known_lat , known_lon and resolution of static input data

Dataset specific topics involving WPS.

known_lat , known_lon and resolution of static input data

Postby centurion555 » Fri May 26, 2017 10:29 am

Dear all,

I'm using WRFV3.9. I have successfully completed test run using 1 Arc-Second Global SRTM dataset located at:

https://lta.cr.usgs.gov/SRTM1Arc

I had no problems writing this data to geogrid format. But I have two questions:

1) What are exactly known_lat, known_lon in index file ? As far as I understand they are the coordinates of the lower left grid box of the input raster data. But are they coordinates of the corner or center of the lower left grid box ? If I see index file from the global 30s landuse data "landuse_30s_with_lakes" :

projection=regular_ll
dx=0.00833333
dy=0.00833333
known_x=1.0
known_y=1.0
known_lat=-89.99583
known_lon=-179.99583

it looks like they are coordinate of the center of the first grid box (lower left) grid box. Please clarify.

2) I have nested domain 3.0 km => 1.0 km => 333.33 m => 111.11 m and I want to use the above mentioned SRTM-1Arc and 100m CORINE Landuse (mapped to 24 USGS categories) for these four Domains . But WRF tutorial "namelist.wps: Best Practices" recommends to choose a resolution of input data that is slightly better than the grid resolution for the domain. As I have only one resolution of input data I want to use, what is best way to proceed? Should I upscale to create coarser resolution input datasets or use different interpolation methods for different domains .
centurion555
 
Posts: 2
Joined: Fri May 26, 2017 9:46 am

Re: known_lat , known_lon and resolution of static input dat

Postby centurion555 » Thu Jul 27, 2017 5:31 am

Still no reply ?
centurion555
 
Posts: 2
Joined: Fri May 26, 2017 9:46 am

Re: known_lat , known_lon and resolution of static input dat

Postby gadelha » Fri May 18, 2018 2:59 pm

I´m new with that but I think this will help. I´m dealing with that these days and I get this:

If you have a tif file you can use gdal program to find the lower left corner. In my case:

wrfoperador@dpns31:~/geog/srtm> gdalinfo srtm_28_17.tif
Driver: GTiff/GeoTIFF
Files: srtm_28_17.tif
Size is 6001, 6001
Coordinate System is:
GEOGCS["WGS 84",
DATUM["WGS_1984",
SPHEROID["WGS 84",6378137,298.257223563,
AUTHORITY["EPSG","7030"]],
AUTHORITY["EPSG","6326"]],
PRIMEM["Greenwich",0],
UNIT["degree",0.0174532925199433],
AUTHORITY["EPSG","4326"]]
Origin = (-45.000416303460952,-19.999583236485876)
Pixel Size = (0.000833333333333,-0.000833333333333)
Metadata:
AREA_OR_POINT=Area
Image Structure Metadata:
INTERLEAVE=BAND
Corner Coordinates:
Upper Left ( -45.0004163, -19.9995832) ( 45d 0' 1.50"W, 19d59'58.50"S)
Lower Left ( -45.0004163, -25.0004166) ( 45d 0' 1.50"W, 25d 0' 1.50"S)
Upper Right ( -39.9995830, -19.9995832) ( 39d59'58.50"W, 19d59'58.50"S)
Lower Right ( -39.9995830, -25.0004166) ( 39d59'58.50"W, 25d 0' 1.50"S)
Center ( -42.4999996, -22.4999999) ( 42d30' 0.00"W, 22d30' 0.00"S)
Segmentation fault (core dumped)
wrfoperador@dpns31:~/geog/srtm>

So I set my index file as:

type = continuous
signed = no
projection = regular_ll
dx = 0.000833333333333333
dy = 0.000833333333333333
row_order = top_bottom
missing_value=-32768
known_x = 1.0
known_y = 1.0
known_lat = -25.0004166
known_lon = -45.0004163
wordsize = 2
tile_x = 6001
tile_y = 6001
tile_z = 1
tile_bdr=0
units="meters MSL"
description="Topography height SRTM 90 m DEM Version 4"
gadelha
 
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Joined: Wed Aug 12, 2009 10:11 am


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