Gridded Irradiance Output

When parameter 14) Number of cells in X-Y direction in amc.inp is set to a value greater than 0, the AOMC model generates spatially-resolved gridded irradiance data. This output is useful for visualizing the 2D distribution of light when light source is other than collimated.

The format of this gridded output is controlled by parameter 14b) Output to Surfer format.

1. Plain ASCII Matrix Format (surfer = 0)

When the Surfer format option is turned off (0), the model produces four files, each containing data for all simulated wavelengths and depths in a plain ASCII format.

  • grided.out: Gridded Downward Planar Irradiance (\(E_d\))
  • grideu.out: Gridded Upward Planar Irradiance (\(E_u\))
  • gridedo.out: Gridded Downward Scalar Irradiance (\(E_{od}\))
  • grideuo.out: Gridded Upward Scalar Irradiance (\(E_{ou}\))

File Structure

All four grid*.out files share the same structure. They consist of a series of data blocks, where each block represents the spatial distribution of irradiance for a single wavelength at a single depth. The blocks for each wavelength are written sequentially.

The depths at which the grids are generated are determined by the settings for parameter 6) Number of depth recording layers in the amc.inp file. Grids are produced for each of these layers, in addition to a grid just above the water surface (layer index -1) and just below it (layer index 0).

Data Block Structure

Each data block is composed of a header section followed by a data matrix.

Header Section

The header provides metadata for the subsequent grid. It consists of four lines:

  1. Grid and Run Info: Contains the grid dimensions, wavelength, and depth. GRID [N] LAMBDA [wavelength] nm DEPTH [depth] m

    • [N]: The number of cells in the X and Y dimensions.
    • [wavelength]: The wavelength for this grid, in nanometers.
    • [depth]: The depth of the grid, in meters.

  2. X-Axis Extents: The minimum and maximum X coordinates of the grid. XMIN XMAX [min_x] [max_x]

  3. Y-Axis Extents: The minimum and maximum Y coordinates of the grid. YMIN YMAX [min_y] [max_y]

  4. Z-Value Extents: The minimum and maximum irradiance values found within this specific grid. ZMIN ZMAX [min_irradiance] [max_irradiance]

Data Matrix

Immediately following the four-line header is the data matrix. This is an N x N grid of floating-point numbers. Each row in the file corresponds to a row in the spatial grid.

Example

Below is a conceptual example of a single data block for a 5x5 grid in a grided.out file when surfer = 0.

GRID           5 LAMBDA   550.000 nm DEPTH     1.000000 m
XMIN XMAX     -2.500000      2.500000
YMIN YMAX     -2.500000      2.500000
ZMIN ZMAX    1.10000000E-03    8.50000000E-02
 1.10000000E-03  1.50000000E-03  1.80000000E-03  1.50000000E-03  1.10000000E-03
 1.50000000E-03  5.50000000E-02  8.50000000E-02  5.50000000E-02  1.50000000E-03
 1.80000000E-03  8.50000000E-02  1.20000000E-01  8.50000000E-02  1.80000000E-03
 1.50000000E-03  5.50000000E-02  8.50000000E-02  5.50000000E-02  1.50000000E-03
 1.10000000E-03  1.50000000E-03  1.80000000E-03  1.50000000E-03  1.10000000E-03

--- Next data block for a different depth or wavelength would follow ---

2. Surfer ASCII Grid Format (surfer = 1)

When the Surfer format option is turned on (1), the model produces gridded output for Downward Planar Irradiance (\(E_d\)) and Upward Planar Irradiance (\(E_u\)) only.

Instead of appending all data to a single file, the model creates a separate file for each combination of depth and wavelength.

File Naming Convention

The files are named using the pattern [Type]_[Depth]_[Wavelength].grd.

  • [Type]: Eu or Ed.
  • [Depth]: A code representing the depth layer:
    • 0000a_: Above the water surface (layer -1).
    • 0000w_: In the water at the surface (layer 0).
    • [#####]: A zero-padded integer for subsequent depth layers (e.g., 00001_).
  • [Wavelength]: A zero-padded integer representing the wavelength multiplied by 1000.

Example Filenames: * Eu_0000a__450000.grd: Upward planar irradiance, above the surface, for wavelength 450.0 nm. * Ed_00001__675000.grd: Downward planar irradiance, at the first depth layer, for wavelength 675.0 nm.

File Structure

Each .grd file follows the standard Surfer ASCII Grid format, which is compatible with Surfer software from Golden Software and other GIS/visualization tools. The structure is:

  1. Line 1: A 4-character ID DSAA.
  2. Line 2: The number of grid lines along the X and Y axes (Nx Ny).
  3. Line 3: The minimum and maximum X values of the grid (Xmin Xmax).
  4. Line 4: The minimum and maximum Y values of the grid (Ymin Ymax).
  5. Line 5: The minimum and maximum Z (irradiance) values in the grid (Zmin Zmax).
  6. Subsequent Lines: The grid data, written one row at a time, with values for each column in that row separated by spaces.