Problems using SRTM and ASTER data

[larissafrj]

Hello everyone!


I’m having a little problem with the assimilation of topographic data in wrf.

I used as reference the discussion at the topic below and the User’s Guide to assimilate SRTM and ASTER data on WRF.
https://forum.mmm.ucar.edu/phpBB3/viewtopic.php?f=30&t=8359&p=14133&hilit=srtm+topography#p14133



Firstly, I downloaded several GeoTiff files for the region of my interest and merged these files using python gdal.
> gdal_merge.py -init 255 -o saida.tif carta1.tif carta2.tif carta3.tif [… até a] cartaN.tif 

Then, I used the convertgeotiff routine to create the topographic files readable for wrf for each database.

./convert_geotiff -w 4 -t 1200 arquivoSRTM.tif


This script created automatically several binaries files and the index file bellow.

Example for SRTM 30 meter:

projection = regular_ll
known_x = 1
known_y = 18001
known_lat = -19.999722
known_lon = -47.000278
dx = 2.784729e-04
dy = 2.784729e-04
type = continuous
signed = yes
units = "NO UNITS"
description = "NO DESCRIPTION"
wordsize = 4
tile_x = 1200
tile_y = 1200
tile_z = 1
tile_bdr = 3
missing_value = 0.000000
scale_factor = 1.000000
row_order = bottom_top
endian = little
missing_value = 32768

Finally, I adapted the GEOGRID.TBL and the namelist.wps and ran successfully 3 wrf simulations using the default topographic database, SRTM, and ASTER. However, when I calculated the difference between HGT variable between the domains of 500m I find out differences in topography that reach more than 500m (my region has a complex topography with a lot of hills and valleys).

I looked at the data closely and I discovered that using the Coastline as a reference that SRTM and ASTER data has the topographic data shifted from default data and between each other.

So… Does anyone have a similar problem?


Best Regards,

Larissa

 

[kwerner]

Hi Larissa,
Unfortunately I'm not aware of anyone in our group who is using these topography datasets, so I'm not sure which is correct, or what the solution is. Hopefully someone else who has experience will see the problem and have advice. It may help to post this forum inquiry link to any other user posts that have used these datasets to get the attention of those more familiar with the data.

 

[tmazzett]

we were using the SRTM 3s topos that are on the cheyenne GEOG data folder and we notice that the georeferencing was 1.0 degrees latitude too far north. I hope this helps.