colormap confusion - continent color & colormap options

   I am new to NCL and trying to start simple, by drawing a base map of
the tropical Atlantic. I am playing with color tables because (1) I
want to have a very light grey lat/lon grid and (2) I'm going to want to
put things on the base map eventually. I'm using NCL v5.0.1 on a Mac
OSX system on which I have no adminstrator priviledges. I've got 1
question and 1 problem.

   The question: When I look in my $NCARG_ROOT/lib/ncarg/colormaps, I do
not see any of the following gray scale colormaps: gsdtol,
gsltod_default, gscyclic (c.f.
www.ncl.ucar.edu/Document/Graphics/ColorTables/grayscale_gr.shtml). Why
is this? are they kept somewhere else?

   The problem: Given the following key lines of code:
=====
   wks = gsn_open_wks("ps","TropAtlantic")

; gsn_define_colormap(wks,"gui_default") ; *.rgb file
; gsn_define_colormap(wks,"rainbow+gray") ; *.gp file
; gsn_define_colormap(wks,"so4_23") ; *.gp file
; gsn_define_colormap(wks,"amwg") ; *.rgb file

   map = gsn_csm_map_ce(wks,mpres)
=====
- when I run this code with no call to gsn_define_colormap (thus using
*wkColorMap : rainbow+gray
from my .hluresfile, I get grey land and a white ocean.

- when I run this code with gsn_define_colormap(wks,"gui_default"), an
ncolors=24 rainbow with no gray, I get no visible land and a white ocean.

- when I run this code with an explict call matching my .hluresfile,
gsn_define_colormap(wks,"rainbow+gray"), I get grey land and a white ocean.

- when use gsn_define_colormap(wks,"so4_23"), another small (ncolors=25)
rainbow with no gray, I get light pink land and a white ocean! I
printed the output and the color table from www.ncl.ucar.edu, and it
looks to me as if the land is color #23 (251,211,251).

- when use gsn_define_colormap(wks,"amwg"), one more small (ncolors=18)
rainbow with no gray, I get powder blue land. Comparing printed plot &
color table, it looks like color #6 (176,224,230).

   What's going on? The documentation for gsn_csm_map_ce says "the
following will happen automatically: the continents will be colored gray
...". Is this only true if the colormap in play has a gray? If I want
to plot something using a grey-free colormap on top of gray continents,
do I need to switch colormaps midstream?

Cheers,
   Leslie

--
Dr. Leslie M. Hartten
CIRES, Univ. of Colorado       email: Leslie.M.Hartten_at_noaa.gov
216 UCB                        web:   http://cires.colorado.edu/~hartten
Boulder  CO  80309-0216        phone: (303)497-7052   fax: 497-6181
--
Disclaimer:  The contents of this message are mine personally and do not 
necessarily reflect any position of the Government of the United States 
of America, the National Oceanic and Atmospheric Administration, or the 
University of Colorado.
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