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REAL how to split the lowest eta level in two layers

F

francescomaicu

Member
Dear all,
I am running REAL program to generate the WRF input files with the followinf namelist:
Code: 
 &domains
 time_step                           = 20,
 time_step_fract_num                 = 0,
 time_step_fract_den                 = 1,
 max_dom                             = 1,
 e_we                                = 1658,
 e_sn                                = 752,
 e_vert                              = 40,
 p_top_requested                     = 5000,
 num_metgrid_levels                  = 26,
 num_metgrid_soil_levels             = 4,
 dx                                  = 4632.395,
 dy                                  = 4632.395,
 grid_id                             = 1,
 parent_id                           = 0,
 i_parent_start                      = 1,
 j_parent_start                      = 1,
 parent_grid_ratio                   = 1,
 parent_time_step_ratio              = 1,
 feedback                            = 1,
 smooth_option                       = 0

the other missing namelist entries are default, in particular for my case:
dzbot (50m), dzstretch(_s and _u) and auto_levels_opt (=2) . The resulting vertical discretization is as follows:


Code: 
Full level index =    1     Height =     0.0 m
Full level index =    2     Height =    50.0 m      Thickness =   50.0 m
Full level index =    3     Height =   113.9 m      Thickness =   63.9 m
Full level index =    4     Height =   195.2 m      Thickness =   81.3 m
Full level index =    5     Height =   298.0 m      Thickness =  102.8 m
Full level index =    6     Height =   427.2 m      Thickness =  129.1 m
Full level index =    7     Height =   587.8 m      Thickness =  160.7 m
Full level index =    8     Height =   785.5 m      Thickness =  197.7 m
Full level index =    9     Height =  1025.6 m      Thickness =  240.0 m
Full level index =   10     Height =  1312.6 m      Thickness =  287.0 m
Full level index =   11     Height =  1649.6 m      Thickness =  337.0 m
Full level index =   12     Height =  2037.7 m      Thickness =  388.2 m
Full level index =   13     Height =  2475.6 m      Thickness =  437.9 m
Full level index =   14     Height =  2959.3 m      Thickness =  483.7 m
Full level index =   15     Height =  3485.1 m      Thickness =  525.8 m
Full level index =   16     Height =  4056.1 m      Thickness =  570.9 m
Full level index =   17     Height =  4675.0 m      Thickness =  618.9 m
Full level index =   18     Height =  5344.9 m      Thickness =  669.8 m
Full level index =   19     Height =  6068.4 m      Thickness =  723.5 m
Full level index =   20     Height =  6841.5 m      Thickness =  773.1 m
Full level index =   21     Height =  7598.1 m      Thickness =  756.6 m
Full level index =   22     Height =  8338.2 m      Thickness =  740.1 m
Full level index =   23     Height =  9061.9 m      Thickness =  723.7 m
Full level index =   24     Height =  9769.1 m      Thickness =  707.2 m
Full level index =   25     Height = 10459.8 m      Thickness =  690.7 m
Full level index =   26     Height = 11134.1 m      Thickness =  674.2 m
Full level index =   27     Height = 11791.8 m      Thickness =  657.8 m
Full level index =   28     Height = 12433.1 m      Thickness =  641.3 m
Full level index =   29     Height = 13057.9 m      Thickness =  624.8 m
Full level index =   30     Height = 13678.6 m      Thickness =  620.7 m
Full level index =   31     Height = 14299.3 m      Thickness =  620.7 m
Full level index =   32     Height = 14919.9 m      Thickness =  620.7 m
Full level index =   33     Height = 15540.6 m      Thickness =  620.7 m
Full level index =   34     Height = 16161.3 m      Thickness =  620.7 m
Full level index =   35     Height = 16782.0 m      Thickness =  620.7 m
Full level index =   36     Height = 17402.6 m      Thickness =  620.7 m
Full level index =   37     Height = 18023.3 m      Thickness =  620.7 m
Full level index =   38     Height = 18644.0 m      Thickness =  620.7 m
Full level index =   39     Height = 19264.7 m      Thickness =  620.7 m
Full level index =   40     Height = 19885.3 m      Thickness =  620.7 m

I would like to split the lowest level minto two layers (20-30m) and maintain unaltered the remaining levels.
So I tried to change the thickess of the first layer and add a layer with:
Diff: 
dzbot = 30
evert = 41
but I get after running REAL :




Code: 
Full level index =    1     Height =     0.0 m
Full level index =    2     Height =    30.0 m      Thickness =   30.0 m
Full level index =    3     Height =    68.6 m      Thickness =   38.6 m
Full level index =    4     Height =   118.1 m      Thickness =   49.5 m
Full level index =    5     Height =   181.5 m      Thickness =   63.3 m
Full level index =    6     Height =   262.1 m      Thickness =   80.6 m
Full level index =    7     Height =   364.1 m      Thickness =  102.0 m
Full level index =    8     Height =   492.2 m      Thickness =  128.1 m
Full level index =    9     Height =   651.7 m      Thickness =  159.4 m
Full level index =   10     Height =   847.9 m      Thickness =  196.3 m
Full level index =   11     Height =  1086.3 m      Thickness =  238.4 m
Full level index =   12     Height =  1371.4 m      Thickness =  285.1 m
Full level index =   13     Height =  1706.4 m      Thickness =  335.0 m
Full level index =   14     Height =  2092.5 m      Thickness =  386.1 m
Full level index =   15     Height =  2528.3 m      Thickness =  435.8 m
Full level index =   16     Height =  3010.0 m      Thickness =  481.7 m
Full level index =   17     Height =  3533.7 m      Thickness =  523.7 m
Full level index =   18     Height =  4102.3 m      Thickness =  568.6 m
Full level index =   19     Height =  4718.7 m      Thickness =  616.4 m
Full level index =   20     Height =  5385.9 m      Thickness =  667.1 m
Full level index =   21     Height =  6106.5 m      Thickness =  720.6 m
Full level index =   22     Height =  6883.2 m      Thickness =  776.7 m
Full level index =   23     Height =  7676.1 m      Thickness =  792.8 m
Full level index =   24     Height =  8450.7 m      Thickness =  774.7 m
Full level index =   25     Height =  9207.3 m      Thickness =  756.5 m
Full level index =   26     Height =  9945.6 m      Thickness =  738.4 m
Full level index =   27     Height = 10665.9 m      Thickness =  720.2 m
Full level index =   28     Height = 11367.9 m      Thickness =  702.1 m
Full level index =   29     Height = 12051.9 m      Thickness =  683.9 m
Full level index =   30     Height = 12717.6 m      Thickness =  665.8 m
Full level index =   31     Height = 13369.1 m      Thickness =  651.5 m
Full level index =   32     Height = 14020.6 m      Thickness =  651.5 m
Full level index =   33     Height = 14672.1 m      Thickness =  651.5 m
Full level index =   34     Height = 15323.6 m      Thickness =  651.5 m
Full level index =   35     Height = 15975.1 m      Thickness =  651.5 m
Full level index =   36     Height = 16626.6 m      Thickness =  651.5 m
Full level index =   37     Height = 17278.1 m      Thickness =  651.5 m
Full level index =   38     Height = 17929.6 m      Thickness =  651.5 m
Full level index =   39     Height = 18581.1 m      Thickness =  651.5 m
Full level index =   40     Height = 19232.6 m      Thickness =  651.5 m
Full level index =   41     Height = 19884.1 m      Thickness =  651.5 m

That is not exactly what I would like.
Do you have any suggestion for that?
Thank you
 
Hi,
You can use the "eta_levels" namelist parameter to specify each layer, instead of letting the model choose it for you. Take a look in WRF/run/README.namelist for additional information on this parameter.
 
Hi !
thank you for the reply. I got your point.
BTW I have a small concern. With eta-level the thickness of the first (surface) layer should vary with the topography, so the thickness shouldn't be constaant all over the domain. On the contrary it looks like that if I set dzbot , I keep fixed the thickness of the first layer all over the domain. Is there something that I am missing?
 
Hi,
The levels are a hybrid vertical coordinate. Take a look at the description here and let me know if this makes sense.
 
Hi @kwerner ,
yes it makes sense. Looking here (bottom of page 3), I understand that the first eta level is calculated to set the desired value of dzbot.
I have a second point to investigate. I am wondering wether the transition to isobaric levels occurs too close or intersecting the mountains (4500m approx).
The transition occurs by default for eta(c)=0.2, so I want to know the corresponding height, I can look at the rsl.out.0000 of the real program and read the value in the third column corresponding to the 0.2 value in the fourth column, i.e. 11904.09 (m).
Am I right?

Code: 
Using sfcprs3 to compute psfc
 using new automatic levels program
           1   50.00000       50.00000      0.9938148
           2   64.00000       114.0000      0.9859507       1.280000
           3   81.56160       195.5616      0.9760143       1.274400
           4   103.3692       298.9308      0.9635576       1.267375
           5   130.1058       429.0366      0.9480931       1.258652
           6   162.3666       591.4032      0.9291238       1.247958
           7   200.5314       791.9346      0.9061912       1.235053
           8   244.6057       1036.540      0.8789424       1.219787
           9   294.0546       1330.595      0.8472080       1.202158
          10   347.6837       1678.279      0.8110777       1.182378
          11   403.6352       2081.914      0.7709491       1.160927
          12   459.5572       2541.471      0.7275254       1.138546
          13   512.9473       3054.418      0.6817554       1.116177
          14   564.2420       3618.660      0.6345036       1.100000
          15   620.6662       4239.326      0.5860305       1.100000
          16   682.7328       4922.059      0.5366501       1.100000
          17   751.0062       5673.065      0.4867300       1.100000
          18   826.1068       6499.172      0.4366881       1.100000
   25416.39       6499.172              39          18
          19   900.8199       7399.992      0.3873971
          20   900.8199       8300.812      0.3430713
          21   900.8199       9201.633      0.3032106
          22   900.8199       10102.45      0.2673653
          23   900.8199       11003.27      0.2351308
          24   900.8199       11904.09      0.2061434
          25   900.8199       12804.91      0.1800760
          26   900.8199       13705.73      0.1566344
          27   900.8199       14606.55      0.1355543
          28   900.8199       15507.38      0.1165976
          29   900.8199       16408.20      9.9550486E-02
          30   900.8199       17309.02      8.4220596E-02
          31   900.8199       18209.84      7.0434950E-02
          32   900.8199       19110.66      5.8037974E-02
          33   900.8199       20011.48      4.6889815E-02
          34   900.8199       20912.30      3.6864650E-02
          35   900.8199       21813.12      2.7849343E-02
          36   900.8199       22713.94      1.9742193E-02
          37   900.8199       23614.76      1.2451692E-02
          38   900.8199       24515.58      5.8956160E-03
          39   900.8199       25416.40     -5.1398029E-08
 
Last edited:
Yes, 11.9km is where eta=0.2.
4.5 km is probably not too close, but the layers will be thinner than over lower elevations - maybe 50% less,
 
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