SEMINAR: MPO Seminar: Dr. Mohamed Iskandarani,Wednesday, September 5, at 3:00 p.m, Slab seminar room, S/A 103

[Sandrine Apelbaum <sapelbaum@rsmas.miami.edu>]

MPO Seminar

Dr. Mohamed Iskandarani

 

“

Bayesian Inference of Drag Coefficient Parameters 

using AXBT data 

from Typhoon Fanapi

”

 

Room: Slab seminar room, S/A 103

Date: Wednesday, September 5, at 3:00 p.m.

abstract:

We introduce a three-parameter characterization of the wind-speed dependence of the drag coefficient and apply a Bayesian formalism to 
infer values for these parameters from AXBT temperature data obtained during Typhoon Fanapi. One parameter is a multiplicative factor that 
determines the drag coefficient saturation level, a second is the maximum wind speed at which drag coefficient saturation occurs, and the 
third is the rate of change of drag coefficient with increasing wind speed after saturation. Bayesian inference provides, in addition to 
optimal estimate of the parameters, a non-Gaussian probability distribution characterizing the uncertainty of these estimates.  The 
efficiency of our approach stems from the use of adaptive polynomial expansions to build an inexpensive surrogate for the high-resolution 
numerical model that couples simulated winds to the oceanic temperature data, dramatically reducing the computational burden of the Markov Chain 
Monte-Carlo sampling. Our results indicate that the most likely values for the drag coefficient saturation and the corresponding wind speed are 
about 2.3 x 10-3 and 34 m/s, respectively; the data was not informative regarding the drag coefficient behavior at higher wind speeds.

Sandrine Apelbaum

Meteorology and Physical Oceanography 
Rosenstiel School of Marine and Atmospheric Science
University of Miami
4600 Rickenbacker Causeway
Miami, FL 33149-1098
Tel     (305) 421-4057
Fax     (305) 421-4696

sapelbaum@rsmas.miami.edu