README for wind turbine drag parameterization schemes, added 20101220.  JM

*Compiling the code.* no different from normal

*Running the code.*  There are new variables added to the phys block of
the namelist.input file.  The string valued variable windturbines_spec
controls the overall operation of the scheme.  If it's set to "none"
(quotes included) the wind turbine scheme is off.  If it's set to
"ideal",  the turbine drag scheme is in idealized mode and other namelist
variables in the block control the geometry and characteristics of the
wind farm.  If it's set to the name of a file in the run directory --
for example, "windspec.in" -- then the scheme is on and the location and
characteristics of each turbine is set individually from the contents of
that file.  Which scheme is active will be controlled by another variable
TBD (not yet implemented, since there's only one scheme right now).

*Idealized configuration.* If windturbines_spec is set to "ideal", the
geometry and characteristics of the farm are controlled by the following
additional variables in the phys block of the namelist.input file:

 name        type     sample description
                      value
 turbgridid  integer   1     id of the WRF domain containing the farm
 hubheight   real     100.   height in meters of all turbine hubs in farm
 diameter    real     100.   diameter in meters of all turbine rotors in farm
 stdthrcoef  real     0.158  standing thrust coefficient of all turbines in farm
 cutinspeed  real     3.5    cut in speed (m/s) of all turbines in farm
 cutoutspeed real     30.    cut out speed (m/s) of all turbines in farm
 power       real     5.0    nominal power (MW) of all turbines in farm
 turbpercell real     1.0    number of turbines per grid cell
 ewfx        integer  10     x-extent of rectangular wind farm in grid cells
 ewfy        integer  10     y-extent of rectangular wind farm in grid cells
 pwfx        integer  45     x-coordinate of grid cell in sw corner of farm
 pwfy        integer  45     y-coordinate of grid cell in sw corner of farm


*Real-world configuration.*  The location and characteristics of each
turbine is specified individually in the file named by the variable
windturbines_spec.  Each line of the file specifies one turbine.
The entries of a line are separated by spaces.  The entries are listed
in order on the line and specify the following, by position on the line:

     1. The WRF grid id into which the turbine is placed [integer]
     2. True latitude of the wind turbine in degrees   [real]
     3. True longitude of the wind turbine in degrees  [real]
     4. Height in meters of the turbine hub [real]
     5. Diameter in meters of the rotor     [real]
     6. Standing thrust coefficient         [real]
     7. Nominal power of turbine (MW)       [real]
     8. Cutin speed (m/s) [real]
     9. Cutout speed (m/s) [real]

The location of each turbine is specified using the lat and lon elements
for the turbine's entry in the windspec file.  That is, the i,j index
in the grid is computed from the true latitude (entry 2) and the true
longitude (entry 3).  The coordinate in the j dimension is computed by
checking true latitude against the LAT_V field in the wrfinput initial
conditions file.  The i dimension is computed by checking the true
longitude against LONG_U field in the wrfinput file.

*Pseudo-real configuration.*  This mode is only for testing the real-world
specification mechanism.  The contents of the windspec.in file in the
em_seabreeze2d_x directory contains a specification that is identical
to the ideal specification shown above.  However, instead of true
latitude and true longitude, elements 2 and 3 of each entry specify
the i,j grid coordinates of the turbine.  The code knows to treat
these as grid coordinates instead of latitude and longitude because
for idealized WRF cases, the LAT and LONG fields in wrfinput files are
set to all zero.  When the model reads a wrfinput file for an idealized
case, it checks to see if the lat and lon fields of the case have data
in them or if they are just zeros.  If they do not have data in them
(just have zeros) fields 2 and 3 of the windspec file are treated as i,j
coordinates are used.  A sample windspec file for a pseudo-real run is
in test/em_seabreeze2d_x/windspec.in).

*Specific note for the Fitch scheme.*  The Fitch scheme is based on
Blahak et al, 2010, of Wetter Jetzt GbR.  The specific implementation
comes from Anna Fitch, Alok Gupta, and Idar Barstad at Uni Bergen,
Norway.  It was added to this release of WRF by Jimy Dudhia, Joe Olson
(NOAA), Julie Lundquist (U. Colorado/NREL), and John Michalakes (NREL).
It works with the MYNN PBL and modifies the QKE field representing 2xTKE
to include the TKE produced by wind turbines. QKE is advected as a part
of the scalar 4D tracer array in WRF.