Scheduled Downtime
On Friday 21 April 2023 @ 5pm MT, this website will be down for maintenance and expected to return online the morning of 24 April 2023 at the latest

Help with nudging (fdda)

This post was from a previous version of the WRF&MPAS-A Support Forum. New replies have been disabled and if you have follow up questions related to this post, then please start a new thread from the forum home page.

aztec2021

New member
Hi. I was wondering if I could get some help on how to set up a WRF run with nudging. According to the what I have been able to find in the WRF users' pages, I have added the following lines to my namelist.input to obtain nudging:
Code:
 &fdda
 grid_fdda                           = 1,
 gfdda_inname                        = "wrffdda_d01",
 gfdda_interval_m                    = 360,
 gfdda_end_h                         = 48,
 io_form_gfdda                       = 2,
 /

REAL.exe works fine and generates the wrffdda_d01 file as expected. WRF.exe also runs, however, the results are exactly the same as without nudging. Differences between nudged and unnudged 9-day runs are equal to zero for all fields for all output times.

Inspection of the log files indicates that nudging is apparently happening (see below):

Code:
D01 3-D analysis nudging reads new data at time =      0.000 min.
D01 3-D analysis nudging bracketing times =     0.00  360.00 min.
D01 3-D analysis nudging reads new data at time =    360.000 min.
D01 3-D analysis nudging bracketing times =   360.00  720.00 min.

What am I doing wrong? My namelist is attached.

I also noticed that, despite setting "gfdda_end_h = 48", the wrffdda_d01 file covers the entire length of the run, which is 9 days. It seems like WRF is ignoring gfdda_end_h.

Any help will be much appreciated. Cheers
 

Attachments

  • namelist.input
    5.3 KB · Views: 60
Hi,
I just run a test case using WRFV4.3. I also copy your &fdda section to my namelist.input. The fdda nudging option works just fine and I can see obvious impacts of grid nudging. Attached is the difference of wrfout with and without nudging after 36 hours f integration.
I also attach the names;list.input I used just in case you want to take a look. Would you please double check your results and et me know if you come up with some new information. Thanks.
 

Attachments

  • namelist.input
    6.6 KB · Views: 112
Top