Jbeezley at 08:12, 11 September 2012

2012-09-11T08:12:13Z

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			When dealing with real data, it is often necessary to reproject and interpolate raw data sources onto a WRF simulation grid. This is possible
			using WPS in a manner similar to the method used [[How to run WRF-Fire with real data\|here]]. This page illustrates this procedure on
			MODIS heat flux data. The source data is converted and interpolated from its native geotiff format into a WRF compatible netCDF file where it can be
			merged into a wrfinput file or analyzed using standard netCDF tools.

			=Converting data to geotiff=

			The method outlined here requires data in a geotiff format; however, not all data comes in this form. Most GIS utilities provide converters to save data
			in geotiff format. One free and cross platform utility for accomplishing this is the [http://www.gdal.org/gdal_translate.html gdal_translate] command, which
			is part of the Geospatial Data Abstraction Library (GDAL) [http://www.gdal.org/]. Often it is sufficient to run the following command to perform the conversion:
			gdal_translate -of GTiff <source dataset> <destination dataset>
			GDAL command line scripts are also capable of performing reprojection as well as simple processing of nearly any GIS file format.

			=Interpolating data onto a model grid using geogrid=

			Using the original <tt>namelist.wps</tt> used to create the domain. It is relatively simple to rerun geogrid with an additional dataset from
			your source data. In this example, we will use the namelist linked [https://gist.github.com/3696702 here] and the geotiff data at [[File:O9820-B65-P1 fire mask.tif]].
			*Compile WPS as described [[WPS with GeoTIFF support\|here]] to enable geotiff support.
			*Edit the geogrid table at <tt>geogrid/GEOGRID.TBL</tt> to contain the new variable. See the list of table parameters [http://www.mmm.ucar.edu/wrf/users/docs/user_guide_V3.1/users_guide_chap3.htm#_Description_of_GEOGRID.TBL here]. You can remove all of the variables present
			with the exception of <tt>LANDUSEF</tt> to save on computation time. A minimal table is as follows:
			<pre>===============================
			name=LANDUSEF
			priority=1
			dest_type=categorical
			z_dim_name=land_cat
			landmask_water = modis_30s:17 # Calculate a landmask from this field
			landmask_water = modis_lakes:17,21 # Calculate a landmask from this field
			landmask_water = usgs_lakes:16,28 # Calculate a landmask from this field
			landmask_water = default:16 # Calculate a landmask from this field
			dominant=LU_INDEX
			interp_option = modis_30s:nearest_neighbor
			interp_option = 30s:nearest_neighbor
			interp_option = usgs_lakes:nearest_neighbor
			interp_option = modis_lakes:nearest_neighbor
			interp_option = 2m:four_pt
			interp_option = 5m:four_pt
			interp_option = 10m:four_pt
			interp_option = default:four_pt
			rel_path= modis_30s:modis_landuse_20class_30s/
			rel_path= 30s:landuse_30s/
			rel_path= usgs_lakes:landuse_30s_with_lakes/
			rel_path= modis_lakes:modis_landuse_21class_30s/
			rel_path= 2m:landuse_2m/
			rel_path= 5m:landuse_5m/
			rel_path= 10m:landuse_10m/
			rel_path= default:landuse_2m/
			===============================
			name=FIREMASK
			priority=1
			subgrid=yes
			dominant_only=FIREMASK
			dest_type=categorical
			z_dim_name=firecat
			fill_missing = 0.
			interp_option=default:nearest_neighbor
			abs_path=default:./firemask
			===============================</pre>
			*Create a new directory under <tt>WPS</tt> (here we use <tt>firemask</tt>) and copy the geotiff file into this directory.
			*Create an index file in the directory you created. The format of the index file is described [[WPS_with_GeoTIFF_support#Using_GeoTIFF_with_WPS\|here]] and [http://www.mmm.ucar.edu/wrf/users/docs/user_guide_V3.1/users_guide_chap3.htm#_Description_of_index here]. In this example, our index file will contain
			the following
			<pre>geotiff=O9820-B65-P1_fire_mask.tif
			type=categorical
			category_min=1
			category_max=9
			tile_bdr=3</pre>
			*Run <tt>geogrid.exe</tt>

			At this point, the newly interpolated data is in the file <tt>geo_em.d01.nc</tt> under the variable given in the table (here <tt>FIREMASK</tt> in [[File:FIREMASK Geo em.nc.gz]]). The data can be added to a wrfinput or wrfrst file using ncks [http://nco.sourceforge.net/] using the following command:
			ncks -A -v FIREMASK geo_em.d01.nc wrfinput_d01
	[[Category:Howtos\|Ingest heat flux data]]		[[Category:Howtos\|Ingest heat flux data]]

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2012-08-13T14:41:36Z

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[[Category:Howtos|Ingest heat flux data]]

How to ingest heat flux data - Revision history

Jbeezley at 08:12, 11 September 2012

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