<html><body><div style="color:#000; background-color:#fff; font-family:times new roman, new york, times, serif;font-size:12pt"><div id="yiv496942106"><div><div style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255); font-family: times new roman,new york,times,serif; font-size: 12pt;"><div>hi <br></div><span lang="en"><span>I</span>
 <span>am</span>
 <span>a 
student</span>
 <span>Climatology.<br></span></span><span lang="en"><span>Wanted to 
grads script calculate <span class="yiv496942106yshortcuts" id="yiv496942106lw_1354993262_0"><span class="yshortcuts" id="lw_1354993957_0">potential
 vorticity</span></span></span><span>.</span>
 <span>With</span> <span>an</span> <span>example for 20 jun 1962,level 
500hp. </span></span><span id="yiv496942106result_box" class="yiv496942106short_text" lang="en"><span class="yiv496942106hps">I
 
need</span> <span class="yiv496942106hps">to</span> <span class="yiv496942106hps">have</span> <span class="yiv496942106hps">the 
potential</span> <span class="yiv496942106hps">vorticity data.</span></span><span id="yiv496942106result_box" class="yiv496942106short_text" lang="en"><span class="yiv496942106hps">Where</span>
 <span class="yiv496942106hps">can I get</span><span class="yiv496942106">?</span></span><br><span id="yiv496942106result_box" class="yiv496942106" lang="en"><span class="yiv496942106hps">I</span> <span class="yiv496942106hps">need</span>
 </span><span id="yiv496942106result_box" class="yiv496942106" lang="en"><span class="yiv496942106hps">potential vorticity</span> <span class="yiv496942106hps">data</span></span><span id="yiv496942106result_box" class="yiv496942106" lang="en"><span class="yiv496942106hps"> for pressure</span>&nbsp;</span><span id="yiv496942106result_box" class="yiv496942106" lang="en"> <span class="yiv496942106hps"></span></span><span id="yiv496942106result_box" class="yiv496942106" lang="en"><span class="yiv496942106hps">level</span>
 <span class="yiv496942106hps"></span></span><span id="yiv496942106result_box" class="yiv496942106" lang="en"><span class="yiv496942106hps"></span><span>.</span> <span class="yiv496942106hps"><br></span></span><div style="color: rgb(0, 0, 0); font-size: 16px; font-family: times new roman,new york,times,serif; background-color: transparent; font-style: normal;"><span id="yiv496942106result_box" class="yiv496942106" lang="en"><span class="yiv496942106hps">but Site (ncep/ncar)
data</span>
 <span class="yiv496942106hps">are</span> sigma<span class="yiv496942106hps"></span> <span class="yiv496942106hps">levels</span><span class="yiv496942106">.</span></span></div><div style="color: rgb(0, 0, 0); font-size: 16px; font-family: times new roman,new york,times,serif; background-color: transparent; font-style: normal;"><span id="yiv496942106result_box" class="yiv496942106" lang="en"><span class="yiv496942106">&nbsp;&nbsp; How I can convert variables in sigma to 
pressure<br>for nc data?</span></span></div><div style="color: rgb(0, 0, 0); font-size: 16px; font-family: times new roman,new york,times,serif; background-color: transparent; font-style: normal;"><span id="yiv496942106result_box" class="yiv496942106" lang="en"><span class="yiv496942106hps">6e +06 or-5e 
+06</span> <span class="yiv496942106hps">What</span>&nbsp;<span class="yiv496942106hps"></span><span class="yiv496942106hps"></span><span class="yiv496942106hps"></span><span class="yiv496942106"></span></span><span id="yiv496942106result_box" class="yiv496942106short_text" lang="en"><span class="yiv496942106hps">Analysis</span>
 <span class="yiv496942106hps"></span></span><span id="yiv496942106result_box" class="yiv496942106" lang="en"><span class="yiv496942106hps">is</span> <span class="yiv496942106hps">the </span></span><span id="yiv496942106result_box" class="yiv496942106short_text" lang="en"><span class="yiv496942106hps">the</span> <span class="yiv496942106hps">potential



 vorticity</span> <span class="yiv496942106hps">maps</span><span class="yiv496942106">?</span></span></div><br><span lang="en"><span>Thanks
 in
 advanc<br><br>**Let me to consider an exact level for computing PV <br>**The script looks like This:<br>****** Open the zonal
 and meridional wind, temperature and it calculates Potential Vorticity 
(PV)<br>&nbsp;'reinit'<br>&nbsp;'sdfopen <a rel="nofollow" target="_blank" href="http://uwind1962jun10.nc/"><span class="yiv496942106yshortcuts" id="yiv496942106lw_1354993542_0">uwind1962jun10.nc</span></a>'<br>&nbsp;'set 
defile 1'<br>&nbsp;'define
 u = uwnd'<br>&nbsp;'sdfopen <a rel="nofollow" target="_blank" href="http://vwind1962jun10.nc/"><span class="yiv496942106yshortcuts" id="yiv496942106lw_1354993542_1">vwind1962jun10.nc</span></a>'<br>&nbsp;'set 
defile 2'<br>&nbsp;'define
 v = vwnd'<br>&nbsp;'sdfopen <a rel="nofollow" target="_blank" href="http://air1962jun10.nc/"><span class="yiv496942106yshortcuts" id="yiv496942106lw_1354993542_2">air1962jun10.nc</span></a>'<br>&nbsp;'set
 defile 3'<br>&nbsp;'define temp = air'<br>&nbsp; 'set time 10jun1962'<br>&nbsp; 'set 
lat 0 88'<br>&nbsp; 'set lon -19 120'<br>&nbsp; 'set lev 500'<br>* ########## 
Coriolis calculation<br>&nbsp; 'define coriol=2*7.29e-5*sin(lat*3.1415/180)'<br>*
 ########## Relative Vorticity calculation<br>&nbsp; 'define vort = 
hcurl(u,v)'<br>* ########## Potential Temperature (theta)calculation<br>&nbsp;
 'define 
dt=temp(z-1)*pow(1000/lev(z-1),0.286)-temp(z+1)*pow(1000/lev(z+1),0.286)'<br>&nbsp;
 'define
 dp=100*(lev(z-1)-lev(z+1))'<br>* ########## differential of 
theta/pressure<br>&nbsp; 'define dtdp=dt/dp'<br>* ########### PV calculation 
on pressure surface<br>&nbsp; 'define pv = -9.8*(coriol+vort)*dtdp'<br>&nbsp;'set 
gxout contour'<br>&nbsp;'d pv'</span></span></div></div></div>         
   </div></body></html>