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How to modify crop simulation parameters?

ShirleyX

New Member
Hi guys~
I am using "CLM5.0_BGCcrop" to simulate the NEE of the crop( irrigation and rotation) .
There is a difference between the simulated value and the measured value. Should I modify the phenology(e.g. CNPhenologyMod.F90) of rotation crop to improve the simulation accuracy .

Looking forward to your reply.
 

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dll@ucar_edu

Danica Lombardozzi
New Member
Hi Shirley,

Modifying the crop phenology might improve the seasonal cycle of NEE. Have you compared the observed and simulated planting dates? This will help to identify whether planting date is causing the mismatch.

In CLM, the phenology is calculated based on temperature thresholds. I see two ways of potentially adjusting this: through parameter file changes, or code changes. In the parameter file, you can adjust the GDD temperature thresholds for one or more phases, and/or you can change the planting window dates. Keep in mind, though, that this will likely require some testing and won't necessarily always match observations because the model will still predict the planting date. The second option is to specify the planting date based on observations in the model. CLM currently is not set up to do this, so it will require some code changes. It may be more work to do this at the start, but will give you more control over the timing of the phenology, so you have a better chance of matching the observed phenology.

Danica
 

ShirleyX

New Member
Hi Shirley,

Modifying the crop phenology might improve the seasonal cycle of NEE. Have you compared the observed and simulated planting dates? This will help to identify whether planting date is causing the mismatch.

In CLM, the phenology is calculated based on temperature thresholds. I see two ways of potentially adjusting this: through parameter file changes, or code changes. In the parameter file, you can adjust the GDD temperature thresholds for one or more phases, and/or you can change the planting window dates. Keep in mind, though, that this will likely require some testing and won't necessarily always match observations because the model will still predict the planting date. The second option is to specify the planting date based on observations in the model. CLM currently is not set up to do this, so it will require some code changes. It may be more work to do this at the start, but will give you more control over the timing of the phenology, so you have a better chance of matching the observed phenology.

Danica

Hi Danica,
Thank you very much for your help, I have been through the parameter file modified the largest planting dates, minimum date and crops mature maximum number of days (min_NH_planting_date max_NH_planting_date, mxmat), After modification , simulation of NEE seasonal cycle has been greatly improved , but I met another problem again, I found that the maximum LAI decreased after the modification of planting date (LAI = 1-2), is far less than the actual maximum (LAI = 5-6), which directly lead to simulate the NEE and ET value is less than the actual value.I tried to modify SLATOP to restore LAI to the actual size, but this would reduce the quality of the simulated NEE.How can I solve this problem?

Looking forward to your reply. Thank you ~
 

dll@ucar_edu

Danica Lombardozzi
New Member
Hi Shirley,

I somehow overlooked this question!

I'm not entirely surprised that changing the planting dates changes the magnitude of NEE and LAI because this also changes when the planting date and leaf emergence phases are and therefore the accumulation of GDD.

You may want to try adjusting some of the allocation parameters to allocate more to the leaf during the leaf emergence phase. I think the easiest way to do this is to change the allocation to the root parameter (arooti, I believe) during this phase, as the leaf allocation is calculated based on root allocation. If this doesn't work, it might also be useful to look at and adjust the GDD thresholds, as these will accumulate at different rates depending on the temperatures during the planting season.

I think you might be able to diagnose the problem easiest if you look at multiple related variables. For example, in addition to LAI, look at GPP, AR, CPHASE, biomass for each of the plant pools. If GPP is low because temperatures are cold for photosynthesis, then the plant won't be assimilating enough carbon to grow leaves.

Danica
 
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