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

[Peter Szabo <szabpet83@xxxxxxxxx>]

Dear Ansley and Edward,

I tried using SCAT2GRIDLAPLACE_XY with 5-5 for the last two arguments (instead of 100-100), but the results were almost the same (negative values still appeared among precipitation values). 
I also tried using 0 for CAY (=Laplacian interpolation is used) and 5 (the default) for NRNG arguments, but the results got worse (see attached AA.0caymin.gif). 

As for the CURVE_TO_RECT function: the results made with the below commands were not satisfying. I dont have a clue what is wrong with this.

SET DATA/EZ/VARIABLES="lon,lat" "ASCII_koord.txt"
let lons=lon[d=1]
let lats=lat[d=1]
def axis/t="1-JAN-1961 12:00":"31-DEC-1990 12:00":1/t0="31-DEC-1960 12:00"/units=days time
def grid/t=time/x=xlon/y=ylat gridxyt

SET DATA/EZ/VARIABLES="precip"/grid=gridxyt "predaily.txt"

def axis/x=12.42:24.6/np=97/modulo xax
def axis/y=44.9:49.92/np=61 yax
let lonlatout = y[gy=yax] + x[gx=xax]
let map = curv_to_rect_map ( lons,lats,lonlatout,0.5)
let pre = curv_to_rect(precip[d=2], map)

So i might use the GAUSSian grid-changing function to have my lambert (curvilinear) data on lat-lon, rectilinear grid.

Peter

On Tue, Feb 24, 2009 at 11:54 PM, E. D. (Ned) Cokelet <Edward.D.Cokelet@xxxxxxxx> wrote:

FYI, mathematically if a function satisfies Laplace's equation: del-squared F = 0, then its maxima and minima must lie on the boundary of its domain and nowhere else.  It is like a rubber sheet stretched over a drumhead with highs and lows on the rim of the drumhead.  The rubber sheet will conform to the boundary and values out in the domain will be an average of (and always less extreme than) those on the edge.  So if the Ferret Laplacian gridding is working correctly, this property must hold (within numerical rounding error and loss of significant figures).  

------------------------------------------------------------------------------------------

Edward D. (Ned) Cokelet, Ph.D. Oceanographer

NOAA/PMEL                         off:  (206) 526-6820

7600 Sand Point Way NE     fax: (206) 526-6485

Seattle, WA 98115-6349

Edward.D.Cokelet@xxxxxxxx

The contents of this message are mine personally and do not necessarily reflect any position of the Government or the National Oceanic and Atmospheric Administration.

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