Re: Questions about SkewT plot

Thanks for your comments Dennis. Below are my comments.

On Mon, Mar 10, 2014 at 12:30 PM, Dennis Shea <shea@ucar.edu> wrote:
>
> Hello,
>
> Please read and examine:
> http://www.ncl.ucar.edu/Applications/skewt.shtml
>
> -------
>
>
>
> http://www.ncl.ucar.edu/Applications/skewt.shtml
>
> [1] As noted in the documentation
>
> It is designed to reproduce the "USAF Skew-t, log p diagram (form dod-wpc 9-16-1).
>
> The USAF skew-t only goes to 100mb.
>
> You would have to copy the code
>
> %> $NCARG_ROOT/lib/ncarg/nclscripts/csm/skewt_func.ncl my.skewt_func.ncl
>
> and alter the code.

I need to get more familiar with your script. As this seems to require
more than a simple number change in the code.

>
>
>
> [2] See Example 1

skewtOpts@DrawColAreaFill = False ; color on background plot

setting this option to False did the trick.

>
>
> [3] CAPE calculation is somewhat sensitive to where the
> ascent is started. There are a number of CAPE codes tested
> and none agreed. There are two CAPE calculations: one by
> the WRF project and another that is included with NCL but is not
> documented.

I sent "Skew-T CAPE overestimation" titled e-mail back in Nov 2013.
There you mentioned of various CAPE calculation routines. I will yet
to compare these once I make some progress in my current research.

>
>
> [4] I think the easiest way to accomplish )say) every 5th wind would be
> to do something like
>
> uu = u
> vv = v
> uu@_Fillvalue = u@_FillValue
> uu@_Fillvalue = u@_FillValue
> uu(::5) = u(::5)
> vv(::5) = v(::5)

This assignment fails with the following message, perhaps because my u
is a 2D array.

fatal:["Execute.c":7454]:performASSIGN_VAR_VAR_OP: Number of
subscripts on rhs do not match

Jose Garcia of our department suggested a simpler way, which works perfect:

 dataOpts@Wthin = 5

To answer my original 4th question, it seems the Skew-T code needs to modified.

>
> [5] Isn't that the adibatic lapse rate!
>
> Again, you would have to modify the code.

Although I couldn't figure out to suppress the gray line, upon closer
inspection in the code, it looks like the line is the US standard
atmosphere. So, at least I have an explanation as to what it is.

>
> [6] When you open the work station
>
> wks = gsn_open_wks ("png", "skewt")

This simply does it. Thanks again.

>
> Good luck
>
> On 3/9/14, 9:19 AM, Gökhan Sever wrote:
>>
>> Hello,
>>
>> I have some questions about a Skew-T Log-P plot produced in NCL. Consider
>> the attached Weisman and Klemp (1982) type sounding as a reference, created
>> from an idealized WRF simulation output.
>>
>> 1) How to set y-axis upper limit to, say 10 mb instead of the default 100
>> mb?
>>
>> 2) How to change the green-white alternating background to white only?
>>
>> 3) The input data before calling skewT_PlotData are interpolated (using 100
>> vertical levels instead of 50) in my case, otherwise CAPE estimation seems
>> to be off by a couple hundred J/kg. However, as an artifact, there are so
>> many wind barbs are plotted. Is there a way to plot barbs, say at every 5
>> points?
>>
>> 4) How to move the barb axis or height axis so that the plot looks more
>> compact? I am only interested in u-wind, so these two axes really can be
>> combined.
>>
>> 5) What is the straight grey line ascending from in between 8-12 g/kg
>> mixing ratio lines up above? Is there a way to suppress it?
>>
>> 6) Is there a way to save SkewT plot directly to png or jpg? It's easy to
>> save in PDF, however I couldn't figure out a way to directly saving as a
>> png or jpg.
>>
>> Many thanks.
>>
>>
>>
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-- 
Gökhan
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