Configuring DAISY for SSOC SVAT + Ball-Berry Model and Direct/Diffuse Radiation Inputs?

[Magnus Kamau Katana Lindhardt]

Dear DAISY community,

I'm working on simulating highly dynamic microclimates under vertical agrivoltaic systems using DAISY, with a particular focus on spatiotemporal fluctuations in light/shade, temperature, VPD, etc. I would greatly appreciate clarification on the following points related to the SVAT model selection and radiation variables inputs.

Context:

• I have hourly weather data files for each of my microclimate scenarios.

• Each file contains: AirTemp, VapPres, WindSpeed, GlobRad, Precip, RefEvap, and also measured RadDiffuse, RadDirect, Humidity, and WindDirection from in-field sensors.

• I want to enable the most detailed SVAT model available in DAISY— Model 3, described in Ch. 1: System and Modelling Concepts — that:

  • Separately models sunlit and shaded leaf surfaces

  • Couples energy, radiation, and water fluxes

  • Uses a Ball–Berry type stomatal conductance model, accounting for leaf-level dynamics and chemical signalling (ABA)

  • Has leaf temperature, CO₂ pressure, and vapour pressure as state variables

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Questions:

1. How do I activate the SSOC SVAT model in my DAISY setup?

• Where can I add this to the setup?

  (Bioclimate original (svat SSOC) (raddist sun-shade))

• What other components must be configured to support the SSOC model?

• Can state variables like leaf temperature, leaf CO₂, and VPD at the leaf surface be used for calibration or diagnostics?

• How do I handle the detailed input requirements (photosynthesis, ABA) when using this model 3 in my simulations?

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2. Radiation: Can I directly supply diffuse and global radiation in my weather file?

• In SAFIR Deliverable D3.2 (https://daisy.ku.dk/projects-and-collaboration/projects/safir/D3_2.pdf), it is mentioned that DAISY’s internal DifRad model estimates the fraction of diffuse PAR if not provided. But since I already measure RadDiffuse, so can I simply include both GlobRad and RadDiffuse (or RadDiffuse and RadDirect (W/m²) in the input weather file, and will DAISY use these directly?

• Is it correctly understood that the fraction of Diffuse/Global radiation determines the diffuse PAR / direct PAR fraction used internally?

• Do I need to specify PAR explicitly, or will DAISY internally convert GlobRad and/or RadDiffuse and RadDirect to PAR fractions?

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Any insights on how to implement this would be very helpful. I aim to capture the physiological and biophysical responses of crops in solar panel shade vs. open field, especially for yield, ET and soil water dynamics.

Thank you in advance!

Best regards,
Kamau Lindhardt

[Per Abrahamsen]

Hi Kamau

Right now Laura has a much more recent knowledge than me, I'll try to answer what I can and maybe she can correct me.

On Thu, Jul 24, 2025 at 3:16 PM Magnus Kamau Katana Lindhardt <kamauli...@gmail.com> wrote:

• Each file contains: AirTemp, VapPres, WindSpeed, GlobRad, Precip, RefEvap, and also measured RadDiffuse, RadDirect, Humidity, and WindDirection from in-field sensors.

We still use RefEvap for calculation of evaporation from free water (e.g. ponding), even though SSOC gives a far better way to calculate transpiration and soil evaporation.

• Uses a Ball–Berry type stomatal conductance model, accounting for leaf-level dynamics and chemical signalling (ABA)

I do not suggest using ABA, the models that include ABA don't perform better than the models that ignore it.

• • Has leaf temperature, CO₂ pressure, and vapour pressure as state variables

Techincally they are log variables, their values don't tranfer over timesteps.

1. How do I activate the SSOC SVAT model in my DAISY setup?

• Where can I add this to the setup?

  (Bioclimate original (svat SSOC) (raddist sun-shade))

(Bioclimate SSOC) ;; the prefered way to enable the various submodels related to the SSOC model.

 

• What other components must be configured to support the SSOC model?

You need crop that use the Farquhar  photosynthesis model.

• Can state variables like leaf temperature, leaf CO₂, and VPD at the leaf surface be used for calibration or diagnostics?

Maybe?  They can be logged, but I haven't tried using them for calibration. 

• How do I handle the detailed input requirements (photosynthesis, ABA) when using this model 3 in my simulations?

I guess you need to take one of the existing Farquhar calibrations, and  fit it with your data.  I have never done so. Laura will know better.

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2. Radiation: Can I directly supply diffuse and global radiation in my weather file?

• In SAFIR Deliverable D3.2 (https://daisy.ku.dk/projects-and-collaboration/projects/safir/D3_2.pdf), it is mentioned that DAISY’s internal DifRad model estimates the fraction of diffuse PAR if not provided. But since I already measure RadDiffuse, so can I simply include both GlobRad and RadDiffuse (or RadDiffuse and RadDirect (W/m²) in the input weather file, and will DAISY use these directly?

You can specify "DiffRad" in the weather file.

 

• Is it correctly understood that the fraction of Diffuse/Global radiation determines the diffuse PAR / direct PAR fraction used internally?

PAR is a fixed fraction of global radiation.

• Do I need to specify PAR explicitly, or will DAISY internally convert GlobRad and/or RadDiffuse and RadDirect to PAR fractions?

You can not specify PAR directly , the fraction of PAR in global radiation is hard coded.

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Any insights on how to implement this would be very helpful. I aim to capture the physiological and biophysical responses of crops in solar panel shade vs. open field, especially for yield, ET and soil water dynamics.

Good luck!  It is really a complicated part of Daisy.

 

Kindly,

Per