SEMINAR: Reminder: AOML Seminar - November 15, 2011- 10:00 a.m - Dr. George Bryan - “How to make simulated hurricanes look like observed hurricanes”

["Robert.Rogers" <Robert.Rogers@noaa.gov>]

AOML Seminar

 

DATE:            Tuesday, November 15, 2011

 

TIME:              10:00 a.m. – refreshments at 9:45 a.m.

 

Location:  AOML First Floor   Conference Room

 

SPEAKER:      Dr. George Bryan,

                         National Center for Atmospheric Research

 

TITLE:           “How to make simulated hurricanes look 

                        like observed hurricanes”

Abstract:  Among the many uncertainties in numerical and theoretical 

models of hurricanes, perhaps the greatest uncertainty lies in the 

parameterizations of boundary-layer turbulence and air-sea exchange. 

In an attempt to reduce this uncertainty, I have conducted a very 

large set of idealized simulations of strong hurricanes (Category 4+). 

The simulations vary only in the specification of surface (10-m) 

exchange coefficients and/or length scales in a turbulence 

parameterization.  To determine which simulation, among the hundreds 

conducted, is most realistic, I have examined several simple yet 

well-observed metrics of hurricane intensity and structure, such as: 

maximum possible wind;  minimum possible pressure;  surface 

wind-pressure relationship;  height of maximum wind;  and surface 

inflow angle.  An optimal set of values for exchange coefficients and 

turbulence length scales emerges from this analysis, and these values 

are reasonably consistent with recent observational and laboratory 

studies.  Using this information, I also explain why Emanuel (1995) 

concluded that the ratio of surface exchange coefficients for enthalpy 

and drag (Ce/Cd) is likely about 0.75 in strong hurricanes, and why 

more recent work suggests this ratio is probably about 0.5.

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