Troubleshooting WPS Geogrid.exe: Incorrect Range in Generated Static Geographical Data

[ruiyingz]

Hi All，

I am moving on to the static geographical data with WPS version 4.2 for a specific region ranging from -60S to 90N latitude and -180W to 180E, with spatial resolution of 0.25 degree. But after running geogrid.exe, the static data generated covers the entire globe from -90S to 90N. Could anyone kindly explain why this is happening and how to correctly set up the namelist.wps to generate static data only for my area of interest?

I look forward to your responses and appreciate your assistance in advance.

Below are the contents of my namelist.wps file:
#
&share
wrf_core = 'ARW',
max_dom = 1,
start_date = '1948-01-01_00:00:00',
end_date = '2020-12-31_23:00:00',
interval_seconds = 10800,
io_form_geogrid = 2,
/

&geogrid
parent_id = 1,
parent_grid_ratio = 1,
i_parent_start = 1,
j_parent_start = 1,
e_we = 1441,
e_sn = 721,
geog_data_res = 'default','default',
map_proj = 'lat-lon',
stand_lon = 0.0,
pole_lat = 90.0,
pole_lon = 0.0,
geog_data_path = '/home/path/WRFDIR/DATA/WPS_GEOG/',
/
ref_lat = 15.0, !calculated from (90+(-60))/2
ref_lon = 0,
dx = 0.25,
dy = 0.25
#

Best,
Rui

 

[Ming Chen]

Rui,
In your namelist.wps, You specify
e_we = 1441,
e_sn = 721,
dx = 0.25
dy=0.25

This covers the entire globe.

 

[ruiyingz]

Hi Ming,

Thanks for your reply. But I tried setting
e_we = 100, (or even smaller)
e_sn = 100,
dx = 0.25
dy=0.25

It still covers the entire globe.

I am wondering if it resulted from 'max_dom = 1'. btw if I set this value to 2, the generated geo_em_d01.nc still covers the entire globe (no matter how to set e_we and e_sn), but geo_em_d02.nc would cover a smaller region.

But I prefer to just set 'max_dom = 1' and use geo_em_d01.nc for my study, as it is more straightforward in my study. Could you kindly explain how to get a regional scale rather than the entire globe in this situation?

Thanks in advance,
Rui

 

[Ming Chen]

Rui,
I will do a quick test tomorrow and get back to you. We seldom run WRF in lat-lon projection and I need to refresh my memory.
Thanks for your patience.

 

[Ming Chen]

Rui,
I just did a test using the lat-on project. Below is the key options I used:

&geogrid
parent_id = 1, 1,
parent_grid_ratio = 1, 3,
i_parent_start = 1, 30,
j_parent_start = 1, 15,
e_we = 70, 31
e_sn = 60, 31,
geog_data_res = 'default','default',
dx = 0.3,
dy = 0.3,
map_proj = 'lat-lon',
ref_lat = 60.
ref_lon = 10.
stand_lon = -10.
pole_lat = 30
pole_lon = 180.
geog_data_path = '/glade/work/wrfhelp/WPS_GEOG/'
/

Attached is the plot for the domain.

WPS works as expected and I cannot repeat the issue you reported. Can you double check your files?

 

[ruiyingz]

Hi Ming,

Many thanks for your prompt reply. Yep, I was able to generate a regional scale map based on your suggestions.

However, I noticed that the order of variables in the namelist, specifically pole_lat and pole_lon, and the values of pole_lat, significantly influence the results. This might be the root cause of the issue. Please see the attached files for your reference; I conducted four different tests:

(a) ORDER and Values: pole_lat = 30, pole_lon = 180, ref_lat = 60, ref_lon = 10
(b) ORDER and Values: ref_lat = 60, ref_lon = 10, pole_lat = 30, pole_lon = 180
(c) ORDER and Values: pole_lat = 90, pole_lon = 180, ref_lat = 60, ref_lon = 10 (this resulted in a global domain, which aligns with my previous question)
(d) ORDER and Values: ref_lat = 60, ref_lon = 10, pole_lat = 90, pole_lon = 180

The results were inconsistent across these settings. Hence, I have a few questions:

What should be the proper order of these variables?
How can I set the variables if I want to obtain a range from -60S to 90N and -180W to 180E?
Could you also assist me in determining the settings for other variables, like stand_lon?
I greatly appreciate your help and look forward to your response.

Best regards,
Rui

 

[Ming Chen]

Rui,

Thanks for the follow-up.

(1) I expect that options (1) and (2) yield the same result, options (3) and (4) yield the same result. Please let me know if I am wrong.
Basically the order of the namelist options doesn't really matter. If their values are the same, then they should yield same results.

(2) with different pole-lat, you definitely will get different results. This option actually determines the rotation of the region domain, and it must be specified correctly. Just for your information, please take a look at the document:

The WRF Preprocessing System (WPS) — WRF Users Guide documentation

Please let me know if you have more questions.

 

[ruiyingz]

Thanks Ming. Upon further examination, I've discovered that the order of the variables in the namelist does not affect the results, as you pointed out.

However, a surprising element has come into play: the placement of the slash ("/") between geog_data_path and ref_lat in the namelist. This small detail seems to significantly influence the outcomes.

Please have a look at the attached files in my previous post, specifically the comparisons between options (a) and (b).
The differences in results can be attributed to the placement of the slash in the namelist.

So I guess it is worth noting this issue on line 36 in this given example in Github: WPS/namelist.wps.global at master · wrf-model/WPS.

Best,
Rui