<div dir="ltr">Jose,<div><br></div><div><span style="font-size:12.8px">I calculate the </span><span style="font-size:12.8px">sigma levels </span><span style="font-size:12.8px">heights (m) using the </span><span style="font-size:12.8px">wrfout variables of perturbation geopotential (PH) and base-state geopotential, </span><span lang="en" style="font-size:12.8px">through the equation (</span><span style="font-size:12.8px">(PH+PHB) / 9,8). The result gives the heights above the sea level. To calculate the heights above the ground, I subtracted the first level height from the </span><span style="font-size:12.8px">above</span><span style="font-size:12.8px"> levels heights.</span></div><div><span style="font-size:12.8px"><br></span></div><div><span style="font-size:12.8px"><br></span></div><div><span style="font-size:12.8px">Best regards,</span><br></div><div><span style="font-size:12.8px"><br></span></div><div><font size="1">Ian Dragaud</font></div><div><span style="font-family:'Helvetica Neue-Light','Helvetica Neue Light','Helvetica Neue',Helvetica,Arial,'Lucida Grande',sans-serif"><font size="1">Federal University of Rio de Janeiro</font></span><br></div><div><span style="font-size:12.8px"><br></span></div></div><div class="gmail_extra"><br><div class="gmail_quote">2016-09-06 20:21 GMT-03:00 <span dir="ltr"><<a href="mailto:wrf-users-request@ucar.edu" target="_blank">wrf-users-request@ucar.edu</a>></span>:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Send Wrf-users mailing list submissions to<br>
<a href="mailto:wrf-users@ucar.edu">wrf-users@ucar.edu</a><br>
<br>
To subscribe or unsubscribe via the World Wide Web, visit<br>
<a href="http://mailman.ucar.edu/mailman/listinfo/wrf-users" rel="noreferrer" target="_blank">http://mailman.ucar.edu/<wbr>mailman/listinfo/wrf-users</a><br>
or, via email, send a message with subject or body 'help' to<br>
<a href="mailto:wrf-users-request@ucar.edu">wrf-users-request@ucar.edu</a><br>
<br>
You can reach the person managing the list at<br>
<a href="mailto:wrf-users-owner@ucar.edu">wrf-users-owner@ucar.edu</a><br>
<br>
When replying, please edit your Subject line so it is more specific<br>
than "Re: Contents of Wrf-users digest..."<br>
<br>
<br>
Today's Topics:<br>
<br>
1. Re: Question about levels in wrf (Brandt Maxwell - NOAA Federal)<br>
<br>
<br>
------------------------------<wbr>------------------------------<wbr>----------<br>
<br>
Message: 1<br>
Date: Tue, 6 Sep 2016 16:12:09 -0700<br>
From: Brandt Maxwell - NOAA Federal <<a href="mailto:brandt.maxwell@noaa.gov">brandt.maxwell@noaa.gov</a>><br>
Subject: Re: [Wrf-users] Question about levels in wrf<br>
To: Jose Augusto Paix?o Veiga <<a href="mailto:veiga.uea@gmail.com">veiga.uea@gmail.com</a>><br>
Cc: "<a href="mailto:wrf-users@ucar.edu">wrf-users@ucar.edu</a>" <<a href="mailto:wrf-users@ucar.edu">wrf-users@ucar.edu</a>><br>
Message-ID:<br>
<<a href="mailto:CAAwUs94aEOoQm6M7b%2BLQpxrusLqNQuj3iE9DEYKas1XdnKE4iw@mail.gmail.com">CAAwUs94aEOoQm6M7b+<wbr>LQpxrusLqNQuj3iE9DEYKas1XdnKE4<wbr>iw@mail.gmail.com</a>><br>
Content-Type: text/plain; charset="utf-8"<br>
<br>
Jose,<br>
<br>
The model sigma levels are there to distribute your model levels between<br>
the model top and the surface. Since pressure will vary at the surface,<br>
both horizontally and temporally, then the sigma value of 1 will be your<br>
surface level (versus the model top, with the sigma value of 0, which will<br>
usually be a fixed pressure). Your first model level (or any other sigma<br>
level) above the surface should have a pressure of (model top) +<br>
(sigma)*(surface pressure - model top). Thus, if you have a model top of<br>
50 mb, a surface pressure of 1000 mb, and a first sigma value above the<br>
surface of 0.995, then the pressure of that sigma level should be 50 +<br>
0.995 * (1000 - 50) = 995.25 mb (and from there you can calculate the<br>
height, which would be a little less than 50 meters). It should be pretty<br>
easy to get 8 or more levels below 1 km in a model, though obviously be<br>
careful to not have any sudden changes in distance between sigma levels (so<br>
something like 0.970, 0.964, 0.933 would be bad).<br>
<br>
Later...<br>
Brandt<br>
<br>
<br>
<br>
<br>
On Tue, Sep 6, 2016 at 3:05 PM, Jose Augusto Paix?o Veiga <<br>
<a href="mailto:veiga.uea@gmail.com">veiga.uea@gmail.com</a>> wrote:<br>
<br>
> Brandt,<br>
><br>
> based on your explanations (if I not loose anything), I can't choose the<br>
> first model level, since the WRF do it during the course of run (based on<br>
> the initial and boundary conditions). If it is true, why is there an option<br>
> to set the model sigma levels?<br>
><br>
> I want to set a run (in non-hydrostatic mode) with 8 or more levels<br>
> between surface and 1 km of altitude to "better resolve" PBL processes (you<br>
> already show me how to do that). But, I'd like the first model level start<br>
> at 50 meters of altitude. In this case, what should I do?<br>
><br>
> My advanced apologises for any mistake or problem of interpretation from<br>
> your explanation on this issue.<br>
><br>
> Thanks<br>
><br>
><br>
><br>
> Jos? Augusto P. Veiga<br>
> CREA n.: 24161<br>
><br>
> ==============================<wbr>========<br>
> Universidade do Estado do Amazonas<br>
> Departamento de Meteorologia<br>
> Escola Superior de Tecnologia (EST)<br>
> ==============================<wbr>========<br>
> Av. Darcy Vargas, 1200, Manaus-AM Brasil<br>
> Work phone: (92) 3878 4317, Ramal 4317<br>
> Skype: veiga_j.a.p.<br>
> ==============================<wbr>========<br>
> CV: <a href="http://lattes.cnpq.br/4027612512091565" rel="noreferrer" target="_blank">http://lattes.cnpq.br/<wbr>4027612512091565</a><br>
> Site: <a href="https://scientificmet.wordpress.com" rel="noreferrer" target="_blank">https://scientificmet.<wbr>wordpress.com</a><br>
> ==============================<wbr>========<br>
><br>
><br>
><br>
><br>
> On Tue, Sep 6, 2016 at 5:21 PM, Brandt Maxwell - NOAA Federal <<br>
> <a href="mailto:brandt.maxwell@noaa.gov">brandt.maxwell@noaa.gov</a>> wrote:<br>
><br>
>> Jose,<br>
>><br>
>> WRF can be run either hydrostatically or (preferred)<br>
>> non-hydrostatically. Any pressures at the corresponding heights/pressures,<br>
>> including at the surface, should be determined by the WRF (based on intial<br>
>> and boundary conditions). Some people use an ideal/standard atmosphere<br>
>> experimentally as input to the WRF (perhaps they add an anomaly of some<br>
>> sort to specificially study the resulting effect), though this is far<br>
>> different from using real data, which is almost always substantially<br>
>> different from the standard atmosphere.<br>
>><br>
>> Later...<br>
>> Brandt<br>
>><br>
>><br>
>> On Tue, Sep 6, 2016 at 1:04 PM, Jose Augusto Paix?o Veiga <<br>
>> <a href="mailto:veiga.uea@gmail.com">veiga.uea@gmail.com</a>> wrote:<br>
>><br>
>>> Hi Brandt Naxwell,<br>
>>><br>
>>> thank you very much for all your very clear explanations.<br>
>>><br>
>>> It seems that, considering an ideal atmosphere we can inclusively from<br>
>>> the hydrostatic equation set the model first level. I mean ... from the<br>
>>> equation p(z) = po exp(-z/H), where H = RT/g0, z is given in km, and po =<br>
>>> 101300,0 Pa (atmospheric pressure at surface), we can compute a pressure<br>
>>> value related to any height and include it in the model. Is it correct?<br>
>>><br>
>>><br>
>>> Thank you again.<br>
>>><br>
>>><br>
>>><br>
>>><br>
>>><br>
>>><br>
>>><br>
>>><br>
>>><br>
>>><br>
>>> Jos? Augusto P. Veiga<br>
>>> CREA n.: 24161<br>
>>><br>
>>> ==============================<wbr>========<br>
>>> Universidade do Estado do Amazonas<br>
>>> Departamento de Meteorologia<br>
>>> Escola Superior de Tecnologia (EST)<br>
>>> ==============================<wbr>========<br>
>>> Av. Darcy Vargas, 1200, Manaus-AM Brasil<br>
>>> Work phone: (92) 3878 4317, Ramal 4317<br>
>>> Skype: veiga_j.a.p.<br>
>>> ==============================<wbr>========<br>
>>> CV: <a href="http://lattes.cnpq.br/4027612512091565" rel="noreferrer" target="_blank">http://lattes.cnpq.br/<wbr>4027612512091565</a><br>
>>> Site: <a href="https://scientificmet.wordpress.com" rel="noreferrer" target="_blank">https://scientificmet.<wbr>wordpress.com</a><br>
>>> ==============================<wbr>========<br>
>>><br>
>>><br>
>>><br>
>>><br>
>>> On Tue, Sep 6, 2016 at 3:06 PM, Brandt Maxwell - NOAA Federal <<br>
>>> <a href="mailto:brandt.maxwell@noaa.gov">brandt.maxwell@noaa.gov</a>> wrote:<br>
>>><br>
>>>> Jose,<br>
>>>><br>
>>>> First of all, I think these should be sigma levels, even though they're<br>
>>>> called eta levels in WRF. The sigma levels are based on pressure, so one<br>
>>>> can calculate approximately how many levels would be below the pressure<br>
>>>> found at 1 km above the surface (though not this will vary based on surface<br>
>>>> elevation, temperature in the layer, among other things).<br>
>>>><br>
>>>> If you have a surface (for simplicity sake) of 1010 mb and a top of 10<br>
>>>> mb (many of us will have a lower top), then 0,001 in the sigma coordinates<br>
>>>> would equate to about 1 mb. 1 km above the surface would be around 900 mb<br>
>>>> given the above surface pressure, so you can approximate anything between<br>
>>>> sigma levels of .890 and 1.000 to be below 1 km (you can use a standard<br>
>>>> atmosphere calculator to see how things like temperature can affect this).<br>
>>>> If your model top is really low, like 100 mb, then your 1 km sigma level<br>
>>>> would be more like .880.<br>
>>>><br>
>>>> Later...<br>
>>>> Brandt Maxwell<br>
>>>> National Weather Service/San Diego<br>
>>>><br>
>>>><br>
>>>><br>
>>>><br>
>>>> On Sun, Sep 4, 2016 at 4:03 PM, Jose Augusto Paix?o Veiga <<br>
>>>> <a href="mailto:veiga.uea@gmail.com">veiga.uea@gmail.com</a>> wrote:<br>
>>>><br>
>>>>> Dear all,<br>
>>>>><br>
>>>>> I am using the following eta levels in my runs with WRF (38 in this<br>
>>>>> case).<br>
>>>>><br>
>>>>><br>
>>>>><br>
>>>>> *eta_levels = 1.000, 0.995, 0.990, 0.985,<br>
>>>>> 0.980, *<br>
>>>>><br>
>>>>> * 0.970, 0.960, 0.950, 0.940,<br>
>>>>> 0.930, *<br>
>>>>><br>
>>>>> * 0.920, 0.910, 0.900, 0.880,<br>
>>>>> 0.860, *<br>
>>>>><br>
>>>>> * 0.830, 0.800, 0.770, 0.740,<br>
>>>>> 0.710, *<br>
>>>>><br>
>>>>> * 0.680, 0.640, 0.600, 0.560,<br>
>>>>> 0.520, *<br>
>>>>><br>
>>>>> * 0.480, 0.440, 0.400, 0.360,<br>
>>>>> 0.320, *<br>
>>>>><br>
>>>>> * 0.280, 0.240, 0.200, 0.160,<br>
>>>>> 0.120, *<br>
>>>>><br>
>>>>> * 0.080, 0.040, 0.000*<br>
>>>>><br>
>>>>><br>
>>>>><br>
>>>>> However, I would like to know how many levels, in this example, are<br>
>>>>> included (a) in the first km and (b) how can I identify the eta level<br>
>>>>> representing the first km?<br>
>>>>><br>
>>>>> I really appreciate any comment on this issue.<br>
>>>>><br>
>>>>> Thanks.<br>
>>>>><br>
>>>>><br>
>>>>><br>
>>>>><br>
>>>>><br>
>>>>><br>
>>>>> Jos? Augusto P. Veiga<br>
>>>>> CREA n.: 24161<br>
>>>>><br>
>>>>> ==============================<wbr>========<br>
>>>>> Universidade do Estado do Amazonas<br>
>>>>> Departamento de Meteorologia<br>
>>>>> Escola Superior de Tecnologia (EST)<br>
>>>>> ==============================<wbr>========<br>
>>>>> Av. Darcy Vargas, 1200, Manaus-AM Brasil<br>
>>>>> Work phone: (92) 3878 4317, Ramal 4317<br>
>>>>> Skype: veiga_j.a.p.<br>
>>>>> ==============================<wbr>========<br>
>>>>> CV: <a href="http://lattes.cnpq.br/4027612512091565" rel="noreferrer" target="_blank">http://lattes.cnpq.br/<wbr>4027612512091565</a><br>
>>>>> Site: <a href="https://scientificmet.wordpress.com" rel="noreferrer" target="_blank">https://scientificmet.<wbr>wordpress.com</a><br>
>>>>> ==============================<wbr>========<br>
>>>>><br>
>>>>><br>
>>>>><br>
>>>>><br>
>>>>> ______________________________<wbr>_________________<br>
>>>>> Wrf-users mailing list<br>
>>>>> <a href="mailto:Wrf-users@ucar.edu">Wrf-users@ucar.edu</a><br>
>>>>> <a href="http://mailman.ucar.edu/mailman/listinfo/wrf-users" rel="noreferrer" target="_blank">http://mailman.ucar.edu/<wbr>mailman/listinfo/wrf-users</a><br>
>>>>><br>
>>>>><br>
>>>><br>
>>><br>
>><br>
><br>
-------------- next part --------------<br>
An HTML attachment was scrubbed...<br>
URL: <a href="http://mailman.ucar.edu/pipermail/wrf-users/attachments/20160906/972f706e/attachment.html" rel="noreferrer" target="_blank">http://mailman.ucar.edu/<wbr>pipermail/wrf-users/<wbr>attachments/20160906/972f706e/<wbr>attachment.html</a><br>
<br>
------------------------------<br>
<br>
______________________________<wbr>_________________<br>
Wrf-users mailing list<br>
<a href="mailto:Wrf-users@ucar.edu">Wrf-users@ucar.edu</a><br>
<a href="http://mailman.ucar.edu/mailman/listinfo/wrf-users" rel="noreferrer" target="_blank">http://mailman.ucar.edu/<wbr>mailman/listinfo/wrf-users</a><br>
<br>
<br>
End of Wrf-users Digest, Vol 145, Issue 14<br>
******************************<wbr>************<br>
</blockquote></div><br></div>