CMS-Wave Spectra File

There are several instances where spectral energy files are used. They all use a similar format, shown below.

30 35  ##  ##.#
0.040 0.050 0.060 0.070 0.080 0.090 0.100 0.110
0.120 0.130 0.140 0.150 0.160 0.170 0.180 0.190
0.200 0.210 0.220 0.230 0.240 0.250 0.260 0.270
0.280 0.290 0.300 0.310 0.320 0.330
202201010000  5.00  10.00  0.130  0.500
0.00000 0.00000 0.00000 0.00000 0.00000 0.00000
0.00000 0.00000 0.00000 0.00000 0.00000 0.00000
0.00000 0.00000 0.00000 0.02000 0.13000 0.25000
... 

---

The first line contains:

• The number of frequency bins (30 in this example)
• The number of direction bins (35)

Depending on if the input file is for a nested grid you may have two more values listed.

• The nested grid number
• The azimuth of the corresponding nested grid.

The next few lines contain frequency values for the grid starting from the smallest and working to the largest frequency. In this example, there are 30 total values starting at 0.040 and incrementing by 0.01 to the largest value of 0.330.

---

The remaining set of lines are a number of records each containing a line with some information for each record followed by several lines of energy density values for each cell in the spectral grid (in this case 30x35 cells)

202201010000  5.00  10.00  0.130  0.500
0.00000 0.00000 0.00000 0.00000 0.00000 0.00000
0.00000 0.00000 0.00000 0.00000 0.00000 0.00000
0.00000 0.00000 0.00000 0.02000 0.13000 0.25000
... 

There are either 5 or 8 values in the first line of each of 1 or more records. There will be 5 values for normal spectra and 8 values when the spectra is coming from a nested grid cell.

The first 5 values are:

• Time/index identifier in one of three formats shown below:
  • ### - unformatted unique index number
  • YYMMDDHH - Year, Month, Day, Hour
  • YYYYMMDDHHNN - Year, Month, Day, Hour, Minutes
• Wind Speed in $m/sec$ (5.0 m/sec in this example)
• Wind Direction in degrees (10.00 degrees)
• Spectral peak frequency (0.13 Hz)
• Tidal offset (0.5 m)

The last 3 values for nested grids (not shown) are:

• Global coordinate of X position of nesting cell
• Global coordinate of Y position of nesting cell
• Significant wave height

Back to CMS-Wave File Formats