Start by opening an image that has some good area of sky.
Using rectagular selection tool create a selection.
Press Ctrl+Alt+D to feather the selection.
Select rainbow gradient.
Fill the selection with the gradient.
Right click the layer and select warp.
Adjust the nodes to create a semi circular shape.
Erase the area over the surface using erase tool.
Change the color mode of rainbow layer to overlay.
From layer palette reduce the opacity of rainbow layer to make it more subdued.
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