wrong results for vertical interpolation

[mihaela]

Dear colleagues,
I would be very grateful to you if you could suggest me a solution to the following problem:
I am getting wrong results when I interpolate the "Input levels" to the "Output levels" below using v_interp.f with the namelist namelist.v_interp

Input levels:
0.9965, 0.988, 0.9765, 0.962, 0.944, 0.9215, 0.8945, 0.8603331, 0.8209995,
0.7816658, 0.7423322, 0.6876204, 0.6201558, 0.5577776, 0.5001666,
0.4470201, 0.3980519, 0.352991, 0.3115812, 0.2735803, 0.2387594,
0.2069025, 0.1778055, 0.1512759, 0.1271324, 0.1054426, 0.08629248,
0.06946232, 0.05467107, 0.04167173, 0.03024721, 0.02020674, 0.01138263,
0.00362753 ;
Output levels
eta_levels = 1.000, 0.999, 0.998, 0.997, 0.995,
0.992, 0.989, 0.985, 0.980, 0.974,
0.967, 0.959, 0.950, 0.940, 0.928,
0.914, 0.898, 0.880, 0.860, 0.838,
0.814, 0.788, 0.760, 0.730, 0.695,
0.655, 0.610, 0.565, 0.515, 0.465,
0.415, 0.360, 0.305, 0.245, 0.188,
0.132, 0.080, 0.035, 0.000

Many thanks in advance.
Best regards,
Mihaela

 

[kwerner]

This topic has been moved to the WRF Utilities section of the forum, as the v_interp program is a utility. Someone will follow up with this post soon.

 

[Ming Chen]

When adding vertical levels, please keep the first- and the last-half levels the same as in the input file itself. If levels are added outside the range, the result might be wrong. Please double check your settings.

 

[mihaela]

Thank you very much for the answer.
Still I would like to understand why the rule does not apply always.
When I use the following output levels it works:
1, 0.997, 0.993, 0.987, 0.979, 0.97, 0.959, 0.946, 0.931, 0.915, 0.896,
0.875, 0.853, 0.828, 0.802, 0.774, 0.743, 0.711, 0.677, 0.641, 0.604,
0.565, 0.525, 0.484, 0.444, 0.403, 0.363, 0.323, 0.285, 0.249, 0.214,
0.181, 0.151, 0.124, 0.099, 0.076, 0.056, 0.039, 0.024, 0.011, 0 ;

 

[Ming Chen]

This utility has no extrapolation function. It behaves to increase the vertical resolution within the original vertical range. To better understand this utility, please read relevant codes and publications.