<html><body><div style="color:#000; background-color:#fff; font-family:times new roman, new york, times, serif;font-size:12pt"><div><span>Dear all,</span></div><div><span>How can I calculate(determine) <span style='line-height: 115%; font-family: "Times New Roman","serif"; font-size: 13pt; mso-ascii-theme-font: major-bidi; mso-fareast-font-family: Calibri; mso-fareast-theme-font: minor-latin; mso-hansi-theme-font: major-bidi; mso-bidi-theme-font: major-bidi; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA;'>polar vortex boder <span style='line-height: 115%; font-family: "Times New Roman","serif"; font-size: 13pt; mso-ascii-theme-font: major-bidi; mso-fareast-font-family: Calibri; mso-fareast-theme-font: minor-latin; mso-hansi-theme-font: major-bidi; mso-bidi-theme-font: major-bidi; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA;'>using the potential vorticity gradient in
isentropic surface in Grads?</span></span></span></div><div><span><span style='line-height: 115%; font-family: "Times New Roman","serif"; font-size: 13pt; mso-ascii-theme-font: major-bidi; mso-fareast-font-family: Calibri; mso-fareast-theme-font: minor-latin; mso-hansi-theme-font: major-bidi; mso-bidi-theme-font: major-bidi; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA;'><span style='line-height: 115%; font-family: "Times New Roman","serif"; font-size: 13pt; mso-ascii-theme-font: major-bidi; mso-fareast-font-family: Calibri; mso-fareast-theme-font: minor-latin; mso-hansi-theme-font: major-bidi; mso-bidi-theme-font: major-bidi; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA;'>Best Regards</span></span></span></div><div><span><span style='line-height: 115%; font-family: "Times New Roman","serif"; font-size: 13pt; mso-ascii-theme-font: major-bidi; mso-fareast-font-family: Calibri;
mso-fareast-theme-font: minor-latin; mso-hansi-theme-font: major-bidi; mso-bidi-theme-font: major-bidi; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA;'><span style='line-height: 115%; font-family: "Times New Roman","serif"; font-size: 13pt; mso-ascii-theme-font: major-bidi; mso-fareast-font-family: Calibri; mso-fareast-theme-font: minor-latin; mso-hansi-theme-font: major-bidi; mso-bidi-theme-font: major-bidi; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA;'>kashki</span></span></span></div><div></div><div> </div><div>Abdolreza Kashki <var id="yui-ie-cursor"></var><br>Ph.D. Student of Climatology<br>Department of Physical Geography<br>Faculty of Planing & Geography Science <br>University of Isfahan <br>Isfahan, Iran<br>Postcode:81746-73441<br>Tel:+98(311)7933119<br>Fax:+98(311)7932257<br>Cell:+989151731453</div></div></body></html>