Control over timing of outputs

[andrewwatford]

Question

Hi all,
I'm working on a project using parcels, where I advect passive particles through surface currents on an Arakawa A-grid. However, for the purposes of the project, I don't really care about all the particles' locations at regular intervals, but only when certain "events" occur - for example, arrival in a cell that is adjacent to land. When ParticleSet.execute() is called, it requires an outputdt argument that is fixed, which makes me think that this is not currently possible, and I haven't been able to find anything relevant in the docs (apologies if I've missed anything). Is there support in Parcels v3 for this kind of irregularly timed output, or do I have to subset some more regularly spaced output, or else write my own output functionality?
Thanks so much in advance!

[erikvansebille]

Thanks for your question, @andrewwatford. Unfortunately, the outputdt parameter indeed can only be one fixed value.

You can store an event on a particle using custom variables (e.g. particle.time_at_first_landing) and then write kernels to set these at the appropriate moment. If you then also write them out, you can select only these events in post-processing. This does mean of course that you'll write out much more data than you need, but I don't see a way around that I fear

[andrewwatford]

Thank you!