Re: Vectors on polar stereographic plots

[Ansley Manke <ansley.b.manke@xxxxxxxx>]

Hi Steven,
I don't see anything wrong with your script just from reading it,
but without the data I can't tell what might be happening.  Could you
perhaps make an example with one of the standard datasets that
comes with the Ferret distribution?

A couple of things to try, which you may of course have done

- Do a rectangular vector plot.  Do the vectors look correct?

-  In your map-projection plot, allow the default scaling of the vectors,
by leaving off the /LENGTH qualifier.

- Try the script mp_poly_vectors.  This uses a different method of
scaling and rotating the vectors.  There is a demo script, poly_vec_demo.jnl
which shows how to use this script.

Ansley Manke

Stephen Nash wrote:

> I am currently trying to produce some polar stereographic plots with 
> vectors.  I have produced the same plots in a 'normal' projection and 
> had no problems.  I have also been able to produce 'fill' plots on the 
> stereographic plots with no problems.  However, when producing vector 
> plots I only get arrows from regions where my measured field has its 
> highest values.  At some point in the code it seems that the small 
> values are being filtered out (and they're not that much smaller):
>
> set mode metafile
> use u10_2000_01_djf.cdf
> set grid u10
> let pi=4*atan(1)
> let wind=((u10^2)+(v10^2))^0.5
> let ang=atan(v10/u10)
> let dir=if u10 gt 0 then ((pi/2)-ang) else (((3*pi)/2)-ang)
> let Ts=(5.1e-4)*(wind^3)
> let Tsx=Ts*sin(dir)
> let Tsy=Ts*cos(dir)
> set window/aspect=2
> set viewport lower
> set region/x=0:360/y=-90:0/l=1:90
> go mp_stereographic_south
> !fill/levels=(0,1.5,0.1)/nolab/title="Seasonally-Averaged Integrated 
> Stokes Transport for DJF 2000/01 based on the math of McWilliams and 
> Restrepo, Southern Hemisphere" Ts[t=0:1@ave]*mp_mask, x_page, y_page
> vector/length=0.5 Tsx[t=0:1@ave]*mp_mask, 
> Tsy[t=0:1@ave]*mp_mask,x_page,y_page
> go mp_fland
> label/nouser `($PPL$XLEN)*0.5`,-0.4,0,0,.05 Seasonally-Averaged 
> Integrated Stokes Transport for DJF 2000/01 based on the math of 
> McWilliams and Restrepo, Southern Hemisphere
> set viewport upper
> set region/x=0:360/y=0:90/l=1:90
> go mp_stereographic_north
> !fill/levels=(0,1.5,0.1)/nolab/title="Seasonally-Averaged Integrated 
> Stokes Transport for DJF 2000/01 based on the math of McWilliams and 
> Restrepo, Northern Hemisphere" Ts[t=0:1@ave]*mp_mask, x_page, y_page
> vector/length=0.1 Tsx[t=0:1@ave]*mp_mask, Tsy[t=0:1@ave]*mp_mask, 
> x_page, y_page
> go mp_fland
> label/nouser `($PPL$XLEN)*0.5`,-0.4,0,0,.05 Seasonally-Averaged 
> Integrated Stokes Transport for DJF 2000/01 based on the math of 
> McWilliams and Restrepo, Northern Hemisphere
> cancel mode metafile
>
> Hope someone can help!!
>
> Thank you,
>
> Stephen Nash