FUNCTION N_VisintIfc_X(r_stateOut, r_stateIn, r_derivOut, r_derivIn, 
r_extrapGuideDown, r_extrapGuideUp, m_slStateValue, m_slFluxGradient, 
n_numExtArraysIn, n_numExtArraysOut, r_ExtArraysIn, r_ExtArraysOut)

real, dimension(:,:,:), intent(out) :: r_stateOut
real, dimension(:,:,:), intent(in)  :: r_stateIn
real, dimension(:,:,:), intent(out) :: r_derivOut
real, dimension(:,:,:), intent(in)  :: r_derivIn
real, intent(in) :: r_extrapGuideDown, r_extrapGuideUp
external m_slStateValue
external m_slFluxGradient
integer, intent(in) :: n_numExtArraysIn
integer, intent(in) :: n_numExtArraysOut
real, dimension(:,:, n_numExtArraysIn), intent(in)  :: r_ExtArraysIn
real, dimension(:,:, n_numExtArraysOut), intent(out) :: r_ExtArraysOut
DESCRIPTION 
Perform the selected interpolation and extrapolation.  The function name represents 
Scalar INTerpolation, following the syntax of ezsint.  However, it can also perform
vector extrapolation.

In the case where the extrapolation has been set to surface or surfacewind, the 
physics of the extrapolation determines what is the gradient of the field at the top 
of the surface layer.  For this reason, if cubicwithderivs or cubiclagrange 
interpolation has been chosen (along with surface or surfacewind extrapolation), the 
layer just above the surface layer is treated specially:  with either of those 
interpolation types, cubicwithderivs interpolation is applied in that layer, using the 
gradient implied by the physics at the top of the surface layer, and the supplied 
gradient at the next boundary or a calculated gradient if necessary.


N.B.:  It must be noted that the routines passed as arguments must presume that
       the location of each vertical level is given as z (meters above the Earth's
       surface).  These are the values supplied in r_ExtArraysIn.  NOTE that
       this implies that the values of r_stateIn are ignored for surface or
       surfacewind extrapolation; in this case they are used only for the interpolation.

       Furthermore, those same routines presume that the lowest level represents the
       Earth's surface.  The r_stateIn values given for that level should be true
       values and not those given by the model (GEM).  [In the case of 'surfacewind'
       extrapolation, the routine supplied probably ignores the r_stateIn values at
       the surface and presumes them to be zero.]

Author: Jeff Blezius - Sept 2002
ARGUMENTS

Input: dimensions are as defined in N_ViqkdefIfc and N_VidefsetIfc
r_stateIn	input array of the state
r_derivIn	input array of the derivative
r_extrapGuideDown	value used for extrapolating below the values of the source grid (set in N_VidefsetIfc) The meaning of these values depends on the selected extrapolation method.
r_extrapGuideUp	value used for extrapolating above the values of the source grid (set in N_VidefsetIfc) The meaning of these values depends on the selected extrapolation method.
m_slStateValue	subroutine to calculate the normalized state value at one vertical level within the surface layer. ('Surface layer' is comprised of the space between the Earth's surface and the first model level above it.) The routine supplied here is usually slfun_tq or slfun_uv from the physical library. Click on the parameter name for a description of its own parameters.
m_slFluxGradientScalar m_slFluxGradientVector	subroutine to calculate the normalized flux at the surface, and the gradient with respect to z, at the top of the surface layer. The routine supplied here is usually sltop_tq or sltop_uv from the physical library. Click on the parameter name for a description of its own parameters; note that the parameters are different depending on whether this is a scalar or a vector calculation.
n_numExtArraysIn	the number of arrays that are being passed in the ExtArraysIn variable; i.e. the third dimension of ExtArraysIn. VALUE USE 0 none of the below kDestDim* + kSrcDim** for surface extrapolation kDestDim* + 3 x kSrcDim** for surface extrapolation of a vector (i.e. wind)
n_numExtArraysOut	the number of arrays that are being passed in the ExtArraysOut variable; i.e. the third dimension of ExtArraysOut. VALUE USE 0 none of the below 0 for surface extrapolation 2 x kDestDim* for surface extrapolation of a vector (i.e. wind)
r_ExtArraysIn(:,:, numExtArraysIn)	extension to this interface to accommodate more input arrays, where the significance of the array is determined according to the third index of ExtArraysIn: LOWER INDEX UPPER INDEX SIGNIFICANCE 1 kDestDim* zDest, height with respect to the surface, in m, of the sought point kDestDim*+1 kDestDim* + kSrcDim** zSrc, height with respect to the surface, in m, of the source point. These values are used only in the surface layer and, if cubicwithderivs or cubiclagrange interpolation is chosen, the input values two levels higher. kDestDim* + kSrcDim**+1 kDestDim* + 2 x kSrcDim** r_y_stateIn, y-component of r_stateIn kDestDim* + 2 x kSrcDim**+1 kDestDim* + 3 x kSrcDim** r_y_derivIn, y-component of r_derivIn
Output:
N_VisintIfc_X	error indication: 0 means 'no error'; see $ARMNLIB/include/ViConstants_f90.h for the significance of other values
r_stateOut	output array of the state
r_derivOut	output array of the derivative
ExtArraysOut(:,:,0)	extension to this interface to accommodate more output arrays, where the significance of the array is determined according to the third index of ExtArraysOut: LOWER INDEX UPPER INDEX SIGNIFICANCE 1 kDestDim* r_y_stateOut, y-component of r_stateOut kDestDim* + 1 2 x kDestDim* r_y_derivOut, y-component of r_derivOut

^*N_kDestDim - the value that was given as N_numVLevels in the T_VerticalGridIfc (from N_ViqkdefIfc) that was passed to VidefsetIfc_X as o_vGridDestnIfc
^**N_kSrcDim - the value that was given as N_numVLevels in the T_VerticalGridIfc (from N_ViqkdefIfc) that was passed to VidefsetIfc_X as o_o_vGridSourceIfc

SEE ALSO