claudiofgcardoso
commented
4 years ago I think I get it now. In your paper you define Tw as "the half-life for debris to remain on the beach before being washed off again". Liubartseva et al. (2018) also defines particle half-life as "the mean retention time on the beach" (Tcst in that specific case-study). Taking both definitions into consideration, I assumed that Tw was referring to the average retention time a particle would stay on the beach before being washed off. However, In Dominics et al. (2013) there are two parameters for particle half-life which are used for two distinct probability functions:
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Ts = "Half-life for absorption on coast": used in "For the “beached” particles, the particle non-evaporative oil component is then reduced to
(...) Ts(Li) is a half-life for seepage or any other mode of permanent attachment to the coasts. Half-life is a parameter which describes the “absorbency” of the shoreline by describing the rate of entrainment of oil after it has landed at a given shoreline (Shen et al., 1987)." -
Tw = Half-life for washing off coast: used in "The beaching of a particle may not be permanent and it is assumed that at subsequent time steps there is a probability that the parcel may be washed back into the water (Shen et al., 1987; Al-Rabeh et al., 2000). The probability of wash-back is given by:
where Tw(Li) is the half-life of beached oil before it is washed off again."
Now, taking all this into consideration, the usage of the probability function for beaching of particles in TrackMPD makes perfect sense if we regard particle half-life as Ts instead of Tw. Do you agree?
References: De Dominicis, M., Pinardi, N., Zodiatis, G., & Lardner, R. (2013). MEDSLIK-II, a Lagrangian marine surface oil spill model for short-term forecasting-Part 1: Theory. Geoscientific Model Development, 6(6), 1851–1869. https://doi.org/10.5194/gmd-6-1851-2013
Liubartseva, S., Coppini, G., Lecci, R., & Clementi, E. (2018). Tracking plastics in the Mediterranean: 2D Lagrangian model. Marine Pollution Bulletin, 129(1), 151–162. https://doi.org/10.1016/j.marpolbul.2018.02.019
Hello Isabel,
First of all, congratulations and thank your for this tool! It surely helps elucidate how several physical properties can change the dynamics of the particles..
Concerning the beaching of these particles, I want to focus on the Monte Carlo approach with probability P of being washed-off: the increase of the particle half-life (or mean retention period) for the particle to remain on the beach before being washed off (parameter Tw) again also increases the probability of particles to be washed-off. I'm finding this pattern very difficult to understand...
I prepared this graph in which we can see how the probability P of particle to be washed off decreases exponentially with time. This makes perfect sense. Now, the fact that the probability of a particle to be washed off remains higher for a longer period in particles which Tw is larger doesn't make much sense to me (legend represents particle Tw in days). As I see it, we should expect a lower probability of a particle to be washed off in particles with higher values of Tw... Can you help me with this?
Thanks! Cláudio