Scale (km)

1
1800
180
18
1.8
0.18
0.018
Scale (km)
Van de Hoven
100 m
Operational model Grid-size

• Can current boundary layer turbulence
• parameterization schemes realistically
• represent the turbulent transport in high
• hurricane wind conditions?
• How can we predict the HBL organized
• structures and the associated damaging
• winds for hurricane wind damage
• Mitigation?

clouds
turbulence
Parameterization
Large eddy simulation
2
Classic Large eddy simulation (LES)

• Simulation domain cannot be very large, typically
  about tens of kilometers.
• Initialized with idealized vertical profiles and
  forced with uniform surface conditions and
  horizontal homogeneous large-scale atmospheric
  forcings.

• Hurricane vortex is a moving target.
• Swirling hurricane wind changes the speed and
  direction continuously.

Classic LES cannot be used to study HBL
3
WRF large-eddy simulation (WRF-LES)
Hurricane Ivan
Portable Wind Tower (PWT)
4

• The problem can be solved by increasing model
  resolution so that small scale processes, such as
  large turbulent eddies and clouds, are explicitly
  resolved.
• LES can be executed in a weather forecasting mode
  by nesting an LES domain in mesoscale models (Zhu
  2007).
• Such multi-scale simulations open the door to
  simulate background flow, hurricane vortex, and
  down to turbulent eddies in a unified system.
• PROPOSAL Developmen of a multi-scale
  modeling system from Weather Forecast Research
  (WRF) model including an online LES domain to
  explicitly simulate large turbulent eddies in a
  weather forecasting mode.