Removing grass discoloring (ex. moving shading from clouds)

Hello!

Naturally in Unity, there seem to be moving shadows on grass (supposed to resemble shadows that are cast from clouds)

Is there any way to remove things like this? The terrain grass editor in Unity is not very customizable, would I have to script my own? If so, what is the "theory" behind it? Is it just instantiating of a plane with grass sprites on? I'd be very thankful if someone could show a short example script in either C# or JS! =)