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<span lang="EN-US" style="font-family: Times;">Dear NCL users,<o:p></o:p></span></p>
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<span lang="EN-US" style="font-family: Times;"> </span></p>
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<span lang="EN-US" style="font-family: Times;">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.<o:p></o:p></span></p>
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<span lang="EN-US"> </span></p>
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<span lang="EN-US" style="font-family: Times;">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…<o:p></o:p></span></p>
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<span lang="EN-US"> </span></p>
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<span lang="EN-US" style="font-family: Times;">To my understanding, NCL assumes the coefficients are of the form: </span><span lang="EN-US"><o:p></o:p></span></p>
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<span lang="EN-US" style="font-family: Times;"> p = a(k)*p0 + b(k)*ps </span><span lang="EN-US"><o:p></o:p></span></p>
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<span lang="EN-US" style="font-family: Times;">whereas the equivalent ERA-Interim pressure equation is </span><span lang="EN-US"><o:p></o:p></span></p>
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<span lang="EN-US" style="font-family: Times;"> p = A(k) + B(k)*ps</span><span lang="EN-US"><o:p></o:p></span></p>
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<span lang="EN-US" style="font-family: Times;"> </span></p>
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<span lang="EN-US" style="font-family: Times;">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)?<o:p></o:p></span></p>
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<span lang="EN-US"> </span></p>
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<span lang="EN-US" style="font-family: Times;">My results are slightly different depending on these 2 options.</span><span lang="EN-US"><o:p></o:p></span></p>
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<span lang="EN-US" style="font-family: Times;"> </span></p>
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<span lang="EN-US" style="font-family: Times;">Thank you for your help with this.</span><span lang="EN-US"><o:p></o:p></span></p>
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<span lang="EN-US"> </span></p>
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<span lang="EN-US" style="font-family: Times;">Regards, </span><span lang="EN-US"><o:p></o:p></span></p>
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<span lang="EN-US" style="font-family: Times;"><br>
</span></p>
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<span lang="EN-US" style="font-family: Times;">Ghyslaine</span></p>
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