WRF 4.1.5 spectral nudging produces identical results to no-nudging run

H

hkjin

New member
Hello,
I am trying to use spectral nudging with WRF version 4.1.5. The total simulation period is one day, and I plan to apply spectral nudging only at 12 UTC.
I modified the &fdda section in namelist.input to enable spectral nudging, but the WRF outputs are the same as the case without nudging. It is unclear whether spectral nudging is actually taking effect.

Could you please advise which settings I should modify or what I should check to make spectral nudging work properly?
I have attached my namelist.input, log files, and NetCDF attributes for reference.
Thank you in advance.
 

Attachments

I fixed this problem by modifying the namelist.input as follows:

&fdda
!---- turn on spectral nudging (domain = 1) ----
grid_fdda = 2,
gfdda_inname = "wrffdda_d<domain>",
gfdda_interval_m = 1440,
gfdda_end_h = 24,
io_form_gfdda = 2,
fgdt = 0,

!---- spectral nudging options ----
fgdtzero = 0,
if_no_pbl_nudging_uv = 1,
if_no_pbl_nudging_t = 1,
if_no_pbl_nudging_ph = 1,
if_no_pbl_nudging_q = 1,
guv = 0.0003,
if_zfac_uv = 1,
k_zfac_uv = 15,
dk_zfac_uv = 1,
gt = 0.0003,
if_zfac_t = 1,
k_zfac_t = 15,
dk_zfac_t = 1,
gph = 0.0003,
if_zfac_ph = 1,
k_zfac_ph = 15,
dk_zfac_ph = 1,
gq = 0.00001,
if_zfac_q = 1,
k_zfac_q = 15,
dk_zfac_q = 1,
ktrop = 0,
xwavenum = 4,
ywavenum = 4,
 
Ming Chen said:
Thanks for the update. x- and y-wavenum are two important factors that affect spectral nudging.
Click to expand...
Thank you for your comment. The input data have a horizontal resolution of 1 degree, and the model resolution is 1/12 degree. Should the choice of wavenumber be based on the resolution of the input data, or on the model resolution? I am not sure whether 3 or 4 would be better.
 
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