scholarly journals Improving hurricane boundary layer parameterization scheme based on observations

2021 ◽  
Author(s):  
Sundararaman Gopalakrishnan ◽  
Andrew Hazelton ◽  
Jun A. Zhang
Keyword(s):  
Boundary Layer ◽  
Parameterization Scheme ◽  
Hurricane Boundary Layer

Finescale Dual-Doppler Analysis of Hurricane Boundary Layer Structures in Hurricane Frances (2004) at Landfall

2014 ◽  
Vol 142 (5) ◽  
pp. 1874-1891 ◽  
Author(s):  
Karen A. Kosiba ◽  
Joshua Wurman
Keyword(s):  
Boundary Layer ◽  
Three Dimensional ◽  
Transient Nature ◽  
Layer Structures ◽  
Characteristic Wavelength ◽  
Doppler Data ◽  
Mean Wind Speed ◽  
Average Flux ◽  
Hurricane Boundary Layer ◽  
The Right

Abstract Two Doppler on Wheels (DOW) mobile radars collected fine-spatial-scale dual-Doppler data in the right-front quadrant and eye of Hurricane Frances (2004) as it made landfall near Stuart, Florida. A 5.7-km dual-Doppler baseline established a dual-Doppler domain south and east of Fort Pierce, Florida, encompassing a 5.5 km × 5.5 km horizontal area, with a grid spacing of 20 m, allowing for the resolution of subkilometer-scale horizontal structures and associated kinematics. Three-dimensional vector wind analyses of the boundary layer revealed the presence of linear coherent structures with a characteristic wavelength of 400–500 m near the surface that increased in size and became more cellular in shape with increasing height. Average horizontal perturbation winds were proportional to average total horizontal winds. Within the eye of the hurricane, the features lost linear coherency despite a high mean wind speed, possibly due to changes in stability. A slight decrease in the characteristic wavelength of boundary layer structures was documented as the winds cross the barrier islands east of Fort Pierce. Vertical flux of horizontal momentum caused by individual vortical structures was substantially higher than values employed in turbulence parameterization schemes, but the domain-wide average flux was substantially lower than that in individual structures, likely due to the transient nature of the most intense portions of the structures. Analysis of the turbulent kinetic energy (TKE) yielded values comparable to those reported in previous observational studies over the open ocean. However, there was substantial variability in TKE within the dual-Doppler domain, emphasizing the challenge in obtaining representative samples using non-3D measurements such as dropsondes.

scholarly journals Effects of Vertical Eddy Diffusivity Parameterization on the Evolution of Landfalling Hurricanes

2017 ◽  
Vol 74 (6) ◽  
pp. 1879-1905 ◽  
Author(s):  
Feimin Zhang ◽  
Zhaoxia Pu
Keyword(s):  
Boundary Layer ◽  
Vertical Mixing ◽  
Eddy Diffusivity ◽  
Essential Components ◽  
Moisture Fluxes ◽  
Layer Velocity ◽  
Hurricane Boundary Layer ◽  
Heat And Moisture ◽  
Vertical Eddy Diffusivity ◽  
Vertical Eddy

Abstract As a result of rapid changes in surface conditions when a landfalling hurricane moves from ocean to land, interactions between the hurricane and surface heat and moisture fluxes become essential components of its evolution and dissipation. With a research version of the Hurricane Weather Research and Forecasting Model (HWRF), this study examines the effects of the vertical eddy diffusivity in the boundary layer on the evolution of three landfalling hurricanes (Dennis, Katrina, and Rita in 2005). Specifically, the parameterization scheme of eddy diffusivity for momentum Km is adjusted with the modification of the mixed-layer velocity scale in HWRF for both stable and unstable conditions. Results show that the change in the Km parameter leads to improved simulations of hurricane track, intensity, and quantitative precipitation against observations during and after landfall, compared to the simulations with the original Km. Further diagnosis shows that, compared to original Km, the modified Km produces stronger vertical mixing in the hurricane boundary layer over land, which tends to stabilize the hurricane boundary layer. Consequently, the simulated landfalling hurricanes attenuate effectively with the modified Km, while they mostly inherit their characteristics over the ocean and decay inefficiently with the original Km.

scholarly journals Effects of Boundary Layer Vertical Mixing on the Evolution of Hurricanes over Land

2017 ◽  
Vol 145 (6) ◽  
pp. 2343-2361 ◽  
Author(s):  
Feimin Zhang ◽  
Zhaoxia Pu ◽  
Chenghai Wang
Keyword(s):  
Boundary Layer ◽  
Positive Impact ◽  
Potential Temperature ◽  
Vertical Mixing ◽  
Vertical Wind Shear ◽  
Vertical Gradient ◽  
Weather Research And Forecasting ◽  
Virtual Potential Temperature ◽  
Dynamic Structures ◽  
Hurricane Boundary Layer

Abstract After a hurricane makes landfall, its evolution is strongly influenced by its interaction with the planetary boundary layer (PBL) over land. In this study, a series of numerical experiments are performed to examine the effects of boundary layer vertical mixing on hurricane simulations over land using a research version of the NCEP Hurricane Weather Research and Forecasting (HWRF) Model with three landfalling hurricane cases. It is found that vertical mixing in the PBL has a strong influence on the simulated hurricane evolution. Specifically, strong vertical mixing has a positive impact on numerical simulations of hurricanes over land, with better track, intensity, synoptic flow, and precipitation simulations. In contrast, weak vertical mixing leads to the strong hurricanes over land. Diagnoses of the thermodynamic and dynamic structures of hurricane vortices further suggest that the strong vertical mixing in the PBL could cause a decrease in the vertical wind shear and an increase in the vertical gradient of virtual potential temperature. As a consequence, these changes destroy the turbulence kinetic energy in the hurricane boundary layer and thus stabilize the hurricane boundary layer and limit its maintenance over land.

A quasi-empirical model of the hurricane boundary layer

1974 ◽  
Vol 79 (21) ◽  
pp. 3033-3040 ◽  
Author(s):  
Russell L. Elsberry ◽  
Nils A. S. Pearson ◽  
Leino B. Corgnati
Keyword(s):  
Boundary Layer ◽  
Empirical Model ◽  
Hurricane Boundary Layer

scholarly journals On the Characteristics of Linear-Phase Roll Vortices under a Moving Hurricane Boundary Layer

2018 ◽  
Vol 75 (8) ◽  
pp. 2589-2598 ◽  
Author(s):  
Kun Gao ◽  
Isaac Ginis
Keyword(s):  
Boundary Layer ◽  
Growth Rate ◽  
Shear Layer ◽  
Wind Shear ◽  
Horizontal Distribution ◽  
Linear Phase ◽  
Layer Depth ◽  
Bottom Boundary ◽  
Roll Vortices ◽  
Hurricane Boundary Layer

Abstract Previous theoretical and numerical studies only focused on the formation of roll vortices (rolls) under a stationary and axisymmetric hurricane. The effect of the asymmetric wind structure induced by the storm movement on the roll characteristics remains unknown. In this study, we present the first attempt to investigate the characteristics of linear-phase rolls under a moving hurricane by embedding a linear two-dimensional (2D) roll-resolving model into a 3D hurricane boundary layer model. It is found that the roll horizontal wavelength under the moving hurricane is largely determined by the radial-shear-layer depth, defined as the thickness of the layer with positive radial wind shear. The horizontal distribution of the roll wavelength resembles the asymmetric pattern of the radial-shear-layer depth. Interestingly, the roll growth rate is not only affected by the radial wind shear magnitude alluded to in previous studies but also by the radial-shear-layer depth. A deeper (shallower) radial shear layer tends to decrease (increase) the roll growth rate. Such an effect is due to the presence of the bottom boundary. The bottom boundary constrains the lower-level roll streamlines and reduces the efficiency of rolls in extracting kinetic energy from the radial shear. This effect is more pronounced under a deeper shear layer, which favors the formation of larger-size rolls. This study improves the understanding of the main factors affecting the structure and growth of rolls and will provide guidance for interpreting the spatial distribution of rolls under realistic hurricanes in observations and high-resolution simulations.

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