Date: Sun Aug 11 2013 - 02:57:55 MDT
hi,
i met a question when using interpolation function for filling in missing value in land surface,
so made two function for comparsion:
1. first , poisson_grid_fill
the following figure is from poisson interpolation for air temperature, but it's strange for so many few low value occurrence.
this is my part code for interpolation:
.............................
.............................
;-----------------------------------------------------------------
; Set the poisson_grid_fill variables
; Global grid: Fill in over land
;-----------------------------------------------------------------
nscan = 2000 ; usually *much* fewer
eps = 0.001 ; variable depended
gtype = True ; Cyclic in longitude [global]
guess = 0 ; use zonal means
relc = 0.6 ; standard relaxation coef
opt = 0
lsm=addfile("$NCARG_ROOT/lib/ncarg/data/cdf/landsea.nc","r")
lsm_t2m=landsea_mask(lsm->LSMASK,t2m&lat,t2m&lon)
t2m=mask(t2m,lsm_t2m.eq.0,False)
;; poisson interpolation
poisson_grid_fill( t2m, gtype, guess, nscan, eps, relc, opt)
t2m=mask(t2m,lsm_t2m.eq.0,False)
.....................................
if i make a linear interpolation with linmsg function, then will obtain good effect.
2. linmsg function, the effect is as below:
the part of ncl codes is:
..........................
..........................
Origt2m = t2m ;; save origin grid for later plot
lsm=addfile("$NCARG_ROOT/lib/ncarg/data/cdf/landsea.nc","r")
lsm_t2m=landsea_mask(lsm->LSMASK,t2m&lat,t2m&lon)
t2m=mask(t2m,lsm_t2m.eq.0,False)
;; linear interpolation
t2m=linmsg(t2m,-1)
t2m=mask(t2m,lsm_t2m.eq.0,False)
................................
................................
i wonder why so obvious difference appeared between this two methods?
dyjbean
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