Syntax (not in expert window, but in Unix environment):

cat precip.ps sst.ps slp.ps > all.ps
overlay all.ps over.ps

Download:

Example: (converted to jpg for web viewing)

Troubleshooting:

Where precip.ps has colors over land, sst.ps has colors in the ocean, and slp.ps has contours. Can also have precip.ps colors over land, sstandslp.ps colors over ocean and contours together. Will only work all postscript fields are exact same size. May have to edit side labels as they will overlay also. Each postscipt can contain the preamble so they may be viewed individually before concatenation. Single bounding box of final product so can be used in LaTex to add title and color bars.