<div dir="ltr">Because in areas of elevated terrain, the top of the layer in which the shear is being computed is much closer to the surface than 1 km. Said another way, they use the 900 mb level as a surrogate for the 1 km level. If the actual surface pressure is close to 900 mb, however, the vertical distance between the surface and the surrogate 1 km level is going to be quite small. Thus, the computed shear value will be expected to be lower than if you used the 1 km AGL instead.<div>
<br></div><div>Jeff</div></div><div class="gmail_extra"><br><br><div class="gmail_quote">On Sat, Sep 7, 2013 at 1:47 PM, Nimrod Micael <span dir="ltr"><<a href="mailto:nmicael@aggies.ncat.edu" target="_blank">nmicael@aggies.ncat.edu</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">@Jeff: <div><br></div><div>Ok because I find it weird that my 0-1 KM shear values at 16Z in GSO is about 1/2 of the value of the observation from a sounding taken at the time when using that shr1km(u,v) function. However, when I used Rob Hart's plotskew script to plot the sounding...the ERSH matched closer to the observation at that time. So I am wondering why such a huge error in that. </div>
</div><div class="gmail_extra"><br><br><div class="gmail_quote">On Sat, Sep 7, 2013 at 2:08 PM, Jeff Duda <span dir="ltr"><<a href="mailto:jeffduda319@gmail.com" target="_blank">jeffduda319@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">If you're calculating 0-1 km SRH over flat terrain near sea level, their computation is within reason. However, if you're on higher terrain or sloped terrain (e.g., the Plains region of the US), you'll want to use a different method.<span><font color="#888888"><div>
<br>Jeff</div></font></span></div><div><div><div class="gmail_extra"><br><br><div class="gmail_quote">On Sat, Sep 7, 2013 at 11:28 AM, Nimrod Micael <span dir="ltr"><<a href="mailto:nmicael@aggies.ncat.edu" target="_blank">nmicael@aggies.ncat.edu</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">He stated it's 1 KM MSL.<div><br></div><div><br><div><br></div><div><span style="font-family:arial,sans-serif;font-size:13px">"However, the question of AGL or MSL depends on your model data output -</span><br style="font-family:arial,sans-serif;font-size:13px">
<span style="font-family:arial,sans-serif;font-size:13px">if it compensates the pressure height. GFS IIRC does not do that, so it</span><br style="font-family:arial,sans-serif;font-size:13px"><span style="font-family:arial,sans-serif;font-size:13px">would be MSL.</span><br style="font-family:arial,sans-serif;font-size:13px">
<br style="font-family:arial,sans-serif;font-size:13px"><span style="font-family:arial,sans-serif;font-size:13px">To understand the calculation, you can check the original math from our</span><br style="font-family:arial,sans-serif;font-size:13px">
<span style="font-family:arial,sans-serif;font-size:13px">website:</span><br style="font-family:arial,sans-serif;font-size:13px"><a href="http://www.saakeskus.fi/grads-scripts/63-storm-relative-helicity-0-3km" style="font-family:arial,sans-serif;font-size:13px" target="_blank">http://www.saakeskus.fi/grads-scripts/63-storm-relative-helicity-0-3km</a>"<br>
</div></div><div><br></div><div>So in order to calculate 0-1 KM shear it has to be 0-1 KM AGL?</div><div><br></div><div><br></div><div>Thanks.</div><div><br></div><div><br></div></div><div class="gmail_extra"><br><br><div class="gmail_quote">
On Fri, Sep 6, 2013 at 1:30 PM, Jeff Duda <span dir="ltr"><<a href="mailto:jeffduda319@gmail.com" target="_blank">jeffduda319@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div dir="ltr">I don't use openGrads, so there may be some specifics I'm not aware of. uVAR and vVAR are just dummy names for the u- and v-components of the wind. The inaccuracies are probably due to the exact specifics with how the 0-1 km shear is computed in the script. One big question is how is the 1 km layer wind field being computed? Is it just 1 km MSL or 1 km AGL? Those are things you need to find out. I recommend asking the authors whose email addresses are given on the linked page.<br>
<br>Jeff<br></div><div class="gmail_extra"><br><br><div class="gmail_quote"><div><div>On Fri, Sep 6, 2013 at 12:20 PM, Nimrod Micael <span dir="ltr"><<a href="mailto:nmicael@aggies.ncat.edu" target="_blank">nmicael@aggies.ncat.edu</a>></span> wrote:<br>
</div></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div><div><div dir="ltr"><h2 style="color:rgb(147,125,0);font-size:16px;font-family:'bitstream vera sans',verdana,sans-serf">
<a name="140f9c210c615c15_140f99c64d0502a2_140f945daa5b8bb2_140f4534ed44620b_140f44d21cee3a1f_srh1km_uvar_vvar_"><strong>srh1km</strong>(<em>uVAR,vVAR</em>)</a></h2><div>What is uVAR and vVAR? I dont have those variables. </div>
<div><br></div><div><a href="http://opengrads.org/doc/udxt/saakeskus/" target="_blank">http://opengrads.org/doc/udxt/saakeskus/</a><br></div><div><br></div><div>I tried replacing uVar and vVar with u and v wind but I am getting some inaccuracies with the 0-1 KM shear. Can someone help me out?</div>
<div><br></div><div>Thanks. </div><span><font color="#888888"><div><br></div>-- <br>Nimrod Micael
</font></span></div>
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<br></blockquote></div><span><font color="#888888"><br><br clear="all"><span><font color="#888888"><br>-- <br>Jeff Duda<br>Graduate research assistant<br>University of Oklahoma School of Meteorology<br>Center for Analysis and Prediction of Storms<br>
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<br></font></span></blockquote></div><span><font color="#888888"><br><br clear="all"><div><br></div>-- <br>Nimrod Micael
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<br></blockquote></div><br><br clear="all"><span class="HOEnZb"><font color="#888888"><div><br></div>-- <br>Jeff Duda<br>Graduate research assistant<br>University of Oklahoma School of Meteorology<br>Center for Analysis and Prediction of Storms<br>
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<br></font></span></blockquote></div><span class="HOEnZb"><font color="#888888"><br><br clear="all"><div><br></div>-- <br>Nimrod Micael
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<br></blockquote></div><br><br clear="all"><div><br></div>-- <br>Jeff Duda<br>Graduate research assistant<br>University of Oklahoma School of Meteorology<br>Center for Analysis and Prediction of Storms<br>
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