Re: NARR contour plots

Thank you for your help. When I try to superimpose two sets of contours
from NARR data, thickness and sea level pressure, I get the following error:

NhlAddOverlay: plot class mapPlotClass cannot be overlay plot member

I can contour thickness or pressure separately (with or without winds). But
I can¹t lay the contours on top of each other. I¹ve been told in the past
that it is not possible to overlay contours using NARR in NCL. Other people
have told me it is possible. Is it possible? I really need to know because
otherwise I will have to switch back to GEMPAK (which I don¹t want to do).

Thanks again,
Dave Small

On 3/18/09 11:36 AM, "Mary Haley" <haley_at_ucar.edu> wrote:

> Hi Dave,
>
> See example 13 at:
>
> http://www.ncl.ucar.edu/Applications/panel.shtml#ex13
>
> This isn't NARR data, but it shows how to overlay contours and vectors on a
> map.
>
> For NARR data, since you have 2D lat/lon, this example would additionally need
> the special "lon2d" and "lat2d" attributes attached to
> the data, OR, you would need to know the exact map projection that your data
> is on, and set the special "tfDoNDCOverlay" resource
> to True. See the NARR examples for how to use this special resource:
>
> http://www.ncl.ucar.edu/Applications/narr.shtml
>
> Meanwhile, if you don't have the exact map projection, and you want to use the
> 2D lat/lon coords: assumed that the data in the panel 13 example had 2D
> lat/lon coordinates called "lat" and "lon" on the file. Then, we would do
> something like this:
>
> a = addfile("uv300.nc","r")
> u = a->U(1,:,:)
> v = a->V(1,:,:)
> speed = sqrt(u^2+v^2)
> u_at_lat2d = a->lat
> u_at_lon2d = a->lon
> v_at_lat2d = u_at_lat2d
> v_at_lon2d = u_at_lon2d
> speed_at_lat2d = u_at_lat2d
> speed_at_lon2d = u_at_lon2d
> Everything else would be the same.
> For the vector plot, if you want wind barbs, set:
> vcres_at_vcGlpyhStyle = "WindBarb"
> --Mary
>
> On Mar 17, 2009, at 8:45 PM, David Small wrote:
>
>> Hello everyone,
>>
>> The NARR dataset uses 2 dimensional latitude and longitude. Is it possible
>> to lay several sets of contours over top of one another, possibly with vector
>> winds? If so, can someone tell me how to do it?
>>
>> Thank you very much.
>>
>> Dave
>>
>> --
>> David Small
>> Graduate Research Assistant
>> Department of Atmospheric and Oceanic Sciences
>> McGill University
>> Montreal, Quebec, Canada
>>
>>
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>
>

-- 
David Small
Graduate Research Assistant
Department of Atmospheric and Oceanic Sciences
McGill University
Montreal, Quebec, Canada