Dear WRF support team,

I am using WRF version 4.1.3. over several mountain regions with domains of 25 km, 5 km, 1 km, 200 m, 40 m. I downloaded 1) SRTM1 data (~30 m) via the USGS EarthExplorer, and 2) ASTGTM (~30 m) via EarthDataSearch from Nasa, merged all tif files to one big tif file for each SRTM1 and ASTGTM, and then followed steps 4-8 from this post: https://forum.mmm.ucar.edu/phpBB3/viewtopic.php?t=9628

When running geogrid and plotting the output together with shapefiles of the region, I see large shifts for both 1) SRTM1 and 2) ASTGTM. I have attached the plots, where you can see that the shape aligns well when plotted on the original SRTM1/ASTGTM tif file, but not for WRF geo_em output. However, I did a test with the default USGS GMTED2010 30 arc-sec data from WPS (for 30 km, 10 km, 3.33 km, 1.11 km domains), and there is NO shift here.

My input SRTM1/ASTGTM tif files have the coordinate reference system (crs): "+proj=longlat +datum=WGS84 +no_defs".

My WRF-model uses Lambert conformal conic (LCC) projection.

I have read this paper (https://www.researchgate.net/publication/258805934_Overlapping_Interests_The_Impact_of_Geographic_Coordinate_Assumptions_on_Limited-Area_Atmospheric_Model_Simulations), where a huge shift could be seen because the data was transformed from WGS84 to the sphere BEFORE they were ingested and remapped to the WRF domains by geogrid.exe - but this does not seem to be the case for me, if I understand correctly, because I am using WGS84 for my input data.

Can you please help me? Thanks a lot!

My index file for SRTM1 data () looks as follows:

======================================================

projection = regular_ll

known_x = 1

known_y = 21601

known_lat = 55.000137

known_lon = -123.000275

dx = 5.524358e-04

dy = 2.762179e-04

type = continuous

signed = yes

units = "meters MSL"

description = "Topography height"

wordsize = 4

tile_x = 2291

tile_y = 2291

tile_z = 1

tile_bdr = 3

missing_value = 32768

scale_factor = 1.000000

row_order = bottom_top

endian = little

==================================

I have also tried to actually implement different coordinate reference system (crs) transformations to the original SRTM1 file (with "+proj=longlat +datum=WGS84 +no_defs") BEFORE using convert_geotiff:

1) I transformed it to regular lat long, because I had the suspicion that convert_geotiff assumes that --> didn't help, I can still see the shift

2) I transformed it to LCC, but was unsuccessful so far (HGT_M shows 0 in the geo_em files)

I am using WRF version 4.1.3. over several mountain regions with domains of 25 km, 5 km, 1 km, 200 m, 40 m. I downloaded 1) SRTM1 data (~30 m) via the USGS EarthExplorer, and 2) ASTGTM (~30 m) via EarthDataSearch from Nasa, merged all tif files to one big tif file for each SRTM1 and ASTGTM, and then followed steps 4-8 from this post: https://forum.mmm.ucar.edu/phpBB3/viewtopic.php?t=9628

When running geogrid and plotting the output together with shapefiles of the region, I see large shifts for both 1) SRTM1 and 2) ASTGTM. I have attached the plots, where you can see that the shape aligns well when plotted on the original SRTM1/ASTGTM tif file, but not for WRF geo_em output. However, I did a test with the default USGS GMTED2010 30 arc-sec data from WPS (for 30 km, 10 km, 3.33 km, 1.11 km domains), and there is NO shift here.

My input SRTM1/ASTGTM tif files have the coordinate reference system (crs): "+proj=longlat +datum=WGS84 +no_defs".

My WRF-model uses Lambert conformal conic (LCC) projection.

I have read this paper (https://www.researchgate.net/publication/258805934_Overlapping_Interests_The_Impact_of_Geographic_Coordinate_Assumptions_on_Limited-Area_Atmospheric_Model_Simulations), where a huge shift could be seen because the data was transformed from WGS84 to the sphere BEFORE they were ingested and remapped to the WRF domains by geogrid.exe - but this does not seem to be the case for me, if I understand correctly, because I am using WGS84 for my input data.

Can you please help me? Thanks a lot!

My index file for SRTM1 data () looks as follows:

======================================================

projection = regular_ll

known_x = 1

known_y = 21601

known_lat = 55.000137

known_lon = -123.000275

dx = 5.524358e-04

dy = 2.762179e-04

type = continuous

signed = yes

units = "meters MSL"

description = "Topography height"

wordsize = 4

tile_x = 2291

tile_y = 2291

tile_z = 1

tile_bdr = 3

missing_value = 32768

scale_factor = 1.000000

row_order = bottom_top

endian = little

==================================

I have also tried to actually implement different coordinate reference system (crs) transformations to the original SRTM1 file (with "+proj=longlat +datum=WGS84 +no_defs") BEFORE using convert_geotiff:

1) I transformed it to regular lat long, because I had the suspicion that convert_geotiff assumes that --> didn't help, I can still see the shift

2) I transformed it to LCC, but was unsuccessful so far (HGT_M shows 0 in the geo_em files)