On Wed, Sep 21, 2011 at 12:00 AM, saeed bayat <span dir="ltr"><<a href="mailto:saeedbayat7276@gmail.com">saeedbayat7276@gmail.com</a>></span> wrote:<br><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
Hi Arlindo,<br>I am working with <br><b><font size="2">Grid Analysis and Display System (GrADS) Version 2.0.a9.oga.1<br>Copyright (c) 1988-2010 by Brian Doty and the<br>Institute for Global Environment and Society (IGES)<br>
GrADS comes with ABSOLUTELY NO WARRANTY<br>See file COPYRIGHT for more information<br><br>Config: v2.0.a9.oga.1 little-endian readline printim grib2 netcdf hdf4-sds hdf5 opendap-grids,stn athena geotiff shapefile<br></font></b><br>
I check the link you mentioned above, but I am confused that what am I type <br>instead of expression exist there. I am working with output data of RegCM4.1<br>and I do not know what exactly is the PSI, CHI, FISH_CHI and some another.<br>
<br></blockquote><div><br></div><div>I am not sure I really understand what you are asking. If you enter:</div><div><br></div><div>ga-> q udf</div><div><br></div><div>you get a list of all the opengrads extension functions. Of relevance here is the *fish* package which is documented here:</div>
<div><br></div><div>� � � � �<a href="http://opengrads.org/doc/udxt/fish/">http://opengrads.org/doc/udxt/fish/</a></div><div><br></div><div>Now, it is assumed that you know (from vector calculus or from your dynamic meteorology classes) the definition of streamfunction (usually denoted psi) and velocity potential (usually denoted chi). �Given the (u,v) components of a horizontal vector (winds, mass flux, etc.) you can compute psi, chi with</div>
<div><br></div><div>ga-> psi = fish_psi(u,v)</div><div>ga-> chi = fish_chi(u,v)</div><div>��</div><div>� I hope this helps. If you are not familiar with the stream function/velocity potential concepts, work on that first, then come back to try the software.</div>
<div><br></div><div>� � �Arlindo</div><div><br></div></div><div><br></div>-- <br>Arlindo da Silva<br><a href="mailto:dasilva@alum.mit.edu">dasilva@alum.mit.edu</a><br>