<div dir="ltr"><div><div><div>Jose,<br><br></div>The model sigma levels are there to distribute your model levels between the model top and the surface. Since pressure will vary at the surface, both horizontally and temporally, then the sigma value of 1 will be your surface level (versus the model top, with the sigma value of 0, which will usually be a fixed pressure). Your first model level (or any other sigma level) above the surface should have a pressure of (model top) + (sigma)*(surface pressure - model top). Thus, if you have a model top of 50 mb, a surface pressure of 1000 mb, and a first sigma value above the surface of 0.995, then the pressure of that sigma level should be 50 + 0.995 * (1000 - 50) = 995.25 mb (and from there you can calculate the height, which would be a little less than 50 meters). It should be pretty easy to get 8 or more levels below 1 km in a model, though obviously be careful to not have any sudden changes in distance between sigma levels (so something like 0.970, 0.964, 0.933 would be bad).<br><br></div>Later...<br></div>Brandt<br><br><div><div><br><br></div></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Sep 6, 2016 at 3:05 PM, Jose Augusto Paixão Veiga <span dir="ltr"><<a href="mailto:veiga.uea@gmail.com" target="_blank">veiga.uea@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"><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">Brandt,</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">based on your explanations (if I not loose anything), I can't choose the first model level, since the WRF do it during the course of run (based on the initial and boundary conditions). If it is true, why is there an option to set the model sigma levels?</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">I want to set a run (in non-hydrostatic mode) with 8 or more levels between surface and 1 km of altitude to "better resolve" PBL processes (you already show me how to do that). But, I'd like the first model level start at 50 meters of altitude. In this case, what should I do? </div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">My advanced apologises for any mistake or problem of interpretation from your explanation on this issue.</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"> </div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">Thanks</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><br></div></div><div class="gmail_extra"><span class=""><br clear="all"><div><div data-smartmail="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div><span style="font-family:arial,sans-serif;font-size:13px;border-collapse:collapse"><br></span></div><div><span style="font-family:arial,sans-serif;font-size:13px;border-collapse:collapse"><font color="#333333"><span style="background-color:rgb(255,255,255)">José Augusto P. Veiga</span></font></span></div><div><span style="font-family:arial,sans-serif;font-size:13px;border-collapse:collapse"><span style="color:rgb(51,51,51);font-family:arial;font-size:small">CREA n.: 24161</span></span></div><div><span style="border-collapse:collapse"><font color="#333333"><font size="2" face="arial"><br></font>==============================<wbr>========</font></span></div><div><span style="font-family:arial,sans-serif;font-size:13px;border-collapse:collapse"><font color="#333333">Universidade do Estado do Amazonas <br>Departamento de Meteorologia<br><span style="border-collapse:separate;font-family:arial;font-size:small">Escola Superior de Tecnologia (EST)</span></font></span><span style="font-family:arial;font-size:small;color:rgb(51,51,51)"> </span></div><div><span style="color:rgb(51,51,51)">==============================<wbr>========</span><br></div><div><span style="font-family:arial,sans-serif;font-size:13px;border-collapse:collapse"><span style="border-collapse:separate;font-family:arial;font-size:small"><font color="#333333">Av. Darcy Vargas, 1200, Manaus-AM Brasil<br>Work phone: (92) 3878 4317, Ramal 4317<br>Skype:<span style="background-color:rgb(255,255,255)"> veiga_j.a.p.</span><br></font></span></span></div><div><span style="color:rgb(51,51,51)">==============================<wbr>========</span><font color="#333333"><br>CV: <a href="http://lattes.cnpq.br/4027612512091565" target="_blank"><font style="background-color:rgb(255,255,255)" color="#333333">http://lattes.cnpq.br/<wbr>4027612512091565</font></a><br>Site: </font><a href="https://scientificmet.wordpress.com" target="_blank">https://scientificmet.<wbr>wordpress.com</a><font color="#333333"><br></font><span style="color:rgb(51,51,51)">==============================<wbr>========</span></div><div><font color="#333333"><span style="font-family:arial,sans-serif;font-size:13px;border-collapse:collapse"><br></span></font></div><div><font color="#333333"><span style="font-family:arial,sans-serif;font-size:13px;border-collapse:collapse"><br></span></font></div><div><font color="#333333"><span style="font-family:arial,sans-serif;font-size:13px;border-collapse:collapse"><br></span></font></div></div></div></div></div></div></div></div></div></div></div>
<br></span><div><div class="h5"><div class="gmail_quote">On Tue, Sep 6, 2016 at 5:21 PM, Brandt Maxwell - NOAA Federal <span dir="ltr"><<a href="mailto:brandt.maxwell@noaa.gov" target="_blank">brandt.maxwell@noaa.gov</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"><div><div><div>Jose,<br><br></div>WRF can be run either hydrostatically or (preferred) non-hydrostatically. Any pressures at the corresponding heights/pressures, including at the surface, should be determined by the WRF (based on intial and boundary conditions). Some people use an ideal/standard atmosphere experimentally as input to the WRF (perhaps they add an anomaly of some sort to specificially study the resulting effect), though this is far different from using real data, which is almost always substantially different from the standard atmosphere.<br><br></div>Later...<span><font color="#888888"><br></font></span></div><span><font color="#888888">Brandt<br><br></font></span></div><div><div><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Sep 6, 2016 at 1:04 PM, Jose Augusto Paixão Veiga <span dir="ltr"><<a href="mailto:veiga.uea@gmail.com" target="_blank">veiga.uea@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"><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">Hi Brandt Naxwell,</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">thank you very much for all your very clear explanations.</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">It seems that, considering an ideal atmosphere we can inclusively from the hydrostatic equation set the model first level. I mean ... from the equation p(z) = po exp(-z/H), where H = RT/g0, z is given in km, and po = 101300,0 Pa (atmospheric pressure at surface), we can compute a pressure value related to any height and include it in the model. Is it correct?</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"> </div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">Thank you again.</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"> </div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><br></div><div class="gmail_extra"><span><br clear="all"><div><div data-smartmail="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div><span style="font-family:arial,sans-serif;font-size:13px;border-collapse:collapse"><br></span></div><div><span style="font-family:arial,sans-serif;font-size:13px;border-collapse:collapse"><font color="#333333"><span style="background-color:rgb(255,255,255)">José Augusto P. Veiga</span></font></span></div><div><span style="font-family:arial,sans-serif;font-size:13px;border-collapse:collapse"><span style="color:rgb(51,51,51);font-family:arial;font-size:small">CREA n.: 24161</span></span></div><div><span style="border-collapse:collapse"><font color="#333333"><font size="2" face="arial"><br></font>==============================<wbr>========</font></span></div><div><span style="font-family:arial,sans-serif;font-size:13px;border-collapse:collapse"><font color="#333333">Universidade do Estado do Amazonas <br>Departamento de Meteorologia<br><span style="border-collapse:separate;font-family:arial;font-size:small">Escola Superior de Tecnologia (EST)</span></font></span><span style="font-family:arial;font-size:small;color:rgb(51,51,51)"> </span></div><div><span style="color:rgb(51,51,51)">==============================<wbr>========</span><br></div><div><span style="font-family:arial,sans-serif;font-size:13px;border-collapse:collapse"><span style="border-collapse:separate;font-family:arial;font-size:small"><font color="#333333">Av. Darcy Vargas, 1200, Manaus-AM Brasil<br>Work phone: (92) 3878 4317, Ramal 4317<br>Skype:<span style="background-color:rgb(255,255,255)"> veiga_j.a.p.</span><br></font></span></span></div><div><span style="color:rgb(51,51,51)">==============================<wbr>========</span><font color="#333333"><br>CV: <a href="http://lattes.cnpq.br/4027612512091565" target="_blank"><font style="background-color:rgb(255,255,255)" color="#333333">http://lattes.cnpq.br/40276125<wbr>12091565</font></a><br>Site: </font><a href="https://scientificmet.wordpress.com" target="_blank">https://scientificmet.wo<wbr>rdpress.com</a><font color="#333333"><br></font><span style="color:rgb(51,51,51)">==============================<wbr>========</span></div><div><font color="#333333"><span style="font-family:arial,sans-serif;font-size:13px;border-collapse:collapse"><br></span></font></div><div><font color="#333333"><span style="font-family:arial,sans-serif;font-size:13px;border-collapse:collapse"><br></span></font></div><div><font color="#333333"><span style="font-family:arial,sans-serif;font-size:13px;border-collapse:collapse"><br></span></font></div></div></div></div></div></div></div></div></div></div></div>
<br></span><div><div><div class="gmail_quote">On Tue, Sep 6, 2016 at 3:06 PM, Brandt Maxwell - NOAA Federal <span dir="ltr"><<a href="mailto:brandt.maxwell@noaa.gov" target="_blank">brandt.maxwell@noaa.gov</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"><div><div><div><div><div>Jose,<br><br></div>First of all, I think these should be sigma levels, even though they're called eta levels in WRF. The sigma levels are based on pressure, so one can calculate approximately how many levels would be below the pressure found at 1 km above the surface (though not this will vary based on surface elevation, temperature in the layer, among other things).<br><br></div>If you have a surface (for simplicity sake) of 1010 mb and a top of 10 mb (many of us will have a lower top), then 0,001 in the sigma coordinates would equate to about 1 mb. 1 km above the surface would be around 900 mb given the above surface pressure, so you can approximate anything between sigma levels of .890 and 1.000 to be below 1 km (you can use a standard atmosphere calculator to see how things like temperature can affect this). If your model top is really low, like 100 mb, then your 1 km sigma level would be more like .880.<br><br></div>Later...<br></div>Brandt Maxwell<br></div>National Weather Service/San Diego<br> <br><div><div><div><div><br><br></div></div></div></div></div><div class="gmail_extra"><br><div class="gmail_quote"><div><div>On Sun, Sep 4, 2016 at 4:03 PM, Jose Augusto Paixão Veiga <span dir="ltr"><<a href="mailto:veiga.uea@gmail.com" target="_blank">veiga.uea@gmail.com</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"><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">Dear all,</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">I am using the following eta levels in my runs with WRF (38 in this case). </div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><br></div><div class="gmail_default"><p style="font-family:'andale mono';margin:0px;font-size:13px;line-height:normal;color:rgb(195,55,32)"><b>eta_levels = 1.000, 0.995, 0.990, 0.985, 0.980, </b></p>
<p style="font-family:'andale mono';margin:0px;font-size:13px;line-height:normal;color:rgb(195,55,32)"><b> 0.970, 0.960, 0.950, 0.940, 0.930, </b></p>
<p style="font-family:'andale mono';margin:0px;font-size:13px;line-height:normal;color:rgb(195,55,32)"><b> 0.920, 0.910, 0.900, 0.880, 0.860, </b></p>
<p style="font-family:'andale mono';margin:0px;font-size:13px;line-height:normal;color:rgb(195,55,32)"><b> 0.830, 0.800, 0.770, 0.740, 0.710, </b></p>
<p style="font-family:'andale mono';margin:0px;font-size:13px;line-height:normal;color:rgb(195,55,32)"><b> 0.680, 0.640, 0.600, 0.560, 0.520, </b></p>
<p style="font-family:'andale mono';margin:0px;font-size:13px;line-height:normal;color:rgb(195,55,32)"><b> 0.480, 0.440, 0.400, 0.360, 0.320, </b></p>
<p style="font-family:'andale mono';margin:0px;font-size:13px;line-height:normal;color:rgb(195,55,32)"><b> 0.280, 0.240, 0.200, 0.160, 0.120, </b></p>
<p style="font-family:'andale mono';margin:0px;font-size:13px;line-height:normal;color:rgb(195,55,32)"><b> 0.080, 0.040, 0.000</b></p><p style="font-family:'andale mono';margin:0px;font-size:13px;line-height:normal;color:rgb(195,55,32)"><br></p><p style="font-family:'andale mono';margin:0px;font-size:13px;line-height:normal;color:rgb(195,55,32)"><br></p>However, I would like to know how many levels, in this example, are included (a) in the first km and (b) how can I identify the eta level representing the first km? </div><div class="gmail_default"><br></div><div class="gmail_default">I really appreciate any comment on this issue.</div><div class="gmail_default"><br></div><div class="gmail_default">Thanks.</div><div class="gmail_default"><br></div><div class="gmail_default"><br></div><div class="gmail_default"> <p style="font-family:'andale mono';margin:0px;font-size:13px;line-height:normal;color:rgb(195,55,32)"><br></p></div><div><div><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div><span style="font-family:arial,sans-serif;font-size:13px;border-collapse:collapse"><br></span></div><div><span style="font-family:arial,sans-serif;font-size:13px;border-collapse:collapse"><font color="#333333"><span style="background-color:rgb(255,255,255)">José Augusto P. Veiga</span></font></span></div><div><span style="font-family:arial,sans-serif;font-size:13px;border-collapse:collapse"><span style="color:rgb(51,51,51);font-family:arial;font-size:small">CREA n.: 24161</span></span></div><div><span style="border-collapse:collapse"><font color="#333333"><font size="2" face="arial"><br></font>==============================<wbr>========</font></span></div><div><span style="font-family:arial,sans-serif;font-size:13px;border-collapse:collapse"><font color="#333333">Universidade do Estado do Amazonas <br>Departamento de Meteorologia<br><span style="border-collapse:separate;font-family:arial;font-size:small">Escola Superior de Tecnologia (EST)</span></font></span><span style="font-family:arial;font-size:small;color:rgb(51,51,51)"> </span></div><div><span style="color:rgb(51,51,51)">==============================<wbr>========</span><br></div><div><span style="font-family:arial,sans-serif;font-size:13px;border-collapse:collapse"><span style="border-collapse:separate;font-family:arial;font-size:small"><font color="#333333">Av. Darcy Vargas, 1200, Manaus-AM Brasil<br>Work phone: (92) 3878 4317, Ramal 4317<br>Skype:<span style="background-color:rgb(255,255,255)"> veiga_j.a.p.</span><br></font></span></span></div><div><span style="color:rgb(51,51,51)">==============================<wbr>========</span><font color="#333333"><br>CV: <a href="http://lattes.cnpq.br/4027612512091565" target="_blank"><font style="background-color:rgb(255,255,255)" color="#333333">http://lattes.cnpq.br/40276125<wbr>12091565</font></a><br>Site: </font><a href="https://scientificmet.wordpress.com" target="_blank">https://scientificmet.wo<wbr>rdpress.com</a><font color="#333333"><br></font><span style="color:rgb(51,51,51)">==============================<wbr>========</span></div><div><font color="#333333"><span style="font-family:arial,sans-serif;font-size:13px;border-collapse:collapse"><br></span></font></div><div><font color="#333333"><span style="font-family:arial,sans-serif;font-size:13px;border-collapse:collapse"><br></span></font></div><div><font color="#333333"><span style="font-family:arial,sans-serif;font-size:13px;border-collapse:collapse"><br></span></font></div></div></div></div></div></div></div></div></div></div></div>
</div>
<br></div></div>______________________________<wbr>_________________<br>
Wrf-users mailing list<br>
<a href="mailto:Wrf-users@ucar.edu" target="_blank">Wrf-users@ucar.edu</a><br>
<a href="http://mailman.ucar.edu/mailman/listinfo/wrf-users" rel="noreferrer" target="_blank">http://mailman.ucar.edu/mailma<wbr>n/listinfo/wrf-users</a><br>
<br></blockquote></div><br></div>
</blockquote></div><br></div></div></div></div>
</blockquote></div><br></div>
</div></div></blockquote></div><br></div></div></div>
</blockquote></div><br></div>