<div dir="ltr">Hi Jeff.<div><br></div><div>Thanks. Fortunately I was able to use a couple of other tools to perform the calculations </div><div><br></div><div>I did try plotting the data with an arbitrary set of vertical levels. That leads to an error message stating that ZDEF is now an invalid description file record. Even though I was able to handle this elsewhere, I would still like to understand what I am doing wrong with GrADS. I have copied the dimension records from my data descriptor file below. To the ZDEF entries reflect what you mean by <span style="font-size:12.8px">plotting the data with an arbitrary set of </span><span style="font-size:12.8px">vertical levels?</span></div><div><br></div><div><div><br></div><div>XDEF lon 288 linear 0 1.25</div><div>YDEF lat 192 linear -90 0.94240837 </div><div>ZDEF 26 levels 1000 970 930 850 800 700 600 500 420 370 300 270 230 200 160 140 120 100 85 70 50 40 25 15 8 4 (arbitrary z axis values)</div><div>*ZDEF 26 levels 992.556 970.554 929.648 867.160 787.702 696.796 600.524 510.455 433.895 368.817 313.501 266.481 226.513 192.539 163.662 139.115 118.250 100.514 85.439 70.059 53.114 37.230 23.944625 13.967214 7.388 3.544 (<b>values matching the sigma-pressure levels)</b></div><div>TDEF time 840 linear 01jan2020 1mo</div><div><br></div><div>Thanks again!</div><div>Corey</div><div><br></div></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Sun, May 29, 2016 at 12:00 PM, <span dir="ltr"><<a href="mailto:gradsusr-request@gradsusr.org" target="_blank">gradsusr-request@gradsusr.org</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Send gradsusr mailing list submissions to<br>
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1. Re: Atmosphere_hybrid_sigma_pressure_coordinate (Jeff Duda)<br>
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----------------------------------------------------------------------<br>
<br>
Message: 1<br>
Date: Sun, 29 May 2016 00:16:50 -0500<br>
From: Jeff Duda <<a href="mailto:jeffduda319@gmail.com">jeffduda319@gmail.com</a>><br>
Subject: Re: [gradsusr] Atmosphere_hybrid_sigma_pressure_coordinate<br>
To: GrADS Users Forum <<a href="mailto:gradsusr@gradsusr.org">gradsusr@gradsusr.org</a>><br>
Message-ID:<br>
<<a href="mailto:CAAig09BEnghZGYfm3kKgX-JWs9xyPSHBoFk%2B9P%2BFcsXs92he4A@mail.gmail.com">CAAig09BEnghZGYfm3kKgX-JWs9xyPSHBoFk+9P+FcsXs92he4A@mail.gmail.com</a>><br>
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<br>
Have you actually tried just plotting the data with an arbitrary set of<br>
vertical levels? The values you specify for ZDEF in your control file do<br>
not have to exactly match the vertical levels of your data. What really<br>
matters is how many vertical levels there are.<br>
<br>
Now, if you want to start performing calculations such as the spatial<br>
average of Q at a specific level like 850 mb, that's a bit more tricky, but<br>
as long as you know the structure of the vertical levels, you should be<br>
able to calculate it.<br>
<br>
Jeff Duda<br>
<br>
On Thu, May 26, 2016 at 12:12 PM, Corey Gabriel <<a href="mailto:cjgabriel7@gmail.com">cjgabriel7@gmail.com</a>><br>
wrote:<br>
<br>
> Dear gradsusr community,<br>
><br>
> I am attempting to create a zonal mean plot of a variable (Q), which has<br>
> 26 levels.<br>
><br>
> The vertical coordinates are "hybrid sigma pressure." I have created a<br>
> data descriptor file and entered the vertical coordinates in the following<br>
> manner: ZDEF 26 levels L1 L2 ... L26.<br>
><br>
> I have reviewed the GrADS documentation, and it seems that several<br>
> examples suggest that the vertical coordinates should be in pure pressure<br>
> coordinates and that GrADS may not read these hybrid coordinates.<br>
><br>
> The relevant ncdump infomration is provided below. Just below the<br>
> dimensions, you can see that the formula from which the sigma coordinates<br>
> are calculated from actual pressure and surface pressure are provided.<br>
><br>
> Has anyone attempted to plot hybrid sigma pressure coordinates in GrADS<br>
> before? If so, would someone be able to provide an explanation of how to<br>
> convert the vertical coordinate into something GrADS will read?<br>
><br>
> Thanks so much!<br>
> Corey<br>
><br>
> ncdump -c <a href="http://q.corey30.001.cam.2020-01-2089-12.nc" rel="noreferrer" target="_blank">q.corey30.001.cam.2020-01-2089-12.nc</a><br>
><br>
> netcdf q.corey30.001.cam.2020-01-2089-12 {<br>
><br>
> dimensions:<br>
><br>
> lev = 26 ;<br>
><br>
> time = UNLIMITED ; // (840 currently)<br>
><br>
> lat = 192 ;<br>
><br>
> lon = 288 ;<br>
><br>
> nbnd = 2 ;<br>
><br>
> variables:<br>
><br>
> double lev(lev) ;<br>
><br>
> lev:long_name = "hybrid level at midpoints (1000*(A+B))" ;<br>
><br>
> lev:units = "level" ;<br>
><br>
> lev:positive = "down" ;<br>
><br>
> lev:standard_name = "atmosphere_hybrid_sigma_pressure_coordinate" ;<br>
><br>
> lev:formula_terms = "a: hyam b: hybm p0: P0 ps: PS" ;<br>
><br>
> double time(time) ;<br>
><br>
> time:long_name = "time" ;<br>
><br>
> time:units = "days since 2004-01-01 00:00:00" ;<br>
><br>
> time:calendar = "noleap" ;<br>
><br>
> time:bounds = "time_bnds" ;<br>
><br>
> double lat(lat) ;<br>
><br>
> lat:long_name = "latitude" ;<br>
><br>
> lat:units = "degrees_north" ;<br>
><br>
> double lon(lon) ;<br>
><br>
> lon:long_name = "longitude" ;<br>
><br>
> lon:units = "degrees_east" ;<br>
><br>
> double time_bnds(time, nbnd) ;<br>
><br>
> time_bnds:long_name = "time interval endpoints" ;<br>
><br>
> float Q(time, lev, lat, lon) ;<br>
><br>
> Q:mdims = 1 ;<br>
><br>
> Q:units = "kg/kg" ;<br>
><br>
> Q:long_name = "Specific humidity" ;<br>
><br>
> Q:cell_methods = "time: mean" ;<br>
><br>
><br>
> // global attributes:<br>
><br>
> :Conventions = "CF-1.0" ;<br>
><br>
> :source = "CAM" ;<br>
><br>
> :case = "corey30" ;<br>
><br>
> :title = "UNSET" ;<br>
><br>
> :logname = "cgabriel" ;<br>
><br>
> :host = "ys0861" ;<br>
><br>
> :Version = "$Name$" ;<br>
><br>
> :revision_Id = "$Id$" ;<br>
><br>
> :initial_file =<br>
> "/glade/p/acd/tilmes/inputdata/init/ccmi/b.e11.TSREFC2.f19.f19.ccmi23.1deg_26L.001"<br>
> ;<br>
><br>
> :topography_file = "/glade/p/cesmdata/cseg/inputdata/atm/cam/topo/<br>
> <a href="http://USGS-gtopo30_0.9x1.25_remap_c051027.nc" rel="noreferrer" target="_blank">USGS-gtopo30_0.9x1.25_remap_c051027.nc</a>"<br>
><br>
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><br>
><br>
<br>
<br>
--<br>
Jeff Duda<br>
Graduate research assistant<br>
University of Oklahoma School of Meteorology<br>
Center for Analysis and Prediction of Storms<br>
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</blockquote></div><br></div>