Re: Question on the correlation pattern plot ?

>I have a question when I want to get a correlation field
>between PDO and NH precipitation.

>1. I met an error when dealing with rtest of cross correlation ,
> error info : "SLATEC/NCL: DBETAI: P AND/OR Q IS LE ZERO:
> NERR= 2: LEVEL= 2" and codes were listed below :
>
> ccr1 = escorc(pdo({1951:2002}),ann_cru(:,:,{1951:2002}))
> nlat = dimsizes(ccr1(:,1)) ; nlat= 180 for North Hemisphere
> nlon = dimsizes(ccr1(1,:)) ; nlon = 720
                                  ^^^^^^^^^^^^^
                                  CRU ... this does not look correct
> print(nlon)
> print(nlat)
> Nx1 = new((/nlat,nlon/),"integer")
> do ilat = 0,nlat-1
> do ilon = 0,nlon-1
> Nx1(ilat,ilon) = num(.not.ismissing(ann_cru(ilat,ilon,{1951:2002})))
> end do
> end do
> prob1 = rtest(ccr1,Nx1,0)

>I believe that it is because Nx1 have many constant
>missing value in ocean area that cause such trouble.
>But I can not find a way to resolve it.
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Oops! The underlying code computes the degrees of freedom via
           
           df = n-2
           
       When "n" is 0 [as returned by dim_num], then df is -2.
       The documentation and wrapper will be changed for the
       next release of NCL [a035].
       
       The following is a workaround. Since I think meta
       data is useful, I have added some extra stuff.
       

  ccr1 = escorc(pdo({1951:2002}),ann_cru(:,:,{1951:2002}))
  copy_VarCoords(ann_cru(:,:,0), ccr1) ; copy lat/lon coord information
  ccr1_at_long_name = "r: PDO-CRU"
  printVarSummary(ccr1)
  printMinMax(ccr1, True) ; contributed.ncl
  
  
  Nx = dim_num(.not.ismissing(ann_cru(:,:,{1951:2002})))
  copy_VarCoords(ccr1, Nx) ; contributed.ncl
  Nx_at_long_name = "number of non-missing values"
  printVarSummary(Nx)
  printMinMax(Nx, True)
  
  dim_ccr1 = dimsizes(ccr1)
  nlat = dim_ccr1(0)
  mlon = dim_ccr1(1)
  
  prob = new ( dim_ccr1, "float", -999.)
  
  do nl=0,nlat-1
    do ml=0,mlon-1
       if (Nx(nl,ml).gt.2) then
           prob(nl,ml) = rtest(ccr1(nl,ml),Nx(nl,ml),0)
       end if
    end do
  end do
  
  prob_at_long_name = "probability"
  copy_VarCoords( ccr1, prob)
  
  printVarSummary(ccr1)
  printMinMax(ccr1, True)

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Received on Mon Jan 22 2007 - 11:12:33 MST