Animate location (or strength?) of alpha / opacity mask to suggest motion along arrows I have a globe depicting trade winds:


The trade wind arrows are an image with alpha.


I am in cycles, using this node tree for the earth material:


I would like to animate the opacity of the arrows from less visible to more visible in a conveyor-belt manner, or in "waves", suggesting motion from the south to the north. The point is to emphasize the motion of the trade winds along the image.

The north and south trade winds are on a single image. I can make them separate if a solution requires... as I only want to animate the arrows in the southern hemisphere.
I would start by adding something like this node set up where my Diffuse BSDF is your Diffuse shader after the Trade_Winds11 Image Texture and it all goes into the following Mix node.

In my example animating the Z Location in the Mapping node will cause that black line (hopefully alpha as it is running through a transparent shader) to move up or down. You can really play with the Mapping node to get the lines from the wave texture to move how you'd like.

I hope this helps.