According to the Unidata website the Network Common Data Form (NetCDF) software was originally intended to create, access, and share array-oriented data in a form that is self-describing and portable. These deal with a variety of data types that encompass single-point observations, time series, regularly-spaced grids, and satellite or radar images.
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EFDC+ can currently write the native output in NetCDF-CF format for Windows and Linux. EFDC_Explorer (the pre-and post-processor for EFDC+) can also convert the binary files output by EFDC+ (*.OUT) to netCDF.nc files, including the derived water quality parameters. EFDC+ currently exports 44 parameters to NetCDF format. This allows EFDC+ output to be read and displayed on web servers.
EFDC+ exports the NetCDF files at the same interval that it produces the model linkages files, which is set in the tab for Timing and Linkage | Linkage | NetCDF.
The main configuration for NetCDF output is in the EFDC_Exlporer Linkage | NetCDF tabs as shown in Figure 1 240419309. Here the user can turn on netCDF output by checking the Output to NetCDF checkbox. The user may select the level at which the NetCDF data is compressed with the Deflate Level setting. This can range from 1, no compression, to 9 for maximum compression, but is recommended by Unidata to be set to 2 for the best balance between file size and speed.
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Displaying NetCDF Output
There are a number of options available to the user for displaying netCDF output such as using ArcGIS, or using web-based tools such as ncWMS. Some of these are outlined here to help the user to become familiar with these tools.
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) Convert to Text
To convert the .nc file to s a text file, the user can download the ncdump.exe tool and follow step-by-step instruction instructions in Unidata.
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2) Using ArcMap
A detailed guidance video for visualizing NetCDF output using ArcMap has been prepared by DSI and made available here: https://www.youtube.com/watch?v=vgT7dN4UK44
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Figure 2. ArcGIS reading the NetCDF file.
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3) Using NCWMS
ncWMS is a Web Map Service for geospatial data that are stored in CF-compliant NetCDF files. The intention is to create a WMS that requires minimal configuration: the source data files should already contain most of the necessary metadata. ncWMS is developed and maintained by the Reading e-Science Centre at the University of Reading, UK. The latest version is 1.3, released in August 2014.
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ncWMS loads native netCDF files and displays them on a web browser. To make the output the same as EE10 would require further adjustment to the tool. For the purposes of this demonstration, the basic display of the output is shown in the next section.
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4) Using Ocean Data View
Ocean Data View (ODV) is a software package for the interactive exploration, analysis, and visualization of oceanographic and other geo-referenced profile, time-series, trajectory, or sequence data.
ODV supports the netCDF format and lets you explore and visualize CF, COARDS, GDT, and CDC compliant netCDF datasets. This works with netCDF files on your local machine as well as with remote netCDF files served by an OPeNDAP server.
5) Using Python script
Python script can be used to read the netCDF output of the model. For example, a model with 1000 horizontal grids, 5 layers, and the model simulated with 1
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-hour output frequency for 10 days. So each day will have 25-time steps → there are 1000*5*(24*10 + 1) = 1,205,000 lines totally. In which of the total lines, there are lines with NaN values (dry cells), they should be removed. The User can contact us to get the script.
Examples of Model Output
To demonstrate the netCDF output is consistent with the data viewed in EE, a number of comparisons have been made for different models. Examples of an output from the West Lake WQ model in EE, ArcGIS, and ncWMS are shown in Figure 3, Figure 4 and Figure 5 respectively. Note that the West Lake model may be downloaded from the EE website.
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