Indirect evaporative cooling using vegetation cover

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Hello, I am trying to develop a model in which i aim to verify the effect of the use of indirect evaporative cooling using vegetation cover on the ground right outside the building perimeter. It's in a dry weather region so the ideia is to compare the effect of a dry soil versus a grass one.

What should be the most effective way? The simple alteration of the soil moisture on GroundDomain should do the effect? Ou should I add a green roof surface on the ground?

I'm new to EnergyPlus so I apologize if there's an obvious solution that i'm not aware of.