Changes between Version 23 and Version 24 of HYCOM

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Timestamp:
10/02/09 18:00:44 (4 years ago)
Author:
jjr8
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  • HYCOM

    v23 v24  
    8989    * [http://code.env.duke.edu/projects/mget/browser/WikiFiles/Examples/HYCOM/ascii2shp.exe?format=raw ascii2shp.exe] - Helper program for rapidly converting a CSV file into a shapefile. '''Warning:''' be sure to save this with a {{{.exe}}} extension (some browsers may try to prevent it). 
    9090 
    91  3. Using your favorite web browser or FTP client, go to the HYCOM server and navigate to the directory containing the files for the HYCOM dataset you want. From the '''topo''' directory on the HYCOM server, download the files '''regional.grid.a''' and '''regional.grid.b''' and save them to '''C:\HYCOM'''. 
     91 3. Using your favorite web browser or FTP client, go to the HYCOM server and navigate to the directory containing the files for the HYCOM dataset you want. For this example, I used the [http://www.hycom.org/dataserver/glb-simulation/expt-05pt8 HYCOM Global 1/12° Simulation (expt_05.8)] which had files available by FTP [ftp://ftp.hycom.org/datasets/GLBa0.08/expt_05.8 here], but you should study the different datasets that are available and choose the one that best fits your needs. Remember that the script I wrote for this procedure only works with global HYCOM datasets. (If you have some programming skills, you could probably modify it to work with regional datasets.) 
     92 
     93 4. On the HYCOM server, go to the '''topo''' directory, download the files '''regional.grid.a''' and '''regional.grid.b''', and save them to '''C:\HYCOM'''. 
    9294 
    9395 4. Create the directory '''C:\HYCOM\NetCDFs'''. 
    9496 
    95  5. From the HYCOM server, go to the '''data''' directory and then to the subdirectory for your oceanographic variable of interest, either '''salt''', '''temp''', '''u''', or '''v'''. Download the netCDF files ({{{.nc}}} file extension) for your dates of interest. If you are downloading a lot of files and have a fast Internet connection, consider using a program like SmartFTP that can download multiple files simultaneously, to work around the per-file throughput limitation imposed by the server. (I was told by Michael !McDonald of HYCOM that this is ok.) 
     97 5. On the HYCOM server, go to the '''data''' directory and then to the subdirectory for your oceanographic variable of interest, either '''salt''', '''temp''', '''u''', or '''v'''. Download the netCDF files ({{{.nc}}} file extension) for your dates of interest. If you are downloading a lot of files and have a fast Internet connection, consider using a program like SmartFTP that can download multiple files simultaneously, to work around the per-file throughput limitation imposed by the server. (I was told by Michael !McDonald of HYCOM that this is ok.) 
    9698 
    9799 6. Create the directory '''C:\HYCOM\Rasters'''. 
    … …  
    132134    }}} 
    133135 
    134  9. Examine the '''C:\HYCOM\Rasters''' directory. It should look something like the example below, but not be as fully populated. I show a fully populated one here so you'll get a better idea what it will look like after you extract more data. [[BR]][[BR]] Within '''C:\HYCOM\Rasters''' is one subdirectory for each netCDF variable that you have extracted. With the steps above, only the '''temperature''' subdirectory will be created. The example below shows all four: '''salinity''', '''temperature''', '''u''', and '''v'''. [[BR]][[BR]] Within each variable subdirectory are three subdirectories: '''Antarctic''', '''Arctic''', and '''Equatorial'''. These hold rasters for the three sections of the HYCOM grid. Each time you extract a depth layer for a given variable from a given file, one raster will be written to each of these subdirectories. [[BR]][[BR]] Within those are subdirectories specifying the depth. '''Depth_0''' is the surface layer, '''Depth_100''' is the 100 m depth layer, and so on. With the steps above, only '''Depth_0''' will be created. The example below shows four depth layers. [[BR]][[BR]] Within the depth directories are year subdirectories. The steps above will produce one year (2003), while the example below shows two years. [[BR]][[BR]] The year directories contain rasters. Each raster name begins with an abbreviation for the variable (either salt, temp, u, or v) followed by the four-digit year, followed by the three-digit day of the year, followed by a one-digit code indicating the region (1 - Arctic, 2 - Equatorial, 3 - Antarctic). The steps above will create one raster in each year directory (temp2003292*) while the example below shows two rasters. The rasters are stored in ERDAS Imagine format (.img format). If you prefer another format such as !ArcInfo Binary Grid or GeoTIFF, you can edit the script to produce that format. 
     136 9. Examine the '''C:\HYCOM\Rasters''' directory. It should look like the example below, but not be as fully populated. I show a more populated one here so you'll get a better idea what it will look like after you extract more data. [[BR]][[BR]] Within '''C:\HYCOM\Rasters''' is one subdirectory for each netCDF variable that you have extracted. With the steps above, only the '''temperature''' subdirectory will be created. The example below shows all four: '''salinity''', '''temperature''', '''u''', and '''v'''. [[BR]][[BR]] Within each variable subdirectory are three subdirectories: '''Antarctic''', '''Arctic''', and '''Equatorial'''. These hold rasters for the three sections of the HYCOM grid. Each time you extract a depth layer for a given variable from a given file, one raster will be written to each of these subdirectories. [[BR]][[BR]] Within those are subdirectories specifying the depth. '''Depth_0''' is the surface layer, '''Depth_100''' is the 100 m depth layer, and so on. With the steps above, only '''Depth_0''' will be created. The example below shows four depth layers. [[BR]][[BR]] Within the depth directories are year subdirectories. The steps above will produce one year (2003), while the example below shows two years. [[BR]][[BR]] The year directories contain rasters. Each raster name begins with an abbreviation for the variable (either salt, temp, u, or v) followed by the four-digit year, followed by the three-digit day of the year, followed by a one-digit code indicating the region (1 - Arctic, 2 - Equatorial, 3 - Antarctic). The steps above will create one raster in each year directory (temp2003292*) while the example below shows two rasters. The rasters are stored in ERDAS Imagine format (.img format). If you prefer another format such as !ArcInfo Binary Grid or GeoTIFF, you can edit the script to produce that format. 
    135137 
    136138    [[Image(source:/WikiFiles/Examples/HYCOM/Output_Directories.png)]] 
    137139 
    138140'''TO BE CONTINUED...''' 
     141 
     142== Important notes == 
     143 
     144 * The HYCOM '''u''' variable provides the water velocity in the east/west direction, with east being positive. The '''v''' variable provides water velocity in the north/south direction, with north being positive. On the Mercator rasters, east is to the left and north is up. But on the polar stereographic rasters, east is either clockwise around the center of the image (Arctic) or anti-clockwise (Antarctic), while north is either towards the center of the image (Arctic) or away from it (Antarctic). If you use a tool to produce a quiver plot of the current vectors for the polar rasters, the tool must be smart enough to understand this. The tool that I have privately provided to people in the past for creating vector shapefiles does not understand this.