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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><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><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><span style='font-size:10.0pt;color:black'>Morwakoma M Matabane BSc <b>Witwatersrand</b>, H. Dipl. Comp. Sc <b>Witwatersrand</b>, BSc Hon <b>Pretoria</b>, MSc <b>Reading</b>, Research Scientist<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;color:black'>South African Weather Service 442 Rigel Avenue South Erasmusrand Pretoria 0181<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;color:black'>Tel: +27(0)12 367 6234 Fax:+27(0)12 367 6189<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;color:black'>E-mail: </span><u><span style='font-size:10.0pt;color:blue'>morwakoma.matabane@weathersa.co.za</span></u><span style='font-size:10.0pt;color:black'> Website:www.weathersa.co.za<o:p></o:p></span></p><p class=MsoNormal><img width=214 height=78 id="Picture_x0020_2" src="cid:image001.png@01CE044D.69CE1730"><span style='color:black'><o:p></o:p></span></p><p class=MsoNormal><b><i><span style='font-family:"Times New Roman","serif";color:#548DD4'> </span></i></b><b><i><span style='font-family:"Times New Roman","serif";color:blue'>“Power our future with weather, climate and water”<o:p></o:p></span></i></b></p><p class=MsoNormal><b><i><span style='font-size:9.0pt;font-family:"Times New Roman","serif";color:black'>"Big whorls have little whorls that feed on their velocity, and little whorls have lesser whorls and so on to viscosity", Lewis F Richardson.<o:p></o:p></span></i></b></p><p class=MsoNormal><b><i><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:black'><o:p> </o:p></span></i></b></p><p class=MsoNormal><b><span style='font-size:14.0pt;color:#00B0F0'><o:p> </o:p></span></b></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p></div></body></html>