So, in my ongoing quest to make the DDTs perform non-ridiculously, I realized that the joint phenology/hydrology system is being fundamentally thrown off by the very dry initialization of soil moisture, which is set as VWC of 0.15 in the init_cold routine here:
https://github.com/ESCOMP/CTSM/blob/e33b4658f6c51f8d1cce4ed1986bc3dc28014c5d/src/biogeophys/WaterStateType.F90#L773
What happens after the initialization is that
- The soil is dry, and so the leaves come off and stay off for a long time
- when they come back on, they've lost so much carbon that they die off (of carbon starvation and then termination).
- when the few survivors try to regrow, they can't pull the soil moisture down far enough to trigger the normal drought deciduous behaviour and get stuck in a perma-wet situation
- in the perma-wet situation, they are further penalized for there being no dry season.
- they also have extremely low GPP, LAI, biomass etc.
In this way, most of the savanna areas have been dying in large semi-arid areas of my simulations. e.g.
https://github.com/rosiealice/global_pft_scripts/blob/master/analysis_scripts/droughtdec_init0.15.ipynb
Changing the initial soil moisture value to 0.85 massively improves things, as shown in:
here:https://github.com/rosiealice/global_pft_scripts/blob/master/analysis_scripts/droughtdec_initw.ipynb
If you look at the last figure in these notebooks, of SMP and VWC across soil layers, you can see that in the 0.15 simulation, the system is still not at equilibrium well into the second year. For many hydrology applications that's fine of course, but for these DDT's with their carbon stores and their mortality thresholds, it really isn't.
If you look at the first plot (of LAI in each season) to illustrate the impact that changing soil moisture initialization has on the DDT dynamics!
So, my question is, slightly directed at @dlawrenncar and Sean Swenson (who isn't here, but i'll direct him to this later), is there a reason to not modify the initial soil moisture? I can imagine several (flooding, GRACE comparison, permafrost concerns, hydraulic redistribution etc.) Of course this change can go in with a 'use_fates' caveat, and I see it's already been done for cases with HYDRO, but is there any reason not to do this? I imagine that this might also be messing a little bit (but not as much, in the absence of mortality and with the magic of XSMR).
Anyway, with this change, everything makes a lot more sense, thankfully...
n.b. that in these notebooks for some reason the first year took forever to read in, and my newby python skills haven't managed to fix this yet. In general, reading in more than 2-3 years of these daily output files takes forever...
So, in my ongoing quest to make the DDTs perform non-ridiculously, I realized that the joint phenology/hydrology system is being fundamentally thrown off by the very dry initialization of soil moisture, which is set as VWC of 0.15 in the init_cold routine here:
https://github.com/ESCOMP/CTSM/blob/e33b4658f6c51f8d1cce4ed1986bc3dc28014c5d/src/biogeophys/WaterStateType.F90#L773
What happens after the initialization is that
In this way, most of the savanna areas have been dying in large semi-arid areas of my simulations. e.g.
https://github.com/rosiealice/global_pft_scripts/blob/master/analysis_scripts/droughtdec_init0.15.ipynb
Changing the initial soil moisture value to 0.85 massively improves things, as shown in:
here:https://github.com/rosiealice/global_pft_scripts/blob/master/analysis_scripts/droughtdec_initw.ipynb
If you look at the last figure in these notebooks, of SMP and VWC across soil layers, you can see that in the 0.15 simulation, the system is still not at equilibrium well into the second year. For many hydrology applications that's fine of course, but for these DDT's with their carbon stores and their mortality thresholds, it really isn't.
If you look at the first plot (of LAI in each season) to illustrate the impact that changing soil moisture initialization has on the DDT dynamics!
So, my question is, slightly directed at @dlawrenncar and Sean Swenson (who isn't here, but i'll direct him to this later), is there a reason to not modify the initial soil moisture? I can imagine several (flooding, GRACE comparison, permafrost concerns, hydraulic redistribution etc.) Of course this change can go in with a 'use_fates' caveat, and I see it's already been done for cases with HYDRO, but is there any reason not to do this? I imagine that this might also be messing a little bit (but not as much, in the absence of mortality and with the magic of XSMR).
Anyway, with this change, everything makes a lot more sense, thankfully...
n.b. that in these notebooks for some reason the first year took forever to read in, and my newby python skills haven't managed to fix this yet. In general, reading in more than 2-3 years of these daily output files takes forever...