[gradsusr] Sfc level in ctl file

Sun Nov 13 21:22:43 EST 2011

Right, well since I am doing mountains I am attempting to plot this around 850 mb instead. That way, other variables will be represented near the sfc in the region of interest, and this CINsfc will also be exactly appropriate since it is just a sfc specific value. If there is little instability, I would expect instead stability and thus CIN should be pretty common year long, but I could be schooled on that. I am looking for a proxy for static stability and this is the best I can find from the ctl file. My next best bet is to somehow extract the vertical potential temp profile into column format (like in excel or something) so I can calculate N^2 myself, which is what I really want, but I also would need terrain gradient vectors to plot so that I can ultimately get the wind in the direction of the gradient and then get the Froude number from there.

Mason
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From: gradsusr-bounces at gradsusr.org [gradsusr-bounces at gradsusr.org] on behalf of Jeff Duda [jeffduda319 at gmail.com]
Sent: Sunday, November 13, 2011 8:02 PM
To: GrADS Users Forum
Subject: Re: [gradsusr] Sfc level in ctl file

It's always best to set the vertical level to the lowest you have (1000 or z = 1) when attempting to plot surface based data.  For some data files, you may get an "entire grid undefined" error if you don't.  Anyway, the reason you are getting an "all red" image is because CINSFC is some constant value.  Given that you are displaying data in the Plains and Rockies during December, where it's climatologically unlikely to see any instability, then it makes sense that there is no CIN.  Try moving your domain towards the tropics.  You shouldn't get constant 0 then.

Jeff

On Sun, Nov 13, 2011 at 6:04 PM, Rowell, Mason D. <Mason.D.Rowell-1 at ou.edu<mailto:Mason.D.Rowell-1 at ou.edu>> wrote:
Right, so since CINsfc is not specific to some level, the result should be the same CIN contouring no matter what I have lev set to in my script. Rather I set it to 1000 or 500, the contours should be exactly the same for these plots since this field is not dependent on what I set for lev, correct? At any rate, all I get is a constant red field for CIN instead of anything contoured. The attached script contours nothing at 1000 and instead gives me the red field, nor will it at any other hgt value.

Mason
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From: gradsusr-bounces at gradsusr.org<mailto:gradsusr-bounces at gradsusr.org> [gradsusr-bounces at gradsusr.org<mailto:gradsusr-bounces at gradsusr.org>] on behalf of Jeff Duda [jeffduda319 at gmail.com<mailto:jeffduda319 at gmail.com>]
Sent: Sunday, November 13, 2011 4:43 PM

To: GrADS Users Forum
Subject: Re: [gradsusr] Sfc level in ctl file

CINsfc should be the CIN of a surface based parcel using surface data, not data interpolated to 1000 mb.

On Sun, Nov 13, 2011 at 3:22 PM, Rowell, Mason D. <Mason.D.Rowell-1 at ou.edu<mailto:Mason.D.Rowell-1 at ou.edu>> wrote:
Jennifer,

Okay I think we are on the same page. My question is that if I set levs to 0, and I say plotted CINsfc, it would be the actual sfc based CIN that is plotted, and not something adjusted to sea level? That is a quantity that varies quasi-horizontally across the height varying surface itself?

Mason
________________________________
From: gradsusr-bounces at gradsusr.org<mailto:gradsusr-bounces at gradsusr.org> [gradsusr-bounces at gradsusr.org<mailto:gradsusr-bounces at gradsusr.org>] on behalf of Jennifer Adams [jma at cola.iges.org<mailto:jma at cola.iges.org>]
Sent: Sunday, November 13, 2011 11:48 AM
To: GrADS Users Forum
Subject: Re: [gradsusr] Sfc level in ctl file

In the documentation, http://iges.org/grads/gadoc/descriptorfile.html#VARS , it says:
"If levs is 0, the variable does not correspond to any vertical level. Surface variables (e.g. sea level pressure) have a levs value of 0."
If you put a "1" in the levs column, it means the variable has a Z dimension size of 1 and the value corresponds to the first value in the ZDEF statement.

--Jennifer

On Nov 13, 2011, at 12:18 PM, Rowell, Mason D. wrote:

All,

I was wondering if there were any users of the NARR data in grads that could explain something to me. Several of the variables in the ctl file are only at level 0, like this 'CINsfc          0 156,1,0 '

I recognize that those with 29 in the first column are defined on all 29 reanalysis levels, but level 0 means what? I just want to make sure that if I can set the level of the data to the sfc that it is a terrain following surface and not 1000 mb adjusted. Though it seems that 1000 is level 1, and thus level 0 is something special, like the actual surface that is not along any constant pressure sfc.

Mason
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Jennifer M. Adams
IGES/COLA
4041 Powder Mill Road, Suite 302
Calverton, MD 20705
jma at cola.iges.org<mailto:jma at cola.iges.org>

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Jeff Duda
Grad student - PhD, Meteorology
University of Oklahoma School of Meteorology - Center for Analysis and Prediction of Storms

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Jeff Duda
Grad student - PhD, Meteorology
University of Oklahoma School of Meteorology - Center for Analysis and Prediction of Storms

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