USE etopo20

! set up ocean mask
def axis/x=-1:360:0.3333/units=longitude xlon
def axis/y=90s:90n:0.3333/units=latitude ylat
def grid/x=xlon/y=ylat grd
let myrose = rose[g=grd]

! add the appropriate one below to other scripts that call this one
!shade/pal=black/o if(myrose ge 0) then 1 ! for land mask
!shade/pal=white/o if(myrose le 0) then 0 ! for ocean mask