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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><b><span style='font-size:14.0pt;color:#00B0F0'><o:p> </o:p></span></b></p><p class=MsoNormal>Good day,<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>I have managed to compute the saturation vapor pressure of two levels, say z-1 and z+1. And after computing the mixing ratios for the respective levels, I cannot seem to be able to calculate the dQs/dz (the vertical gradient of the mixing ratios). All I get whenever I attempt to compute the dQs/dz is an ERROR.<o:p></o:p></p><p class=MsoNormal>…<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>‘set z 3’<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>*At temperature t1=t(z+1)<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>‘define qs1=0.622*es1/lev’<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>*At temperature t2=t(z-1) <o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>‘define qs2=0.622*es2/lev’<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>‘define dq=(qs1-qs2)/(lev(z+1)-le(z-1))’<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>‘d dq’<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>OUTPUTS AN ERROR<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>How can I avoid the erroneous situation? Your help is highly appreciated.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Regards<o:p></o:p></p><p class=MsoNormal>Morwakoma<o:p></o:p></p><p class=MsoNormal>South African Weather Service (SAWS) Scientist<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p></div></body></html>