SMS:PBL

The PBL engine is developed and maintained by Oceanweather Inc. Distribution of the model itself is controlled by OWI and is not available for sale through Aquaveo.

The storm track in a PBL wind coverage is fed into the PBL model, which then produces output for use in ADCIRC.

To create a PBL Wind coverage, select PBL as the wind model in the coverage attributes. This will enable the Options button for PBL, and change the node attributes dialog.

Coverage Attributes

The options button brings up a dialog with various PBL options. Some of these options affect the pbl_input.inp file, while others affect the header for the *.Trop file. Each option corresponds fairly directly with a line in either file.

• Title 1–6: These are the header lines for the *.Trop file. They are currently printed exactly as entered without any modification.
• Time step: Time step of output in minutes
• Inner nest grid spacing: 2 km is typical
• Boundary layer height: 450m default
• Wind Output and Output Options simply define what data for PBL to output.

Node Attributes

Here are the fields contained in the node attributes dialog for PBL:

• Date – Year, month, day, hour and minute (seconds are ignored)
• Latitude – Latitude in deg
• Longitude – Longitude in deg
• Rotation of solution – Rotation of Solution (deg) typically set to 0, positive values rotate the entire solution clockwise
• Is Snap – Snapshot solutions. Must be checked for the first and last entry, which SMS does for the user.
• Eye Latitude (deg)
• Direction of travel – Direction (to which) the storm is heading (deg), 0=storm heading towards the North, 90=storm heading towards the *East,180=storm heading South, and 270=storm heading towards the West.
• Translational speed – Translational speed of the storm (knots)
• Central pressure – Central/eye pressure (mb)
• Synoptic steering flow (knots)
• Dir of steering flow – Direction (from which) of steering flow (met. deg), 0=winds from the North (wind travels from North to South), 90=winds from *the East,180=winds from the South, 270=winds from the East
• Scale pressure (inner radii) – Scale pressure radius (Nmi) of inner radii
• Scale pressure (outer radii)– Scale pressure radius (Nmi) of outer radii (optional)
• % of RAD1 pressure drop – (0–100) Percent of pressure drop associated with the first radius
• of active profiles – Number of active azimuthally varying B/Pfar profiles (1-4). Each profile has the following fields:
• Azimuth – Azimuth (deg) for this profile #, 0=North Azimuth, 90=East Aximuth, 180=South Aximuth, 270=West Aximuth
• Holland’s B for RAD1 – Holland’s B associated with RAD1 for profile #
• Far Field pressure – Far Field pressure (mb) associated with profile #
• Holland’s B for RAD2 – Holland’s B associated with RAD2 for profile #

Hurricane Data (HURDAT) File

Most of the information mentioned above is contained in the hurdat file that can be download at NOAA website. Make sure to save the Easy to Read version with .hurdat extension. The hurdat file does not contain all the information needed in order for the PBL to run. Data for the Scale Pressure Inner Radii and for the Holland's B for RAD1 will have to be entered manually into the spreadsheet. If data is not easily available, use as follows:

• Scale Pressure Inner Radii – 11
• Holland's B for RAD1 – 1.27

Grid Frames

The PBL coverage requires a grid frame to define some of the pbl_input.inp parameters. When loading this file SMS will create a grid frame, but a user can easily make their own when creating a coverage from scratch. Creating and editing this grid frame is no different from normal in SMS. Only the Angle field isn't used yet (and should be left at 0 for now).

PBL requires a grid frame and associated cell size data. The Create Grid Frame and select Grid Frame tools are used to create the grid frame and to specify cell sizes. Cell sizes are in degrees of latitude and longitude so appropriate values should be entered. Rather than doing Map → 2D grid, SMS launches PBL from the map module and when PBL output files are read into SMS, SMS will create a grid to view the output data.

Exporting and Running PBL

To export the PBL files and run PBL, right-click on the coverage and select one of the options below:

• Export PBL files – Export the pbl_input.inp and *.Trop files. A user will need to save the SMS project before doing this.
• Save Project, Export and Launch PBL – Performs all 3 steps in a row. Saves the SMS project, exports the PBL files, and launches the executable.
• Model Check... – Runs the model check for PBL. This displays the configuration errors and their remedies.
• Launch PBL – Runs PBL in a command prompt in a separate window.

Viewing PBL Wind Output

Any of the grid outputs generated by PBL may be read in and visualized in SMS. If a file is read in and no wind grid exists with the same parameters (location, #cells, etc.), then SMS will create a new grid. Otherwise, SMS will add the new dataset to the existing grid. The files supported by SMS include:

• *.asd – Average boundary layer wind velocity
• *.dbc – Distance and bearing from center
• *.frv – Friction velocity
• *.str – Stress
• *.WND – Wind velocity at 10 m (used by ADCIRC)
• *.pre – Sea level pressure (used by ADCIRC)

Once the outputs are read in the data can be visualized using the standard SMS tools such as contours and vectors.

Additional PBL Output

By toggling the option "WAM input" in the PBL Model Control, the user can tell PBL to write out three additional files as output. The files are:

• fort.12 – wind snaps
• fort.20 – contains the beginning and end dates in YYYYMMDDHHMMSS format
• fort.21 – contains the beginning and end dates in YYYYMMDDHH format

Within SMS, a user can select the fort.12 file to be used as the wind data for a WAM simulation.

Using PBL with ADCIRC

To setup ADCIRC to use wind inputs from PBL, the user specifies the PBL coverage to use in the Wind tab of the ADCIRC model control dialog by clicking on the select coverage button. A user can include a second PBL simulation in order to use two PBL simulations with different grid resolutions. The parameter wind multiplier corresponds to the multiplier in the ADCIRC fort.22 file.