SMS:Generate/Edit Spectra

Generate Spectra dialog

This page describes both the Generate Spectra and Edit Spectra dialogs since they are almost the same dialog. The Generate Spectra dialog is accessed through the Spectral Energy dialog (by pushing the Generate Spectra button). The Edit Spectra dialog is accessed through the Spectral Energy dialog by right-clicking on a grid or spectra in the Spectral Manager and clicking Edit Spectra. SMS creates/edits the spectra when the Generate/Edit button is clicked. All units for the options are feet or meters, depending on the coordinate system. STWAVE runs in metric units, so if the current units are in English units inside SMS, all data is converted to metric when it is saved. The settings are shown below (default values are shown in parenthesis):

Parameter Settings

• Generation Method – Choose the method (TMA (Shallow Water), JONSWAP, Bretschneider (ITTC), Pierson-Moskowitz, or Ochi-Hubble Double Peak) to use to generate the spectra. Each method has slightly different options. JONSWAP and Pierson-Moskowitz both require additional information about what values to use to specify the spectra.
• Replace Old Spectra – Delete all existing spectra in Spectral Energy dialog after the new spectra are generated. Not available when editing.
• Directional Spreading Distribution – Choose to use either the Wrapped Normal distribution or the Cosine Power distribution. With the wrapped normal option, a standard deviation and maximum angle cutoff must be specified. With the cosine power option, the spreading index and the maximum cutoff angle must be specified. The recommended cutoff angle is three times the standard deviation of the directional distribution.
• Gauge Depth – Water depth in meters (d = 5.0). Choose whether to specify once for all spectra or to specify for each spectrum.

Angle Settings

• Projection – The wave direction can be specified in a Oceanographic, Meteorologic, Shore Normal, or Cartesian coordinate system.

Spectral Parameters

The following are used by SpecGen to generate the spectra.

• Time (hrs) – Time offset using the specified units for the spectral node.
• Angle (deg) – Approach angle relative to the shore normal in the clockwise direction measured in degrees (wvang = 25.0).
• Hs (m) – The incident zero moment wave height (hm0 = 1.0).
• Tp (sec) – Wave period in seconds (tp = 20.0).
• Gamma – Spectral peak dispersion factor (igamma = 3.3).
• nn – Number of Nearest Neighbors to be calculated, Directional or peak dispersion factor, must be even integer (inn = 4).
• Gauge Depth (m) – Water depth in meters (d = 5.0). This parameter is available if the Gauge Depth option above is set to Specify for each spectrum.

Spreadsheet Options

• Import/Export – Import/export an ASCII, space delimited text file with the spectral generator parameters. The file format is:

SPECTRAL TABLE	Values
Method Option Time Index Angle Hs(1) Tp(1) Gamma (1) Hs (1) Tp(1) Gamma(1) Hs(2) Tp(2) Gamma(2) Wind Fetch nn StdDev Depth	Headers
0 -1 999.0 None 25.0 1.0 20.0 8.0 999.0 999.0 999.0 999.0 999.0 30.0 999.0 0.001	1st row of values
0 -1 999.0 None 30.0 1.0 16.0 8.0 999.0 999.0 999.0 999.0 999.0 30.0 999.0 0.001	2nd row of values

Additional format description is found in CMS-Wave Spectral Table File.

• Import from GenCade – Imports wave parameters from the Filtered Ocean Conditions dialog. This button is only available if data has been filtered in GenCade.

• Spectral Defaults – This opens a section of the dialog that lists the approximate spectral parameters. Double-click a row of values to replace the selected spreadsheet row(s). The period (T), gamma, and nn will be replaced for the row. If the period in the spreadsheet does not match a period in the table, the spreadsheet period is rounded to the nearest table period.

Related Topics

• Spectral Energy
• Direction Conventions and Conversions