Posted by Takuji Waseda on November 08, 2000 at 15:48:25:
In Reply to: Comments on poster posted by Eric Chassignet on November 07, 2000 at 07:51:27:
Dear Dr. Chassignet,
We thank you for your valuable comments.
Presented in this poster are analyses of the best numerical simulation from five similar runs conducted. The illustration of these test results was not included in this poster, and, in replying to your questions, we would certainly be able to explain some details.
: - I would have liked to see a stronger discussion of the observations:
: 1. How is the mean that is added to the TOPEX anomalies calculated?
: Are the results strongly sensitive to its choice?
: 2. You show an example that match the numerical results. The SSH
: movie seems to show that other scenarios may also take place.
: It would be nice to document each event and the possible source.
The mean comes from the time average of the model data similar to Ezer and Mellor (1994). We would think that the results are sensitive to the choice of the mean but in the series of runs conducted, a fixed value was used.
In the five tests conducted, we had varied the strength of the assimilations. Effectively, this change had caused variation in the thermocline displacement(between 130 m to 160 m) but not in the radius of the eddy (180 km). The resulting eddies had Rossby numbers between 0.012 and 0.014. Despite the small change in their scale, eddies behaved distinctly, two cases propagating westward causing the meander and the others made a sudden southern migration and no meander was triggered. One of the former cases is what we analyzed in this poster. The latter cases were found to have some similarity to the behavior of an anticyclonic eddy that was observed above Izu ridge in 1994; the observed eddy seemed to have made a sudden migration and did not cause the Kuroshio to meander. We have illustrated the distinct evolutions of eddies tested in the manuscript under preparation.
: - The numerical simulations are quite viscous (i.e. not eddy activity).
: Western boundary current can be unstable (Berloff and McWilliams, JPO
: 2000) and generate meanders as observed. Have you tried adding a
: small perturbation in the boundary current transport? This can
: also create a meander (see Stern and Chassignet, 2000, JMR).
Thank you for introducing us about your work. We have conducted an experiment increasing temporarily the Kuroshio inflow rate at the western boundary. This certainly resulted in a vacillation of the Kuroshio path but was insufficient to cause a large meander as discussed in this poster. However, it is too early to conclude anything from this preliminary study.
We will reply to your other comments later.
Takuji Waseda