geo Module Reference

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Module provides geographic interpolation procedures Various functions used for spatial interpolation from low-res forcing grid to high-res model grid. More...

Public Member Functions
subroutine, public	geo_lut (hi, lo)
	Compute the geographic look up table from LOw resolution grid to HIgh resolution grid More...
subroutine, public	geo_interp (fieldout, fieldin, geolut, boundary_only)
	Interpolate fieldout to fieldin using geolut. if boundary_only is true, call boundary_interpolate instead loops over y,z,x but geolut is only defined over x,y (for now) More...
subroutine, public	geo_interp2d (fieldout, fieldin, geolut)
	Interpolate fieldout to fieldin using geolut. More...

Private Member Functions
real function, dimension(4)	bilin_weights (yi, y, xi, x)
	Calculate the weights to use for bilinear interpolation between surrounding points x, y to position xi,yi More...
integer function	minxw (xw, longrid, xpos, ypos, lon)
	Find the minimum next step size in the x direction xw=minxw(xw,lolon,xc,yc,lon) More...
integer function	minyw (yw, latgrid, xpos, ypos, lat)
	Find the minimum next step size in the y direction yw = minyw(yw,lolat,xc,yc,lat) More...
type(position) function	find_location (lo, lat, lon, lastpos)
	Find a location lat,lon in lolat,lon grids Assumes that the lat/lon grids are semi-regular (dx/dy aren't constant but they are nearly so) Calculates dx/dy at the middle of the lat/lon grids, then calculates the location of lat,lon input point using those coordinates. Next proceeds to calculate a new position based on the dx/dy at that position until the new position is within 1 gridcell of the current position Once that "within 1" position is found, search all cells in a 3x3 grid for the minimum distance return a position datatype that includes the found x/y location More...
type(fourpos) function	find_surrounding (lo, lat, lon, pos, nx, ny)
	Given a closest position, return the 4 points surrounding the lat/lon position in lolat/lon More...
subroutine	boundary_interpolate (fieldout, fieldin, geolut)
	Interpolate boundaries of fieldout to fieldin using geolut More...

Detailed Description

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Module provides geographic interpolation procedures Various functions used for spatial interpolation from low-res forcing grid to high-res model grid.

  Entry points: 
      geo_LUT     : creates a geographic look uptable to convert one
                    grid to another
      geo_interp  : interpolates from one grid to another and
                    loops over the third dimension
      geo_interp2d: interpolates from one grid to another
 

Author

Ethan Gutmann (gutma.nosp@m.nn@u.nosp@m.car.e.nosp@m.du)

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Member Function/Subroutine Documentation

real function, dimension(4) geo::bilin_weights ( real, intent(in)  yi, real, dimension(0:3), intent(in)  y, real, intent(in)  xi, real, dimension(0:3), intent(in)  x  )

private

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Calculate the weights to use for bilinear interpolation between surrounding points x, y to position xi,yi

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subroutine geo::boundary_interpolate ( real, dimension(:,:,:), intent(inout)  fieldout, real, dimension(:,:,:), intent(in)  fieldin, type(geo_look_up_table), intent(in)  geolut  )

private

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Interpolate boundaries of fieldout to fieldin using geolut

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type(position) function geo::find_location ( class(interpolable_type), intent(inout)  lo, real, intent(in)  lat, real, intent(in)  lon, type(position), intent(in)  lastpos  )

private

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Find a location lat,lon in lolat,lon grids Assumes that the lat/lon grids are semi-regular (dx/dy aren't constant but they are nearly so) Calculates dx/dy at the middle of the lat/lon grids, then calculates the location of lat,lon input point using those coordinates. Next proceeds to calculate a new position based on the dx/dy at that position until the new position is within 1 gridcell of the current position Once that "within 1" position is found, search all cells in a 3x3 grid for the minimum distance return a position datatype that includes the found x/y location

currently tries up to three methods to find the location 1) assume relatively even dxdy and compute location (iterate a <20times) 2) use a log(n) search (divide and conquer) also iterate <20times) a) if 1 or 2 are approximately successful: search a small region around the "best" point to find the real best point 3) in the diabolical case where 1 and 2 fail (rare) just search every single location (n^2) Could add a 2.5) downhill search algorithm...

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type(fourpos) function geo::find_surrounding ( class(interpolable_type), intent(in)  lo, real, intent(in)  lat, real, intent(in)  lon, type(position), intent(in)  pos, integer, intent(in)  nx, integer, intent(in)  ny  )

private

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Given a closest position, return the 4 points surrounding the lat/lon position in lolat/lon

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subroutine, public geo::geo_interp	(	real, dimension(:,:,:), intent(inout)	fieldout,
		real, dimension(:,:,:), intent(in)	fieldin,
		type(geo_look_up_table), intent(in)	geolut,
		logical, intent(in)	boundary_only
	)

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Interpolate fieldout to fieldin using geolut. if boundary_only is true, call boundary_interpolate instead loops over y,z,x but geolut is only defined over x,y (for now)

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subroutine, public geo::geo_interp2d	(	real, dimension(:,:), intent(inout)	fieldout,
		real, dimension(:,:), intent(in)	fieldin,
		type(geo_look_up_table), intent(in)	geolut
	)

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Interpolate fieldout to fieldin using geolut.

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subroutine, public geo::geo_lut	(	class(interpolable_type), intent(in)	hi,
		class(interpolable_type), intent(inout)	lo
	)

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Compute the geographic look up table from LOw resolution grid to HIgh resolution grid

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integer function geo::minxw ( integer, intent(in)  xw, real, dimension(:,:), intent(in)  longrid, integer, intent(in)  xpos, integer, intent(in)  ypos, real, intent(in)  lon  )

private

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Find the minimum next step size in the x direction xw=minxw(xw,lolon,xc,yc,lon)

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integer function geo::minyw ( integer, intent(in)  yw, real, dimension(:,:), intent(in)  latgrid, integer, intent(in)  xpos, integer, intent(in)  ypos, real, intent(in)  lat  )

private

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Find the minimum next step size in the y direction yw = minyw(yw,lolat,xc,yc,lat)

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The documentation for this module was generated from the following file:

• utilities/geo_reader.f90