I believe it is masked for the sky then brightness/contrast layer(s) in your processing? My only problem with that it is the sky is now darker than the ground... and it seems like you have tonemapped the ground? Either way it has the oversharpened sort of look to it.
On your composition... horizon has landed in the middle...
try not to make the horizontal line fall even in the composition. however nice photo
______________________________________________________________________ Chun Keang Photography
______________________________________________________________________