[Wrf-users] Question about levels in wrf

Tue Sep 6 14:04:32 MDT 2016

Hi Brandt Naxwell,

thank you very much for all your very clear explanations.

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?

Thank you again.

José Augusto P. Veiga
CREA n.: 24161

======================================
Universidade do Estado do Amazonas
Departamento de Meteorologia
Escola Superior de Tecnologia (EST)
======================================
Av. Darcy Vargas, 1200, Manaus-AM Brasil
Work phone:    (92) 3878 4317, Ramal 4317
Skype: veiga_j.a.p.
======================================
CV: http://lattes.cnpq.br/4027612512091565
Site: https://scientificmet.wordpress.com
======================================

On Tue, Sep 6, 2016 at 3:06 PM, Brandt Maxwell - NOAA Federal <
brandt.maxwell at noaa.gov> wrote:

> Jose,
>
> 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).
>
> 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.
>
> Later...
> Brandt Maxwell
> National Weather Service/San Diego
>
>
>
>
> On Sun, Sep 4, 2016 at 4:03 PM, Jose Augusto Paixão Veiga <
> veiga.uea at gmail.com> wrote:
>
>> Dear all,
>>
>> I am using the following eta levels in my runs with WRF (38 in this
>> case).
>>
>>
>>
>> *eta_levels                          = 1.000, 0.995, 0.990, 0.985,
>> 0.980, *
>>
>> *                                      0.970, 0.960, 0.950, 0.940,
>> 0.930, *
>>
>> *                                       0.920, 0.910, 0.900, 0.880,
>> 0.860, *
>>
>> *                                       0.830, 0.800, 0.770, 0.740,
>> 0.710, *
>>
>> *                                       0.680, 0.640, 0.600, 0.560,
>> 0.520, *
>>
>> *                                       0.480, 0.440, 0.400, 0.360,
>> 0.320, *
>>
>> *                                       0.280, 0.240, 0.200, 0.160,
>> 0.120, *
>>
>> *                                       0.080, 0.040, 0.000*
>>
>>
>>
>> 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?
>>
>> I really appreciate any comment on this issue.
>>
>> Thanks.
>>
>>
>>
>>
>>
>>
>> José Augusto P. Veiga
>> CREA n.: 24161
>>
>> ======================================
>> Universidade do Estado do Amazonas
>> Departamento de Meteorologia
>> Escola Superior de Tecnologia (EST)
>> ======================================
>> Av. Darcy Vargas, 1200, Manaus-AM Brasil
>> Work phone:    (92) 3878 4317, Ramal 4317
>> Skype: veiga_j.a.p.
>> ======================================
>> CV: http://lattes.cnpq.br/4027612512091565
>> Site: https://scientificmet.wordpress.com
>> ======================================
>>
>>
>>
>>
>> _______________________________________________
>> Wrf-users mailing list
>> Wrf-users at ucar.edu
>> http://mailman.ucar.edu/mailman/listinfo/wrf-users
>>
>>
>
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