CMS-Flow Wind Forcing

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There are two types of atmospheric forcing in CMS; spatially constant (Wind Curve) and spatially variable. Currently, only the spatially constant option is supported through the SMS interface. In order to specify spatially variable winds and atmospheric pressure, it is necessary to use the Advanced Cards section of the *.cmcards file.

Wind Parameters

The wind parameters are the wind drag scale factor and the anemometer height. The wind drag scale factor directly multiples by the wind shear stresses.

Table 1. CMS-Flow cards for the wind drag scale factor and anemometer height.

Card Arguments Default Description
WIND_DRAG_SCALE_FACTOR REAL 1.0 Scaling factor for wind shear stresses
ANEMOMETER_HEIGHT REAL 10.0 Height of wind speeds in meters
  • Notes:
1. The wind drag scale factor is only intended for testing, and should NOT be used for calibration purposes.
2. The wind shear stresses and pressure gradients are multiplied by the ramp function before they are used in the model.

Wind Curve

SMS 10.1
SMS 10.1

Temporally varying, spatially constant winds are input in CMS in the Wind Section of the CMS-Flow Model Control Window. To add wind forcing to a current CMS-Flow project click on CMS-Flow | Model Control and then on the Wind/Wave tab. Activate wind forcing by clicking on the Include Wind check box. Winds may be imported using an *.m2w file or by specifying a curve for wind speed and direction. To specify a curve for each click on the respective box which says Curve undefined which will open the XY Series Editor. The time series may be manually entered, copied or imported from an *.xys file in the XY Series Editor.

CMS-Flow cards related to wind

Card Arguments Format Description
WIND_INPUT_CURVE CHARACTER CHARACTER <Grid File> <Dataset Path> Name of model parameter file followed wind curve path


Spatially Variable Wind and Atmospheric Pressure

CMS-Flow V4.0 and higher have the option to use spatially variable wind and atmospheric pressure forcing. Currently, this feature is specified in the advanced card section. There are two file format types currently accepted in CMS for spatially variable winds and atmospheric pressure.

  • Notes:
Interpolation File: When using spatially variable winds CMS V4.0 will output a file named Intpcoef_wndfl.bin. This file contains the coefficients used to interpolate the winds and atmospheric pressure to the CMS-Flow grid. If the same flow and wind grids are run, the model will automatically detect the interpolation file and read in the coefficients instead of calculating them. If the either grid is changed in size, the model will automatically detect this and recalculate the coefficients. However, if the grids are changed but stay the same size, the model will not be able to detect that they have changed. Therefore, whenever any changes are made to the flow or wind grids, it is best to delete the interpolation file.
Ramp Period: During the ramp period, the ramp is applied to both the wind shear stresses and spatial variations of the atmospheric pressure.

Three types of Spatialy Variable Wind formats are presently accepted. Each discussed briefly below

Wind Speed and Direction (Navy Fleet) Format

This file format is equivalent to the ADCIRC fort.22 format with NWS=3.

For this format, the wind speed and direction information are specified on a rectangular grid in the same coordinate system and projection as the CMS. The grid is assumed to vary from north to south and west to east so that north-west corner is the grid origin. The spatial extents of the wind grid must be consistent with the flow grid.

Table 2. CMS-Flow cards related to the single wind or wind and atmospheric pressure input file.

Card Arguments Type Description
WIND_FLEET_FILE <File Name> CHARACTER Name wind single input file including path if different from CMS-Flow input files. Uses US Navy Fleet Format described below. Same as ADCIRC NWS=3.
WIND_GRID_PARAMETERS NWY, NWX, MaxY, MinX, DY, DX NWY and NWX are INTEGER.
All others are REAL
Specifies wind grid on the same projection as CMS. Coordinates and increments are specified in meters.


Notes:

  1. NWY and NWX - number of values in Y and X direction, respectively.
  2. MaxY and MinX - maximum Y value and minimum X location value, respectively.
  3. DY and DX - Distance in meters from value to value in field.
  4. Wind Speed must be in m/s.
  5. Wind direction is the direction the wind blows from and must be in degrees.

FORTRAN Code

WIND_FLEET_FILE - An excerpt of the FORTRAN code used to read the a single Navy Fleet wind time step is shown below:

read(wunit,*) iwtime !=year*1000000+month*10000+day*100+hour
do i=1,nwindi
 do j=1,nwindj
   read(wunit,*) wndspd(i,j)  
 enddo
enddo 
do i=1,nwindi
 do j=1,nwindj
   read(wunit,*) wnddir(i,j)  
 enddo
enddo 

Wind Velocity (component) and Pressure Format

This file format is equivalent to the ADCIRC fort.22 format with NWS=6.

  • For a field of wind velocities (U/V components) with pressure, the ADCIRC NWS=6 type format can be used.
  • Additionally, if no information is available on the atmospheric pressure, specify a constant value for the pressure.

For this formats, the wind and pressure information are specified on a rectangular grid in the same coordinate system and projection as the CMS. The grid is assumed to vary from north to south and west to east so that north-west corner is the grid origin. The spatial extents of the wind/pressure grid must be consistent with the flow grid.

Table 3. CMS-Flow cards related to the single wind or wind and atmospheric pressure input file.

Card Arguments Type Description
WIND_AND_PRESSURE_FILE <File Name> CHARACTER Name wind and atmospheric pressure single input file including path if different from CMS-Flow input files. Same as ADCIRC NWS=6.
1WIND_PRESSURE_SINGLE_FILE <File Name> CHARACTER Name wind and atmospheric pressure single input file including path if different from CMS-Flow input files. Same as ADCIRC NWS=6.
WIND_GRID_PARAMETERS NWY, NWX, MaxY, MinX, DY, DX NWY and NWX are INTEGER.
All others are REAL
Specifies wind grid on the same projection as CMS. Coordinates and increments are specified in meters.
WIND_TIME_INCREMENT wTimeInc REAL Wind time increment in seconds

1 Former name of card. Will remain in Code for backward compatibility.


Notes:

  1. NWY and NWX - number of values in Y and X direction, respectively.
  2. MaxY and MinX - maximum Y value and minimum X location value, respectively.
  3. DY and DX - Distance in meters from value to value in field.
  4. Wind Component Velocity must be in m/s.
  5. Atmospheric pressure must be in Pascals.

An example except from an ASCII wind and pressure input file is shown below.

-3.3572406e-001      5.9331598e+000      1.0037000e+005    
-3.3572406e-001      5.9331598e+000      1.0037000e+005    
 1.7701815e-001      5.7988701e+000      1.0067000e+005    
 1.9533037e-001      5.7927661e+000      1.0097000e+005    
 6.7144811e-001      5.6981530e+000      1.0107000e+005
…

  • Notes:
  1. If no information is available on the atmospheric pressure, than a constant value should be specified for the atmospheric pressure. The constant value does not matter for the hydrodynamics because only the gradients of the pressure field are used to drive the circulation.

FORTRAN Code

WIND_AND_PRESSURE_FILE - An excerpt of the FORTRAN code used to read the a single wind time step is shown below:

do i=1,nwindi
 do j=1,nwindj
   read(wunit,*,end=44,err=22) wndspdx2(i,j),wndspdy2(i,j),atmpres2(i,j)  
 enddo
enddo 

Oceanweather Format

Oceanweather is a consulting company which does wind and wave hindcasting and forecasting. The Oceanweather wind format consists of three ASCII files with wind, atmospheric pressure in

Table 4. CMS-Flow cards related to the Oceanweather input files.

Card Arguments Type Description
OCEANWEATHER_WIND_FILE <File Name> CHARACTER Name of Oceanweather, Inc. wind file (*.win)
OCEANWEATHER_PRES_FILE <File Name> CHARACTER Name of Oceanweather, Inc. pressure file (*.pre)
OCEANWEATHER_XY_FILE <File Name> CHARACTER Name of Oceanweather, Inc. coordinate file (*.xy)

Oceanweather Wind File

The file format for the Oceanweather wind file (*.win) is best described with an example:

Oceanweather WIN/PRE Format                            2008090912      2008091406
iLat= 118iLong=  201DX=0.0150DY=0.0150SWLat=28.50000SWLon=-96.0000DT=200809091200
-4.8891   -4.8873   -4.8855   -4.8838   -4.8821   -4.8805   -4.8789    -4.8774
-4.8759   -4.8744   -4.8730   -4.8717   -4.8704    -4.8692   -4.8680   -4.8669
...
-2.1530   -2.1382    -2.1233   -2.1085   -2.0937   -2.0788   -2.0637   -2.0486
-2.0335   -2.0184   -2.0035   -1.9887   -1.9741   -1.9598   -1.9458    -1.9322
-1.9190   -1.9062   -1.8938   -1.8820   -1.8707    -1.8600
iLat= 118iLong=  201DX=0.0150DY=0.0150SWLat=28.50000SWLon=-96.0000DT=200809091215
-4.9107   -4.9090   -4.9074   -4.9058   -4.9043   -4.9028   -4.9014   -4.9001
-4.8988   -4.8975   -4.8963   -4.8952   -4.8942    -4.8932   -4.8923   -4.8914
-4.8906   -4.8898   -4.8889    -4.8881   -4.8873   -4.8866   -4.8860   -4.8854
...

The last two arguments of the header is are the starting and end times in yyyymmddhh. The wind data is preceded by a header line with the grid information. iLat and iLong are latitude North and longitude West. DX and DY are the grid spacing in units of degrees. SWLat and SWLon are the coordinates of the south-west grid point. DT is the actual time in yyyymmddhhMM. First the wind velocities in the x-direction are read than the velocities in the y-direction. The wind speeds are written in m/s.

FORTRAN Code

An excerpt of the FORTRAN code used to read the file is shown below:

open(nunit,file=windfile,status='old')
read(nunit,*)   !skip  header 
11 format(t6,i4,t16,i4)
read(nunit,11) nwindi,  nwindj
backspace(nunit)
 !... 
13  format(68x,I4,4(I2)) 
read(nunit,13,end=333,err=333)  iyear,imonth,iday,ihour,imin
!... 
12  format(8f10.0)   
read(nunit,12,end=333,err=333)  ((wndspdx(i,j),j=1,nwindj),i=1,nwindi)
read(nunit,12,end=333,err=333) ((wndspdy(i,j),j=1,nwindj),i=1,nwindi)
!... 
333 close(nunit)

Oceanweather Pressure File

The file format for the Oceanweather pressure file (*.pre) is best described with an example:

Oceanweather WIN/PRE Format                            2008090912      2008091406
iLat= 118iLong=  201DX=0.0150DY=0.0150SWLat=28.50000SWLon=-96.0000DT=200809091200
1012.8565 1012.8564 1012.8563 1012.8563 1012.8563 1012.8563 1012.8563 1012.8564
1012.8565 1012.8566 1012.8568 1012.8569 1012.8572  1012.8574 1012.8577 1012.8580
1012.8583 1012.8587 1012.8591  1012.8596 1012.8600 1012.8605 1012.8610 1012.8616
...
1014.2051 1014.2062 1014.2073 1014.2084 1014.2096 1014.2107 1014.2119  1014.2130
1014.2141 1014.2152 1014.2164 1014.2175 1014.2186  1014.2197
iLat= 118iLong=  201DX=0.0150DY=0.0150SWLat=28.50000SWLon=-96.0000DT=200809091215 
1012.9089 1012.9089 1012.9089 1012.9089 1012.9090 1012.9091 1012.9092 1012.9094
1012.9095 1012.9098 1012.9100 1012.9103 1012.9106  1012.9109 1012.9113 1012.9117
1012.9120 1012.9125 1012.9130  1012.9135 1012.9140 1012.9146 1012.9152 1012.9158
...

  • Notes:
  1. The last two arguments of the header is are the starting and end times in yyyymmddhh.
  2. The atmospheric pressure data (in units of mbar) is preceded by a header line with the grid information.
  3. iLat and iLong are latitude North and longitude West.
  4. DX and DY are the grid spacing in units of degrees.
  5. SWLat and SWLon are the coordinates of the south-west grid point.
  6. DT is the actual time in yyyymmddhhMM.

Oceanweather XY File

The file format for the Oceanweather coordinate file (*.xy) should the contain the coordinates of the Oceanweather grid in the same coordinate system as the CMS-Flow grid. The order of the points should be from the south-west corner along each row. A small fortran program is provided hereconverts the Oceanweather grid information to an *.xy file.

903301.20526 77626.22617
904769.21902 77663.98766
906237.22790 77701.93744
907705.23188 77740.07550
909173.23093 77778.40184
910641.22504 77816.91646
...

  • Notes:
  1. The first column is the horizontal coordinate, and the second is the vertical coordinate.

Wind and Atmospheric Pressure Output

In some cases, it is useful to output the wind fields and atmospheric pressure on the flow grid for either post-processing are for checking the input wind fields. The wind speed vectors and magnitude are output in m/s if the following card is specified described in the table below.

Table 5. Other CMS-Flow cards related to wind

Card Arguments Type
WIND_OUT_TIMES_LIST Id number of output times list integer

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