Open WPringle opened 1 month ago
Update on exploring... Here is an example for a 34-kt isotach at some time of Hurricane Florence:
The original Vr is in blue then I adjusted Vmax by increasing by 10% and reduced Rmax by 10%. Conserving the B parameter that was found to fit Vmax and r34 in the original curve, we get the new curve and r34
The equation used is simplified Holland model without Coriolis term. I think for our purposes here it can be a reasonable approximation:
alpha = (Rmax./r)^B;
Vr = Vmax*sqrt(exp(1-alpha).*alpha);
Another question is are the Rmax values in the track file actually used in GAHM? @pvelissariou1
Based on https://wiki.adcirc.org/Generalized_Asymmetric_Holland_Model and discussion with Taylor Asher it seems the Rmax is actually computed within GAHM for each quadrant.
One idea to test things by @andybpenny is to zero out all the radii values and run GAHM vs including the radii values and running with GAHM.
Presumably zeroing out the radii would result in a non-asymmetric GAHM type implementation but has advantage over classical Holland model in that it actually captures the true Vmax at low Rossby numbers:
where
Given a Rmax perturbation the GAHM isotachs are currently perturbed by the same absolute amount [n mi]
Let's revisit to see if we can adjust with more physical/theoretical basis , by e.g., preserving the "B" parameter of the GAHM model.