Masking fields by topography

[David Oxilia <oxilia@xxxxxxxxxxxx>]

As we have had mail problems due to severe rain I am forwarding
this message of yesterday. AGU is approaching; any help would
be appreciated!

thanks, David.

David Oxilia wrote:
> 
> Dear Ferreters,
> 
> One of the things I've always had trouble doing with ferret is
> masking a field to be plotted as a section (ie, lat or lon vs
> depth) by bottom topography. Say I want to plot a section of
> sigma-0. I read in my data and generate the plot. However, I
> then want to overlay a plot of the bathymetry.
> 
> How does one do this?
> 
> It is straight forward to simply draw a line plot of depth vs
> latitude say over the sigma-0 field. There is a problem though;
> that is, the line plot simply places a line over the field
> without covering up (in a uniform color) the underlying colored
> field. In essence if there was a means to do "filled curves"
> this would solve the problem. One would say something like:
> 
> yes? plot/vs/over/yfilled/nolab/line=1 lat,zb
> 
> where the yfilled would instruct to fill the curve down to the
> "y-axis" (defined by the grid) in the color specified by "line".
> Alternatively, if one could mask the field by the topography
> with something like:
> 
> yes? let masked_field = if (field_depth lt zb) then field else missing
> 
> This would allow one to contour the field with the lower bound
> masked off by the topographic height. One could then plot the
> topography line to make it stand out. This approach limits the
> topography "color" to be white though which is not entirely
> satisfactory.
> 
> Any suggestions?
> 
> David.
> 
> *~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*
> David Oxilia                    Tel: (541) 737-2368
> COAS:Oregon State University    Fax: (541) 737-2064
> Ocean Admin. Bldg. 104          WWW: http://www.oce.orst.edu/po
> Corvallis, OR 97331-5503        Email: oxilia@kundun.oce.orst.edu
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