I have another one for you gurus. I am trying to model the output of a
particle-tracking model - this is a model in which the user drops a large
number (~5000) of neutrally-buoyant particles into a hydrodynamic model of
a tidal or river region and follows them over time. I am interested in
when the particles pass certain points. Once the particles are dropped in
the "water", they move with the mean flow (i.e., downstream) and also
disperse due to tidal action. The shape of the blob of particles is
stretched out by tidal dispersion, but this stretching is asymmetric so
that the upstream side of the distribution has a much heavier tail than the
downstream side. I plotted the cumulative fraction of particles passing
the control points, and the resulting graph therefore looks like a logistic
curve, but with a rapid initial acceleration and a very slow approach to
the asymptote. In some cases after 90 days the asymptote is still far in
the future.
Does anybody have a good idea of what would be a mathematically appropriate
curve to fit to data such as these?
Thank you.
Wim
======================
Dr. Wim Kimmerer
Research Professor of Biology
Romberg Tiburon Center
San Francisco State University
3152 Paradise Drive
Tiburon CA 94920
Ph. (415) 338-3515
Fax (415) 435-7120
http://online.sfsu.edu/~kimmerer/
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