<div dir="ltr"><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">Hi Kishore,</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">
Use the following script to calculate moisture convergence:</div><div class="gmail_default"><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:13px">***********************************************************************</div>
<div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:13px">************************************************</div>
<div class="gmail_default"><div class="gmail_default" style="font-family:arial,sans-serif;font-size:13px"><font face="arial, helvetica, sans-serif">* rh = Relative Humidity in % </font></div><div class="gmail_default" style="font-family:arial,sans-serif;font-size:13px">
<font face="arial, helvetica, sans-serif">* t = Temp at *set level in degrees Kelvin</font></div><div class="gmail_default" style="font-family:arial,sans-serif;font-size:13px"><font face="arial, helvetica, sans-serif">* tc = Temp in degrees C</font></div>
<div class="gmail_default" style="font-family:arial,sans-serif;font-size:13px">
<font face="arial, helvetica, sans-serif">* td = Dewpoint at *set level in degrees C</font></div><div class="gmail_default" style="font-family:arial,sans-serif;font-size:13px"><font face="arial, helvetica, sans-serif">* e = Vapor pressure<span style="white-space:pre-wrap"> </span></font></div>
<div class="gmail_default" style="font-family:arial,sans-serif;font-size:13px"><font face="arial, helvetica, sans-serif">* mixr = Mixing ratio</font></div><div class="gmail_default" style="font-family:arial,sans-serif;font-size:13px">
<font face="arial, helvetica, sans-serif">* u = U-wind in m/s</font></div><div class="gmail_default" style="font-family:arial,sans-serif;font-size:13px">
<font face="arial, helvetica, sans-serif">* v = V-wind in m/s</font></div><div class="gmail_default" style="font-family:arial,sans-serif;font-size:13px"><font face="arial, helvetica, sans-serif">* mconv = moisture convergence/divergence. </font></div>
<div class="gmail_default" style="font-family:arial,sans-serif;font-size:13px">
<font face="arial, helvetica, sans-serif"><br></font></div><div class="gmail_default" style="font-family:arial,sans-serif;font-size:13px"><font face="arial, helvetica, sans-serif">'tc = (t-273.16)'</font></div><div class="gmail_default" style="font-family:arial,sans-serif;font-size:13px">
<font face="arial, helvetica, sans-serif">'td = tc-((14.55+0.114*tc)*(1-0.01*rh) + pow((2.5+0.007*tc)*(1-0.01*rh),3) + (15.9+0.117*tc)*pow((1-0.01*rh),14))'</font></div>
<div class="gmail_default" style="font-family:arial,sans-serif;font-size:13px"><font face="arial, helvetica, sans-serif">'vapr = 6.112*exp((17.67*td)/(td+243.5))'</font></div><div class="gmail_default" style="font-family:arial,sans-serif;font-size:13px">
<font face="arial, helvetica, sans-serif">'e = vapr*1.001+(lev-100)/900*0.0034'</font></div>
<div class="gmail_default" style="font-family:arial,sans-serif;font-size:13px"><font face="arial, helvetica, sans-serif">'mixr = 0.62197*(e/(lev-e))*1000'</font></div><div class="gmail_default" style="font-family:arial,sans-serif;font-size:13px">
<font face="arial, helvetica, sans-serif">'mconv = (1)*hdivg(u*mixr,v*mixr)*1e4'</font></div>
<div class="gmail_default" style="font-family:arial,sans-serif;font-size:13px"><font face="arial, helvetica, sans-serif">'d mconv'</font></div><div class="gmail_default" style="font-family:arial,sans-serif;font-size:13px">
<font face="arial, helvetica, sans-serif">****************************</font></div><div class="gmail_default" style="font-family:arial,sans-serif;font-size:13px"><font face="arial, helvetica, sans-serif">**************************************************</font></div>
<div class="gmail_default"><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:13px"><span style="font-family:arial,sans-serif">I have to say that neither </span>vapor pressure, mixing ratio nor even <span style="font-family:arial,sans-serif">dewpoint temperature is needed! This is because, </span><span style="font-family:arial,sans-serif">equation</span><span style="font-family:arial,sans-serif"> (2) computes dewpoint temperature:</span></div>
<div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:13px"><span style="font-family:arial,sans-serif">That is:</span></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:13px">
'td = tc-((14.55+0.114*tc)*(1-0.01*rh)+pow((2.5+0.007*tc)*(1-0.01*rh),3)+(15.9+0.117*tc)*pow((1-0.01*rh),14))'</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:13px"> <br></div>
<div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:13px">**************************</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:13px">Therefore, you only need 4 variables to calculate moisture convergence:</div>
<div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:13px">Those are:</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:13px"><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:13px">
1- relative humidity (%)</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:13px">2- air temperature (K)</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:13px">
3- u-wind component (m/s)</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:13px">4-v-wind component (m/s)</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:13px">
*************************************************</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:13px">All you have to do is to define variables based on the equations in the script. For example:</div>
<div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:13px"><br></div><div class="gmail_default"><font face="arial, helvetica, sans-serif">define u = uwnd</font><br></div><div class="gmail_default">
<span style="font-family:arial,helvetica,sans-serif">define v = vwnd</span><font face="arial, helvetica, sans-serif"><br></font></div><div class="gmail_default"><font face="arial, helvetica, sans-serif">define t = air</font><br>
</div><div class="gmail_default"><font face="arial, helvetica, sans-serif">define rh = rhum</font><br></div><div class="gmail_default"><font face="arial, helvetica, sans-serif">**********************************************************</font></div>
<div class="gmail_default" style><font face="arial, helvetica, sans-serif">I'm attaching a "moisture convergence plot" over Iran. Based on the plot, the convergence (positive) areas shown in green color and vice versa. To verify my output, I overlaid wind streams. They are quite in a good agreement with convergence and divergence regions.</font></div>
<div class="gmail_default" style><font face="arial, helvetica, sans-serif"><br></font></div><div class="gmail_default" style><font face="arial, helvetica, sans-serif">BTW, that's a surface level. And as Davide suggested, the unit of the MC will be: </font><span style="font-family:'Times New Roman',serif;font-size:9pt;line-height:115%">(g/kg*s</span><sup style="font-family:'Times New Roman',serif;line-height:115%">-1</sup><span style="font-family:'Times New Roman',serif;font-size:9pt;line-height:115%">)</span></div>
<div class="gmail_default" style><font face="arial, helvetica, sans-serif"><br></font></div><div class="gmail_default" style><font face="arial, helvetica, sans-serif"><br></font></div><div class="gmail_default" style><font face="arial, helvetica, sans-serif">Good luck,</font></div>
<div class="gmail_default" style><font face="arial, helvetica, sans-serif">Mohsen</font></div></div><div class="gmail_default" style="font-family:arial,sans-serif;font-size:13px"><br></div></div></div></div><div class="gmail_extra">
<br clear="all"><div><div dir="ltr"><span><span style="font-size:11.0pt;line-height:115%;font-family:"Calibri","sans-serif";color:#888888"></span></span><span><span dir="RTL" style="font-size:11.0pt;line-height:115%;font-family:"Arial","sans-serif";color:#888888" lang="AR-SA"><span></span></span></span>--<div>
some are weather-wise some are otherwise!</div><div>--<br>Best Wishes, <br>(Mr.) Mohsen Soltani<br>Climatology Grad Student (M.Sc.),<br>Faculty of Geography, University of Tehran, Tehran, Iran<br>
Tel: (+98) 9119772934<br>e-mail: <a href="mailto:soltani.clima@gmail.com" target="_blank">soltani.clima@gmail.com</a><br></div></div></div>
<br><br><div class="gmail_quote">On Mon, Jun 10, 2013 at 9:59 PM, Kishore Ragi <span dir="ltr"><<a href="mailto:kishoreragi@gmail.com" target="_blank">kishoreragi@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div dir="ltr">Dear users,<div><br></div><div>I can understand how to calculate moisture convergence with specific humidity/mixing ratio but, I have relative humidity.</div><div><br></div><div>Could anybody please help me how to calculate moisture convergence with relative humidity?</div>
<div><br></div><div>Thank you in advance,</div><div><br></div><div>Sincerely,</div><div><br></div><div>Kishore</div></div><div class="HOEnZb"><div class="h5"><div class="gmail_extra"><br><br><div class="gmail_quote">On Thu, May 30, 2013 at 7:11 PM, Mohsen Soltani <span dir="ltr"><<a href="mailto:soltani.clima@gmail.com" target="_blank">soltani.clima@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><span style="font-family:arial,sans-serif;font-size:13px">Dear Davide,</span><br>
</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">
<span style="font-family:arial,sans-serif;font-size:13px"><br></span></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><span style="font-family:arial,sans-serif;font-size:13px">It sounds logical! Thank you very much for your kindness.</span></div>
<span><font color="#888888">
<div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><span style="font-family:arial,sans-serif;font-size:13px"><br></span></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">
<span style="font-family:arial,sans-serif;font-size:13px">Mohsen</span></div></font></span></div><div class="gmail_extra"><div><br clear="all"><div><div dir="ltr"><span><span style="font-size:11.0pt;line-height:115%;font-family:"Calibri","sans-serif";color:#888888"></span></span><span><span dir="RTL" style="font-size:11.0pt;line-height:115%;font-family:"Arial","sans-serif";color:#888888" lang="AR-SA"><span></span></span></span>--<div>
some are weather-wise some are otherwise!</div><div>--<br>Best Wishes, <br>(Mr.) Mohsen Soltani<br>Climatology Grad Student (M.Sc.),<br>Faculty of Geography, University of Tehran, Tehran, Iran<br>
Tel: <a href="tel:%28%2B98%29%209119772934" value="+989119772934" target="_blank">(+98) 9119772934</a><br>e-mail: <a href="mailto:soltani.clima@gmail.com" target="_blank">soltani.clima@gmail.com</a><br></div></div></div>
<br><br></div><div><div><div class="gmail_quote">On Thu, May 30, 2013 at 2:54 AM, Davide Sacchetti <span dir="ltr"><<a href="mailto:davide.sacchetti@arpal.gov.it" target="_blank">davide.sacchetti@arpal.gov.it</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">specific humidity is defined as ratio of water vapor mass (g) over air<br>
mass (kg) (units: g/kg)<br>
mixing ratio is almost the same: ratio of water vapor mass (g) over DRY<br>
air mass (kg) (units: g/kg)<br>
<br>
your divergence is like d(u*mixr)/dx, then has units of (m/s * g/kg)/m:<br>
units should be g/kg*s-1<br>
<br>
bye bye<br>
Davide<br>
<div><div><br>
On Thu, 2013-05-30 at 01:39 -0700, Mohsen Soltani wrote:<br>
> Dear GrADS Users,<br>
><br>
><br>
> I employed the following script to display the moisture convergence.<br>
> But, I don't know what is the unit of the output! Please see the<br>
> attached plot and let me know what's your opinion.<br>
><br>
><br>
> ************************************************************************<br>
> * rh = Relative Humidity in %<br>
> * t = Temp at *set level in degrees Kelvin<br>
> * tc = Temp in degrees C<br>
> * td = Dewpoint at *set level in degrees C<br>
> * e = Vapor pressure<br>
> * mixr = Mixing ratio<br>
> * u = U-wind in m/s<br>
> * v = V-wind in m/s<br>
> * mconv = moisture convergence/divergence.<br>
><br>
><br>
> 'tc = (t-273.16)'<br>
> 'td = tc-((14.55+0.114*tc)*(1-0.01*rh) + pow((2.5<br>
> +0.007*tc)*(1-0.01*rh),3) + (15.9+0.117*tc)*pow((1-0.01*rh),14))'<br>
> 'vapr = 6.112*exp((17.67*td)/(td+243.5))'<br>
> 'e = vapr*1.001+(lev-100)/900*0.0034'<br>
> 'mixr = 0.62197*(e/(lev-e))*1000'<br>
> 'mconv = (1)*hdivg(u*mixr,v*mixr)*1e4'<br>
> 'd mconv'<br>
> ********************************************************<br>
><br>
><br>
><br>
><br>
> Thank you,<br>
> Mohsen<br>
><br>
><br>
> --<br>
> some are weather-wise some are otherwise!<br>
> --<br>
> Best Wishes,<br>
> (Mr.) Mohsen Soltani<br>
> Climatology Grad Student (M.Sc.),<br>
> Faculty of Geography, University of Tehran, Tehran, Iran<br>
> Tel: <a href="tel:%28%2B98%29%209119772934" value="+989119772934" target="_blank">(+98) 9119772934</a><br>
> e-mail: <a href="mailto:soltani.clima@gmail.com" target="_blank">soltani.clima@gmail.com</a><br>
><br>
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--> Attenzione cambio indirizzo: <a href="mailto:davide.sacchetti@arpal.gov.it" target="_blank">davide.sacchetti@arpal.gov.it</a><br>
--<br>
Davide Sacchetti<br>
Centro Funzionale Meteo Idrologico di Protezione Civile della Regione Liguria<br>
ARPAL Unità Tecnica Complessa di livello Regionale<br>
V.le Brigare Partigiane 2 16121 Genova (I)<br>
tel: <a href="tel:%2B39%20010%206437535" value="+390106437535" target="_blank">+39 010 6437535</a> fax: <a href="tel:%2B39%20010%206437520" value="+390106437520" target="_blank">+39 010 6437520</a><br>
mail: <a href="mailto:davide.sacchetti@arpal.gov.it" target="_blank">davide.sacchetti@arpal.gov.it</a> web: <a href="http://www.meteoliguria.it" target="_blank">www.meteoliguria.it</a><br>
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