# height of first layer

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#### ensiyeh

##### New member
Hi
I have a problem with WRF-ARW. In my simulation, the first layer must be
less than 40 m. I chang layers number until 100, but my first layer height
is 54 m. I attached the name lists. Could you help me, please?
Thank you
View attachment New Text Document (4).txt

In this case you need to manually specify the model levels. Below is an example:
eta_levels = 1.00000 , 0.99307 , 0.98348 , 0.97105 , 0.95551 ,
0.93651 , 0.91363 , 0.88644 , 0.85460 , 0.81855 ,
0.77877 , 0.73579 , 0.69016 , 0.64246 , 0.59329 ,
0.54573 , 0.50104 , 0.45908 , 0.41972 , 0.38281 ,
0.34824 , 0.31589 , 0.28563 , 0.25735 , 0.23096 ,
0.20635 , 0.18343 , 0.16209 , 0.14226 , 0.12384 ,
0.10677 , 0.09095 , 0.07633 , 0.06282 , 0.05036 ,
0.03889 , 0.02835 , 0.01868 , 0.00983 , 0.00000
You need to change the values based on your case.

Thank you. @Ming Chen
Is there any relation between these numbers in "eta_levels "? I want to set "e_vert = 36", so I must have 36 numbers between 1 and 0. But what about the other numbers? How can I calculate them? Could you help me, please?
Thank you

There is no specific formula to calculate the values of eta levels. They are experimental and one needs to specify based on his/her case.

Hi Ming,

Thank you.