[ferret_users] after scat2gridlaplace some values are obsolote (data origins of lambert grid)

[Peter Szabo <szabpet83@xxxxxxxxx>]

Dear Users,

I have a daily precipitation data set on a lambert grid stored in ASCII file. 
I wanted to put this on a lat-lon grid with functions scat2gridlaplace and/or scat2gridlaplace. (After ferret cant deal with Lambertian data sets  and I want to make some computations thats why i change its grid)
Somehow after the scat2gridlaplace my data contains truly negative values. Does anyone know what mistake could i make? Or is it the function thats not working properly?

Here is my script:

DEFINE AXIS/x=12.42:24.6/np=97 lons
DEFINE AXIS/y=44.9:49.92/np=61 lats
DEFINE AXIS/t="1-JAN-1961 12:00":"31-DEC-1990 12:00":1/t0="31-DEC-1960 12:00"/units=days time

DEFINE GRID/t=time/x=lons/y=lats gridxyt
DEFINE GRID/x=lons/y=lats gridxy

SET DATA/EZ/VARIABLES="lon,lat"/GRID=gridxy "ASCII_koord.txt" !->i need the coordinate values from this file
let xx1D = XSEQUENCE(lon[d=1])
let yy1D = XSEQUENCE(lat[d=1])

SET DATA/EZ/VARIABLES="pre"/GRID=gridxyt "predaily.txt"

fill pre[l=@sum],lon[d=1],lat[d=1]  !->I attach the picture of the original data (AA.lambert.gif) created with similarly to this command

let precipG=scat2gridgauss_xy(xx1d,yy1d,pre,x[gx=lons],y[gy=lats],0.01,0.01,10,0)
fill precipG[l=@sum] !-> the data looks like this after the gaussian weightening (AA.gauss.gif)

let precipL=scat2gridlaplace_xy(xx1D,yy1D,pre,x[gx=lons],y[gy=lats],100,100)
fill precipG[l=@sum] !-> the data looks like this after the laplace interpolation (AA.laplace.gif)

Now the data is on a lat-lon grid and both looks pretty the same, but if i count the minimum of the daily data the actual values are negative in the case of scat2gridlaplace. (i attach also the minimum value of the "laplace" data set. the two others dont have negative values larger than 0.05).
I know i should use the gaussian weightening and interpolation, but this bug/my fault still troubles me.

Thanks in  advance,
Peter Szabo

Attachment: AA.lambert.gif
Description: GIF image

Attachment: AA.gauss.gif
Description: GIF image

Attachment: AA.laplace.gif
Description: GIF image

Attachment: AA.laplacemin.gif
Description: GIF image