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MPIBGC-TEE / bgc_md2

New development version of the biogeochemical model database bgc_md
GNU General Public License v3.0
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SDGVM explodes with delta_t_val>1 #105

Open viatkin opened 2 years ago

viatkin commented 2 years ago

Hi Aneesh!

I already added your model to the comparison, however, I noticed that it only works with iterator step (delta_t_val) of 1 day (which makes everything extremely slow). I tried changing it to several days, but every time (even with delta_t_val=2) the model explodes - it starts producing extremely high and extremely low values that eventually cause an overflow. I noticed that in your forward run function (param2res) delta_t_val=1, while in all other models delta_t_val=15 to speed up data assimilation. When I tried changing delta_t_val in param2res, it also caused output to explode. Do you know what might be the reason? We should fix it to make the model run fast.

Thanks!

viatkin commented 2 years ago

Apparently bad parameters cause increasingly strong oscillations of the microbial pool, resulting in negative and impossibly large values when the step size is more than 1 day. 2 solutions to explore: 1) Improve model parametrization using original equations for fluxes from A. Walker. 2) Use differential equation solver with automatically adjusted step size.