<html><body><div style="color:#000; background-color:#fff; 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="yiv261381422yshortcuts" id="yiv261381422lw_1354993262_0">potential
vorticity</span></span><span>.</span>
<span>With</span> <span>an</span> <span>example for 20 jun 1962,level
500hp. </span></span><span id="yiv261381422result_box" class="yiv261381422short_text" lang="en"><span class="yiv261381422hps">I
need</span> <span class="yiv261381422hps">to</span> <span class="yiv261381422hps">have</span> <span class="yiv261381422hps">the
potential</span> <span class="yiv261381422hps">vorticity data.</span></span><span id="yiv261381422result_box" class="yiv261381422short_text" lang="en"><span class="yiv261381422hps">Where</span>
<span class="yiv261381422hps">can I get</span><span class="yiv261381422">?</span></span><br><span id="yiv261381422result_box" class="yiv261381422" lang="en"><span class="yiv261381422hps">I</span> <span class="yiv261381422hps">need</span>
</span><span id="yiv261381422result_box" class="yiv261381422" lang="en"><span class="yiv261381422hps">potential vorticity</span> <span class="yiv261381422hps">data</span></span><span id="yiv261381422result_box" class="yiv261381422" lang="en"><span class="yiv261381422hps"> for pressure</span> </span><span id="yiv261381422result_box" class="yiv261381422" lang="en"> <span class="yiv261381422hps"></span></span><span id="yiv261381422result_box" class="yiv261381422" lang="en"><span class="yiv261381422hps">level</span>
<span class="yiv261381422hps"></span></span><span id="yiv261381422result_box" class="yiv261381422" lang="en"><span class="yiv261381422hps"></span><span>.</span> <span class="yiv261381422hps"><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="yiv261381422result_box" class="yiv261381422" lang="en"><span class="yiv261381422hps">but Site (ncep/ncar)
data</span>
<span class="yiv261381422hps">are</span> sigma<span class="yiv261381422hps"></span> <span class="yiv261381422hps">levels</span><span class="yiv261381422">.</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="yiv261381422result_box" class="yiv261381422" lang="en"><span class="yiv261381422"> 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="yiv261381422result_box" class="yiv261381422" lang="en"><span class="yiv261381422hps">6e +06 or-5e
+06</span> <span class="yiv261381422hps">What</span> <span class="yiv261381422hps"></span><span class="yiv261381422hps"></span><span class="yiv261381422hps"></span><span class="yiv261381422"></span></span><span id="yiv261381422result_box" class="yiv261381422short_text" lang="en"><span class="yiv261381422hps">Analysis</span>
<span class="yiv261381422hps"></span></span><span id="yiv261381422result_box" class="yiv261381422" lang="en"><span class="yiv261381422hps">is</span> <span class="yiv261381422hps">the </span></span><span id="yiv261381422result_box" class="yiv261381422short_text" lang="en"><span class="yiv261381422hps">the</span> <span class="yiv261381422hps">potential
vorticity</span> <span class="yiv261381422hps">maps</span><span class="yiv261381422">?</span></span></div><br><span lang="en"><span>Thanks
in
advanc<br><br>**Let me to consider an exact level for computing PV
(e.g. 200 hPa)<br>**The script looks like This:<br>****** Open the zonal
and meridional wind, temperature and it calculates Potential Vorticity
(PV)<br> 'reinit'<br> 'sdfopen <a target="_blank" href="http://uwind1962jun10.nc/"><span class="yshortcuts" id="lw_1354993542_0">uwind1962jun10.nc</span></a>'<br> 'set defile 1'<br> 'define
u = uwnd'<br> 'sdfopen <a target="_blank" href="http://vwind1962jun10.nc/"><span class="yshortcuts" id="lw_1354993542_1">vwind1962jun10.nc</span></a>'<br> 'set defile 2'<br> 'define
v = vwnd'<br> 'sdfopen <a target="_blank" href="http://air1962jun10.nc/"><span class="yshortcuts" id="lw_1354993542_2">air1962jun10.nc</span></a>'<br> 'set
defile 3'<br> 'define temp = air'<br> 'set time 10jun1962'<br> 'set
lat 0 88'<br> 'set lon -19 120'<br> 'set lev 500'<br>* ##########
Coriolis calculation<br> 'define coriol=2*7.29e-5*sin(lat*3.1415/180)'<br>*
########## Relative Vorticity calculation<br> 'define vort =
hcurl(u,v)'<br>* ########## Potential Temperature (theta)calculation<br>
'define
dt=temp(z-1)*pow(1000/lev(z-1),0.286)-temp(z+1)*pow(1000/lev(z+1),0.286)'<br>
'define
dp=100*(lev(z-1)-lev(z+1))'<br>* ########## differential of
theta/pressure<br> 'define dtdp=dt/dp'<br>* ########### PV calculation
on pressure surface<br> 'define pv = -9.8*(coriol+vort)*dtdp'<br> 'set
gxout contour'<br> 'd pv'</span></span></div></body></html>