TUFLOW NetCDF Cell Centre Output Format

Introduction

This page contains information on the NetCDF file format used for cell centered model outputs from a TUFLOW simulation. To specify cell centered NetCDF output from TUFLOW, the 2017 version or later must be used and "CC" must be included in the Map Output Data Formats, e.g.
Map Output Format == xmdf cc ! Output both xmdf and Cell Centered NetCDF formats

There are a range of additional NetCDF related commands, to control the output further these are:
NetCDF Output Compression == OFF | {ON} | compression level <0 – 9>
NetCDF Output Start Date == {2000-01-01 00:00} | OFF | <date in isodate format>
NetCDF Output Time Unit == DAY | {HOUR} | MINUTE
NetCDF Output Direction == {ANGLE} | BEARING
NetCDF Output Format == {FEWS} | Generic

Please refer to the TUFLOW Manual for more details on these commands.

Global Attributes

The NetCDF file has four global attributes:

• Title - The simulation name
• Source - The TUFLOW version which has been used
• References - The documentation of the NetCDF file, i.e. this page!
• Comment - A description of the output.
• NetCDF File Format Version - A unique value for file version, for the 2017 version this is 2.
• NetCDF Data Type - This is 1 for "NC" raster output and 2 for cell centered results.

An example of the Global Attributes is:

Global Attributes:
           title      = 'M01_5m_002_NC2'
           source     = 'TUFLOW Build: 2015-12-BB-Dev-iSP-w64'
           references = 'TUFLOW NetCDF Raster Output Format (http://wiki.tuflow.com/index.php?title=TUFLOW_NetCDF_Raster_Output_Format)'
           comment    = 'Contains raster TUFLOW output, TUFLOW netcdf version: 1'

Dimensions

The output NetCDF will have three or four dimensions depending on if the Generic or FEWS format has been specified. These are:

• x - the number of x coordinates (columns of data)
• y - the number of y coordinates (rows of data)
• time - the number of outputs. Note that this is an unlimited dimension meaning that the number of time changes each time a new output is written
• static_time (FEWS Format only) - This has a size of 1 and is used for storing a time for the static data (such as maximums)

An example of the Dimensions is:

Dimensions:
           x           = 1946
           y           = 856
           static_time = 1
           time        = 161   (UNLIMITED)

Variables

All outputs for the simulation are written to a single NetCDF file. These are split into three categories:

• Common variables
• Temporal variables
• Non Temporal variables.

For example if the model writes depths out every 10 minutes and tracking maximums is enabled (default) then two depth datasets are written: depths and maximum_depths. These are described further below.