Weird behavior in WPS when using polar stereographic projection

[Whereby]

Dear Sir or Madam,

I'm running WRF in year 2023, and trying to update land use data with MODIS/061/MCD12Q1. I'm using polar stereographic projection, my namelist.wps is shown below. I have changed my GEOGRID.TBL, and cci2023 refers to the modis data.

```
&share
wrf_core = 'ARW',
max_dom = 1,
start_date = '2023-02-28_18:00:00','2019-08-03_00:00:00',
end_date = '2023-11-01_06:00:00','2019-09-04_12:00:00',
interval_seconds = 21600
io_form_geogrid = 2,
/

&geogrid
parent_id = 1, 1,
parent_grid_ratio = 1, 3,
i_parent_start = 1, 53,
j_parent_start = 1, 25,
e_we = 200, 220,
e_sn = 200, 214,
geog_data_res = 'cci2023+default','cci2020+default',
dx = 108000,
dy = 108000,
map_proj = 'polar',
ref_lat = 90.00,
ref_lon = -98.00,
truelat1 = 45.0,
truelat2 = 1.0,
stand_lon = -98.0,
geog_data_path = '/data8/huangty/geog_total'
/

&ungrib
out_format = 'WPS',
prefix = 'GFS',
/

&metgrid
fg_name = 'GFS'
io_form_metgrid = 2,
/
```

However, when I check the geo_em.d01.nc, I found out that in LANDUSEF and LANDMASK, there is something weird. Here is the picture produced by ncview showing the result of LANDMASK.

At first, my modis data is not complete, with the range of 85°S and 85°N and -179°W to 179°E. In this case, it may make sense that there is no data around 90°N and 180°E. But when trying to fix the problem, I download the modis data with full range, gdalinfo always shows that
```
Upper Left (-180.0044166, 90.0022083) (180d 0'15.90"W, 90d 0' 7.95"N)
Lower Left (-180.0044166, -90.0022083) (180d 0'15.90"W, 90d 0' 7.95"S)
Upper Right ( 180.0044166, 90.0022083) (180d 0'15.90"E, 90d 0' 7.95"N)
Lower Right ( 180.0044166, -90.0022083) (180d 0'15.90"E, 90d 0' 7.95"S)
Center ( 0.0000000, 0.0000000) ( 0d 0' 0.01"E, 0d 0' 0.01"N)
```
which surpasses 180° in longitude and 90° in latitude, while geogrid.exe cannot deal with those surpassing data either. Is there anything I can do to fix it?

Thanks,
Tim

 

[Ming Chen]

Tim,
I don't have any experiences fixing input static datafile. We always use static files like MODIS as is. Sorry that we cannot help with this issue.
Please update your solution if you eventually solve this problem, so that other users who have the same issue may benefit form your solution. Thanks in advance.

 

[Whereby]

Dear Ming,
Thanks for your reply. After some careful inspection, I managed to find out the solution. To solve this, of course you need to download dataset with full range, in case to avoid strange data missing around 90°N and 180°E. For MODIS landuse data, there is some points whose longitude (latitude) surpass 180° (90°N), like what I mentioned above, and geogrid.exe cannot process them. The only thing to do is to change the index file in your geographical data path, make sure set the parameter known_x and known_y to a data point whose longitude (latitude) is within 180° (90°N). For easy calculation, you may choose the point (0°N, 0°E) as your known point, and it's convient to calculate its x and y by dividing tile_x and tile_y with 2.
I hope this may help!
Tim

 

[Ming Chen]

Tim
Thank you very much for the update!