<div dir="ltr"><div><div><div>Hello,<br><br></div>The sample file you sent does not have the needed information. The dpres_hybrid_ccm function requires the *hybrid coefficients*.<br><br><a href="https://www.ncl.ucar.edu/Document/Functions/Built-in/dpres_hybrid_ccm.shtml">https://www.ncl.ucar.edu/Document/Functions/Built-in/dpres_hybrid_ccm.shtml</a><br><br>===<br></div>%> ncdump -h -v lev hus_6hrs_ERAI_historical_an-ml_20170301_20170302_00h.nc<br><br>dimensions:<br> lon = 480 ;<br> lat = 241 ;<br> lev = 60 ;<br> time = UNLIMITED ; // (1 currently)<br>variables:<br></div> [snip]<br><div> double lev(lev) ;<br> lev:standard_name = "hybrid_sigma_pressure" ;<br> lev:long_name = "hybrid level at layer midpoints" ;<br> lev:units = "level" ;<br> lev:positive = "down" ;<br> lev:formula = "hyam hybm (mlev=hyam+hybm*aps)" ;<br> lev:formula_terms = "ap: hyam b: hybm ps: aps" ;<br></div><div>[snip]<br> float hus(time, lev, lat, lon) ;<br></div><div>[snip]<br></div><div>lev = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, <br><div> 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, <br> 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, <br> 57, 58, 59, 60<br>----------------------<br><br></div><div>Please resend a file with the needed information.<br><br></div><div>THX<br></div><div><br><br><br></div></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Thu, Jun 22, 2017 at 4:41 PM, Ghyslaine Boschat <span dir="ltr"><<a href="mailto:ghyslaine.boschat@unimelb.edu.au" target="_blank">ghyslaine.boschat@unimelb.edu.au</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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<span style="font-family:Times" lang="EN-US">Dear NCL users,<u></u><u></u></span></p>
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<span style="font-family:Times" lang="EN-US"> </span></p>
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<span style="font-family:Times" lang="EN-US">I am using NCL version 6.4.0 to calculate vertically integrated meridional energy transports in the atmosphere using ERA-Interim. I am specifically using the NCL functions <b>cz2ccm</b> to calculate the geopotential
height in hybrid coordinates and then <b>dpres_hybrid_ccm</b> to perform vertical integration of my data on model levels.<u></u><u></u></span></p>
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<span style="font-family:Times" lang="EN-US">Both these NCL functions require as input the hybrid base pressure <b>p0 </b>and hybrid coefficients a and b. p0 is usually equal to 100000Pa but is not available for ERA-Interim and I am not sure what to use…<u></u><u></u></span></p>
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<span style="font-family:Times" lang="EN-US">To my understanding, NCL assumes the coefficients are of the form: </span><span lang="EN-US"><u></u><u></u></span></p>
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<span style="font-family:Times" lang="EN-US"> <wbr> p = a(k)*p0 + b(k)*ps </span><span lang="EN-US"><u></u><u></u></span></p>
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<span style="font-family:Times" lang="EN-US">whereas the equivalent ERA-Interim pressure equation is </span><span lang="EN-US"><u></u><u></u></span></p>
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<span style="font-family:Times" lang="EN-US"> <wbr> p = A(k) + B(k)*ps</span><span lang="EN-US"><u></u><u></u></span></p>
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<span style="font-family:Times" lang="EN-US">Therefore, for ERA-Interim data do I need to just use <b><i>p0=1</i></b> or else keep <b><i>p0 = 100000</i></b> with the provided hybrid coefficients becoming hyam= hyam/p0 and hyai= hyai/p0 (i.e. A(k)=a(k)/p0)?<u></u><u></u></span></p>
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<span style="font-family:Times" lang="EN-US">My results are slightly different depending on these 2 options.</span><span lang="EN-US"><u></u><u></u></span></p>
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<span style="font-family:Times" lang="EN-US">Thank you for your help with this.</span><span lang="EN-US"><u></u><u></u></span></p>
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<span style="font-family:Times" lang="EN-US">Regards, </span><span class="HOEnZb"><font color="#888888"><span lang="EN-US"><u></u><u></u></span></font></span></p><span class="HOEnZb"><font color="#888888">
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<span style="font-family:Times" lang="EN-US">Ghyslaine</span></p>
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