Question on using Grid nudging

[vriesdwj]

Hi,

I have a question on nudging, specially "Grid nudging using input FNL data"
What does the hour 9999 mean in "gfdda_end_h = 9999, 9999, 9999,"
We used "gfdda_end_h = 8760, 8760, 8760,", but then nudging stops after 1 year.

Regards, Wilco.

&fdda
grid_fdda = 1, 1, 1,
gfdda_inname = "wrffdda_d<domain>",
gfdda_interval_m = 360, 360, 360,
gfdda_end_h = 9999, 9999, 9999,
io_form_gfdda = 2,
fgdt = 0, 0, 0,
if_no_pbl_nudging_uv = 1, 1, 1,
if_no_pbl_nudging_t = 1, 1, 1,
if_no_pbl_nudging_q = 1, 1, 1,
if_zfac_uv = 1, 1, 1,
k_zfac_uv = 10, 10, 10,
if_zfac_t = 0, 0, 10,
k_zfac_t = 10, 10, 10,
if_zfac_q = 0, 0, 0,
k_zfac_q = 10, 10, 10,
guv = 0.0003, 0.0003, 0.0003,
gt = 0.0003, 0.0003, 0.0003,
gq = 0.0003, 0.0003, 0.0003,
if_ramping = 0,
dtramp_min = 60.0
/

 

[Ming Chen]

gfdda_end_h specifies the time in hours o stop nudging after the start of forecast.
In your case, gfdda_end_h = 8760 indicates that the nudging will stop after 1-year integration. The model behaves as expected.

 

[vriesdwj]

Hi Ming Chen,

Thanks for your reply.
Than just one more question:

How do I define in the WRF configuration that it will never stop nudging?

Regards,Wilco.

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[Ming Chen]

Wilco,
if you want the nudging to be done all the tie, you can specify a large value of gfdda_end_h that is far beyond your i integration time.