Re: [ferret_users] shade: a cross section with the surface topographyfilled at the bottom?

[Emilie Vanvyve <vanvyve@xxxxxxxxxxxxxx>]

Hi Mick and Jaison,

I tried all methods but couldn't implement the most rigourous ones  
since the grid of my variables doesn't match properly any of the  
solutions you suggested. The grid is x y z t with x and y = km and z  
= a sigma coordinate. Since I want to plot a cross section of the  
wind versus latitude and pressure, everything gets more complex. I  
can not regrid everything on new axis or I loose my "topography".

Therefore I use this solution: fill the graph with a uniform colour  
before plotting my variable. It works fine, is dead easy to do, but  
leads to a tiny problem that I don't understand: at the northest  
latitude, I get a "column" of grey.  I attach the graph so that you  
can see.

Here is how I plot this graph. It's extracted from a bigger script  
dealing with the time dimension or other thing, some steps here after  
might look a bit weird for that reason.

x or i = distance along a parallel, expressed in km
y or j = dimension perpendicular to x, expressed in km
z or k = vertical dimension, sigma coordinate (k=40 is the surface)

varS[x,y,z] = zonal wind
pp[y,z] = pressure averaged over 10W-10E (i=40:96@ave)
ll[y] = latitude averaged over 10W-10E (i=40:96@ave)

1. Get the background in grey:

let vv = if varS ne 0 then varS/varS else varS+1  ! vv = 1 everywhere
let vp = if k eq 40 then pp/pp*1000 else pp       ! vertical  
dimension for the background variable, I need to extend it until 1000  
hPa to get my "topography"

shade/nolabel/nokey/palette=grey/vlimit=1000:0:-100/k=7:40 vv 
[i=40:96@ave],ll,vp

2. Plot over this the zonal wind:

shade/key/pal=.../level=.../nolabel/vlimit=1000:0:-100/k=7:40/over/ 
set varS[i=40:96@ave],ll,pp
  go layout ; ppl ylab "PRESSURE (hPa)" ; ppl fill/over



I don't understand why the variable 'vv' extends much further  
northwards than the variable 'varS'. I don't do anything to this  
dimension, so both should be the same. What's going on here then?


Emilie

On 29 Sep 2006, at 20:16, Jaison Kurian wrote:

> Hi Emilie,
>            Here are 3 methods to solve your problem.
>
> Also have a look at
>
> http://www.ferret.noaa.gov/Ferret/Mail_Archives/fu_98/msg00242.html
> http://ferret.wrc.noaa.gov/Ferret/Mail_Archives/fu_2000/msg00083.html
>
> And see : ferret/examples/two_dee_plot_of_1d.jnl
>
> Plese have a trial with the example below,
>
> Hope this helps,
>
> Jaison
>
> !---------------------------------------------------------------------
> \ cancel mode verify
> !
> ! 3 methods to overlay bottom topography on vertical section plots
> !
> !-------------------------------------------------------------------
> !
> !--1. THE BEST ONE : from ferret/examples/two_dee_plot_of_1d.jnl
> !         Please note that the topography is not in the data  
> resolution
>
>    set data etopo20
>    set data levitus_climatology
>    set region/x=180:360/y=20n/z=0:5000
>    let bottom = (-1)*rose[d=etopo20]
>    let bottom_2d = bottom - z[g=temp]
>    fill temp[x=@fln:100]
>    fill/over/lev=(-10000)(0)/palette=black/nolab bottom_2d
>
>    pause
>
> !--2. Simple one, bit ugly, works good only with SHADE command.
> !        Here the topography is in the resolution of the data.
> !        Trick : define a variable which is valid where temperature
> !                 is missing, then overlay this variable.
>
>    let topo = IF temp THEN (`temp,r=bad`) ELSE 1
>    shade temp
>    shade/ov/nolab/nokey/pal=black topo
>
>    pause
>
> !--3. Better method than 2, both SHADE and FILL works fine.
> !        Here the topography is in the resolution of the data.
> !        Trick : Fill the plot area with a color (define a variable
> !                 with the same grid as temperature but with the
> !                 value 1 EVERYWHERE, use this variable to fill).
> !                 Then fill or shade temperature over this.
> !    This method will also work in one (default) view port, with
> !      "/overlay" as in 2 above. But sometime it may lead to
> !      problems with color key and "/set" & "ppl fill".
>
>    define view/xlim=0:1/ylim=0:1 v1
>    define view/xlim=0:1/ylim=0:1 v2
>    set reg/x=180:360/y=20n/z=0:5000
>    let topo = IF temp THEN 1 ELSE 1
>    set view v1
>      shade/pal=black/nolab/nokey/noaxes topo
>    set view v2
>      fill temp
> !---------------------------------------------------------------------
>
> On Fri, 29 Sep 2006, Emilie Vanvyve wrote:
>
> > Dear Ferret users,
> >
> > I looked at the online help, found some clues to help me, but I
> > haven't succeeded so far and thought of submitting my question to  
> > you.
> >
> > I plot a cross section of the zonal wind with a simple "shade/x=0/ 
> > l=1/
> > vlimit=1000:0:-100 uairdy,lat,pressure". The resulting graph is
> > joined to this email.
> > How can I get the imitation of the surface topography (the white
> > area) shaded in grey or black or whatever colour?
> >
> > In the sigma_coordinate_demo.jnl script, some similar graphs are made
> > and obviously succeeded where I fail. But the problem is taken
> > backwards: first the topography is defined (variable "bathymetry"),
> > then the variable is computed, then the variable is plotted, then the
> > bathymetry is overlayed.
> > How can I compute the surface topography from my data? I can get the
> > value of the pressure at the surface, but I haven't succeeded to make
> > it 3D "under the surface" and even less to plot it nicely.
> >
> > Would anybody know how to do?
> >
> > Many thanks in advance,
> >
> > Emilie