TCBL wind field based on observations from over horizontally-homogeneous surface types - which have been well-documented by previous studies - are inappropriate for use near strong frictional heterogeneity.

scholarly journals An Analytical Model for the Regeneration of Wind after Exiting a Wind Farm

Energies ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 2071
Author(s):  
Brian Fiedler
Keyword(s):  
Boundary Layer ◽  
Pressure Gradient ◽  
Atmospheric Boundary Layer ◽  
Linear Model ◽  
Analytical Model ◽  
Environmental Conditions ◽  
Wind Farm ◽  
Length Scale ◽  
Equilibrium Calculation ◽  
Friction Pressure

The simplest model for an atmospheric boundary layer assumes a uniform steady wind over a certain depth, of order 1 km, with the forces of friction, pressure gradient and Coriolis in balance. A linear model is here employed for the adjustment of wind to this equilibrium, as the wake of a very wide wind farm. A length scale is predicted for the exponential adjustment to equilibrium. Calculation of this length scale is aided by knowledge of the angle for which the wind would normally cross the isobars in environmental conditions in the wake.

scholarly journals Wind Profile and Drag Coefficient over Mature Ocean Surface Wave Spectra

2004 ◽  
Vol 34 (11) ◽  
pp. 2345-2358 ◽  
Author(s):  
Tetsu Hara ◽  
Stephen E. Belcher
Keyword(s):  
Boundary Layer ◽  
Surface Wave ◽  
Drag Coefficient ◽  
Analytical Model ◽  
Wind Profile ◽  
Momentum Conservation ◽  
Wave Drag ◽  
Wave Spectra ◽  
Wave Boundary Layer ◽  
Wave Boundary

Abstract The mean wind profile and the Charnock coefficient, or drag coefficient, over mature seas are investigated. A model of the wave boundary layer, which consists of the lowest part of the atmospheric boundary layer that is influenced by surface waves, is developed based on the conservation of momentum and energy. Energy conservation is cast as a bulk constraint, integrated across the depth of the wave boundary layer, and the turbulence closure is achieved by parameterizing the dissipation rate of turbulent kinetic energy. Momentum conservation is accounted for by using the analytical model of the equilibrium surface wave spectra developed by Hara and Belcher. This approach allows analytical expressions of the Charnock coefficient to be obtained and the results to be examined in terms of key nondimensional parameters. In particular, simple expressions are obtained in the asymptotic limit at which effects of viscosity and surface tension are small and the majority of the stress is supported by wave drag. This analytical model allows us to identify the conditions necessary for the Charnock coefficient to be a true constant, an assumption routinely made in existing bulk parameterizations.

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