[Wrf-users] default sigma level settings [SEC=UNCLASSIFIED]

Eric Altshuler ela at cola.iges.org
Mon Jan 12 14:44:51 MST 2009 

Thanks Michael and Chris! I had a look at the routine 'compute_eta' in module_initialize_real.F, and the algorithm to compute the eta levels is VERY complicated (not some simple formula to give the distribution of levels between 0 and 1). Now just by running ncdump on the wrfinput file I can get all the levels, put them into namelist.input and tweak them if necessary.

Best regards,
Eric

----- Original Message -----
From: "Mikhail Titov" <mikhail.titov at canterbury.ac.nz>
To: "Chris Thomas" <Chris.Thomas at ga.gov.au>, wrf-users at ucar.edu
Sent: Monday, January 12, 2009 4:17:20 PM GMT -05:00 US/Canada Eastern
Subject: RE: [Wrf-users] default sigma level settings [SEC=UNCLASSIFIED]

Hello,

Would like to join this discussion. I agree with Chris about levelling and checking levels but can not agree about staggered and unstaggered levels.

>From ARW WRF basic description (page 17, Figure 3.2) and my own experience the command:
  ncdump -v ZNW wrfinput_d01
Will give unstaggered levels (basic levels for W, P, PB ...), while the command:
  ncdump -v ZNU wrfinput_d01
Will give you staggered levels (intermediate levels for U,V, ...).

It is easy to check using in WRF namelist.input eta_levels and apply "ncdump -v ZNW wrfinput_d01": eta_levels (basic, unstaggered) will be identical in namlist.input and for ZNW=.

Regards,
Michael

--------------------------------------
Dr. Mikhail Titov
Connell Wagner Ltd.
VP of the NZ Met.Society
University of Canterbury
Christchurch, New Zealand
E-mail: Mikhail.Titov at canterbury.ac.nz
Phone: (03) 364 2987 Ext: 3088
Mobile: (021) 106 5563
--------------------------------------




-----Original Message-----
From: wrf-users-bounces at ucar.edu [mailto:wrf-users-bounces at ucar.edu] On Behalf Of Chris.Thomas at ga.gov.au
Sent: Monday, 12 January 2009 2:53 p.m.
To: wrf-users at ucar.edu
Subject: FW: [Wrf-users] default sigma level settings [SEC=UNCLASSIFIED]


As an addendum to my previous post, if you are interested in how the eta levels are defined for idealized cases (as was Leo, the author of the original post) then look at the corresponding module_initialize_xxxx.F file. For example look at module_initialize_quarter_ss.F and look for where grid%znw and grid%znu are assigned.

You can also read off the eta levels straight from the wrfinput_d01 file that is created by ideal.exe (or real.exe as the case may be). For example

   ncdump -v ZNW wrfinput_d01

will give you the staggered eta levels and

   ncdump -v ZNU wrfinput_d01

Will give you the unstaggered levels.

Regards

Chris

-----Original Message-----
From: wrf-users-bounces at ucar.edu [mailto:wrf-users-bounces at ucar.edu] On Behalf Of Thomas Chris
Sent: Monday, 12 January 2009 9:04 AM
To: wrf-users at ucar.edu
Subject: FW: [Wrf-users] default sigma level settings [SEC=UNCLASSIFIED]


I think that the relevant code can be found in module_initialize_real.F (assuming you are doing a real case). Look for the subroutine compute_eta.

Regards

Chris

-----------------------------------------------------------
Christopher Thomas
Computational Modeller
Risk and Impact Analysis Group
Geoscience Australia
Ph: +61 2 6249 9757
Email: chris.thomas at ga.gov.au

-----Original Message-----
From: wrf-users-bounces at ucar.edu [mailto:wrf-users-bounces at ucar.edu] On Behalf Of Eric Altshuler
Sent: Saturday, 10 January 2009 5:08 PM
To: wrf-users
Subject: Re: [Wrf-users] default sigma level settings


Hello Jorge,

I think the point of the original question was this: What are the sigma levels chosen by default when eta_levels is NOT specified? Suppose I set e_vert = 41 but don't specify eta_levels. What is the resulting distribution of sigma level values? There must be some formula in the code that calculates the 41 sigma values in this case, but it isn't clear how the default levels are calculated for a given value of e_vert.

Best regards,

Eric L. Altshuler
Assistant Research Scientist
Center for Ocean-Land-Atmosphere Studies
4041 Powder Mill Road, Suite 302
Calverton, MD 20705-3106
USA

E-mail: ela at cola.iges.org
Phone: (301) 902-1257
Fax: (301) 595-9793

----- Original Message -----
From: "Jorge Alejandro Arevalo Borquez" <jaareval at gmail.com>
To: "anis 980" <anis_980 at sina.com>
Cc: wrf-users at ucar.edu
Sent: Thursday, January 8, 2009 12:37:39 PM GMT -05:00 US/Canada Eastern
Subject: Re: [Wrf-users] default sigma level settings

Hi,
In WRF you can give explicitly the values for vertical levels, to do this you need add eta_levels values like this:

 &domains
 eta_levels   = 1.0000, 0.9960, 0.9940, 0.9920, 0.9900,
                0.9880, 0.9850, 0.9820, 0.9780, 0.9740, 0.97, 0.965,
                0.96,   0.949,  0.937,  0.924,  0.909,
                0.892,  0.873,  0.851,  0.826,  0.798,
                0.768,  0.736,  0.702,  0.666,  0.629,
                0.5915, 0.5536, 0.5153, 0.4773, 0.44,
                0.404,  0.3695, 0.3375, 0.3085, 0.2845,
                0.2645, 0.2465, 0.2305, 0.2165, 0.2035,
                0.1915, 0.1792, 0.1667, 0.1539, 0.1407,
                0.1272, 0.1134, 0.0995, 0.0855, 0.0713,
                0.0571, 0.0520, 0.0480, 0.0429, 0.038,
                0.032,  0.0287, 0.022,  0.018,  0.0145, 0.007, 0.000,
 time_step                           = 200,
...
...


Best regards

2008/12/25 <anis_980 at sina.com>

>  Hello,
>   I am trying to run WRF ideal case em_quarter_ss, and I set 
> "s_vert=1, e_vert=41 " in namelist.input file. But I want to know the 
> sigma value of each level, does anyone know how does WRF model 
> generate sigma values according the total number of vertical levels?
> What is the default sigma value according vertical level settings?
> Best,  Leo
>
> _______________________________________________
> Wrf-users mailing list
> Wrf-users at ucar.edu http://mailman.ucar.edu/mailman/listinfo/wrf-users
>
>


--
Atentamente
Jorge Arévalo Bórquez

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