One way to do this would be to define a land/ocean mask using the etopo files that come with ferret. E.g.
let isOcean = if rose[d=1] le 0 then 1
You could then combine this with your own calculation below just to get the ocean region you want. I would use “shade” to fill in the missing data here.
Hope this helps,
On 3 Feb 2015, at 09:11, Steeven Paul Yerraguntla <steevenpaul@xxxxxxxxx> wrote: