<table cellspacing="0" cellpadding="0" border="0" ><tr><td valign="top" style="font: inherit;"><DIV><SPAN>Dear all,</SPAN></DIV>
<DIV><SPAN>How can I calculate(determine) <SPAN style="LINE-HEIGHT: 115%; FONT-FAMILY: 'serif'; FONT-SIZE: 13pt">polar vortex boder <SPAN style="LINE-HEIGHT: 115%; FONT-FAMILY: 'serif'; FONT-SIZE: 13pt">using the potential vorticity gradient in isentropic surface in Grads?</SPAN></SPAN></SPAN></DIV>
<DIV><SPAN><SPAN style="LINE-HEIGHT: 115%; FONT-FAMILY: 'serif'; FONT-SIZE: 13pt"><SPAN style="LINE-HEIGHT: 115%; FONT-FAMILY: 'serif'; FONT-SIZE: 13pt">Best Regards</SPAN></SPAN></SPAN></DIV>
<DIV><SPAN><SPAN style="LINE-HEIGHT: 115%; FONT-FAMILY: 'serif'; FONT-SIZE: 13pt"><SPAN style="LINE-HEIGHT: 115%; FONT-FAMILY: 'serif'; FONT-SIZE: 13pt">kashki</SPAN></SPAN></SPAN></DIV><BR><BR>Abdolreza&nbsp;Kashki <BR>Ph.D. Student of Climatology<BR>Department of Physical Geography<BR>Faculty of Planing &amp; Geography Science&nbsp;<BR>University of Isfahan&nbsp; <BR>Isfahan, Iran<BR>Postcode:81746-73441<BR>Tel:+98(311)7933119<BR>Fax:+98(311)7932257<BR>Cell:+989151731453</td></tr></table>