2011/9/16 Hyacinth Nnamchi <span dir="ltr"><<a href="mailto:hyacinth.1@hotmail.com">hyacinth.1@hotmail.com</a>></span><br><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
<div><div dir="ltr">
Jeff,<br><br>I seems my question wasn't well framed, and so you dealt with the typo. I have attached two Figs showing what the calculations below will give and what exactly I'll like to do.<br><br></div></div></blockquote>
<div><br></div><div>From the attached plot it appears that you want to plot the divergent component of the mass flux, as given by the Helmholtz decomposition:</div><div><br></div><div> <a href="http://en.wikipedia.org/wiki/Helmholtz_decomposition">http://en.wikipedia.org/wiki/Helmholtz_decomposition</a></div>
<div><br></div><div>The first step is to compute the velocity potential</div><div><br></div><div> ga-> chi = fish_chi(zon,mer)</div><div><br></div><div>(As Roger mentions, make sure to average in the vertical first if this is what you want.) Next, the divergent component of the mass flux is related to the gradient of chi; see this for more information:</div>
<div><br></div><div> <a href="http://opengrads.org/doc/udxt/fish/fish.html#calculating_the_divergent_wind" style="color: rgb(119, 0, 0); font-family: monospace; white-space: pre; font-size: 14px; ">Calculating the Divergent Wind</a></div>
<div><span class="Apple-style-span" style="font-family: 'bitstream vera sans', verdana, sans-serf; font-size: 14px; "><pre>Notice that you will need an opengrads build in order to use the fish extension; more info here:</pre>
</span><span class="Apple-style-span" style="font-family: 'bitstream vera sans', verdana, sans-serf; font-size: 14px; "><pre> <a href="http://opengrads.org/wiki/index.php?title=Installing_the_OpenGrADS_Bundle">http://opengrads.org/wiki/index.php?title=Installing_the_OpenGrADS_Bundle</a></pre>
</span><span class="Apple-style-span" style="font-family: 'bitstream vera sans', verdana, sans-serf; font-size: 14px; "><pre> Good luck,</pre></span><span class="Apple-style-span" style="font-family: 'bitstream vera sans', verdana, sans-serf; font-size: 14px; "><pre style="color: rgb(119, 0, 0); ">
Arlindo</pre></span><span class="Apple-style-span" style="font-family: 'bitstream vera sans', verdana, sans-serf; font-size: 14px; "><pre style="color: rgb(119, 0, 0); "><br></pre></span><span class="Apple-style-span" style="font-family: 'bitstream vera sans', verdana, sans-serf; font-size: 14px; "><pre style="color: rgb(119, 0, 0); ">
<br></pre></span></div><div><br></div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;"><div><div dir="ltr">Thanks,<br><br>Hyacinth<br><br><br>> Date: Thu, 15 Sep 2011 17:34:50 -0500><br>
From: Jeffrey Duda <<a href="mailto:jdduda@iastate.edu" target="_blank">jdduda@iastate.edu</a>>><br> Subject: Re: [gradsusr] Moisture flux convergence/divergence<br>> To: GrADS Users Forum <<a href="mailto:gradsusr@gradsusr.org" target="_blank">gradsusr@gradsusr.org</a>><br>
<div>> Message-ID:<br>> <CAP9LQ-VNkxcu-+ey_QkZU7f4MHf+VwJDvav=<a href="mailto:Dci3ns%2Bx%2BpjG8Q@mail.gmail.com" target="_blank">Dci3ns+x+pjG8Q@mail.gmail.com</a>><br>> Content-Type: text/plain; charset="iso-8859-1"<div class="im">
<br>> <br>> Set the graphics output to vector ('set gxout vector'), then 'd zon;mer'<br>> (note the semicolon instead of a comma).<br>> <br>> Jeff Duda<br>> <br>> 2011/9/15 Hyacinth Nnamchi <<a href="mailto:hyacinth.1@hotmail.com" target="_blank">hyacinth.1@hotmail.com</a>><br>
> <br>> > Hello,<br>> ><br>> > This is not directly about GrADS but since most of address similar!
<br>> > problems, I guess someone on this forum will be able to answer my question.<br>> ><br>> > I understand that to calculate moisture transport, given zonal, meridional<br>> > winds and specific humidity, can simply do:<br>
> ><br>> > 'define zon=uwnd.1*shum.3'<br>> > 'define mer=vwnd.2*shum.3'<br>> > 'd zon,mer'<br>> ><br>> > But, I want to plot vectors indicating field of net moisture flux (all arrows converging/diverging) instead of just transport.<br>
> ><br>> > Thanks for any ideas.<br>> ><br>> > Hyacinth<br>> ><br>> ><br>> > __<br></div></div> </div></div>
<br>_______________________________________________<br>
gradsusr mailing list<br>
<a href="mailto:gradsusr@gradsusr.org">gradsusr@gradsusr.org</a><br>
<a href="http://gradsusr.org/mailman/listinfo/gradsusr" target="_blank">http://gradsusr.org/mailman/listinfo/gradsusr</a><br>
<br></blockquote></div><br><br clear="all"><div><br></div>-- <br>Arlindo da Silva<br><a href="mailto:dasilva@alum.mit.edu">dasilva@alum.mit.edu</a><br>