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Re: symmetric anomalies?



Haldor,

You can reverse the Y axis on a variable with the SAMPLEJ external
function available in Ferret 5.x.  Use the same technique with SAMPLEI
to reverse the X axis.

yes? use coads_climatology
yes? show data
     currently SET data sets:
    1> /opt/local/ferret/fer_dsets/descr/coads_climatology.des 
(default)
 name     title                             I         J        
K         L
 SST      SEA SURFACE TEMPERATURE          1:180     1:90      ...      
1:12
 AIRT     AIR TEMPERATURE                  1:180     1:90      ...      
1:12
 SPEH     SPECIFIC HUMIDITY                1:180     1:90      ...      
1:12
 WSPD     WIND SPEED                       1:180     1:90      ...      
1:12
 UWND     ZONAL WIND                       1:180     1:90      ...      
1:12
 VWND     MERIDIONAL WIND                  1:180     1:90      ...      
1:12
 SLP      SEA LEVEL PRESSURE               1:180     1:90      ...      
1:12

yes? ! Here we define an index which samples from hi to lo along J
yes? let reverse_j = 90 - j[g=sst]
yes? let sst_reverse_j = samplej(sst,reverse_j)
yes? shade/j=45:90/l=1/lev=20c sst-sst_reverse_j
 *** NOTE: Ambiguous coordinates on Y axis: SST-SST_REVERSE_J


-- Jonathan Callahan



Halldor Bjornsson wrote:
> 
>  Hi,
> 
> Does anyone know how to tell ferret to generate "symmetry anomaly fields"?
> 
> 
>  An example would be the following:
> 
>     Given SST field extending
>     from 60S to 60N, plot SSTANO, which is defined as difference
>     between the north and the south hemispheres (the line of symmetry
>     being the equator):
> 
>        SSTANO = SST(from 60S to 60N) - SST(from 60N to 60S)
> 
>        Its important to note that Lat S should map to the same Lat N,
>        (i.e give difference between 50S and 50N, etc.)
> 
>  Likewise one could generate an anomaly plot where the line
>  of symmetry is a given longitude and w'ed get an east-west
>  anomaly field.
> 
>  If anyone has ideas on how to do this please share them with me, -
>  I'm kindoffa stuck here...
> 
>  Thanks
> 
>  Halldor
>  --
>  -----------------------------------------------
>  Halldor Bjornsson
>  Program in Atmosphere and Ocean Science &
>  Geophysical Fluid Dynamics Laboratory
>  Princeton University, Princeton, NJ USA
>  email: hnb@gfdl.gov
>  -----------------------------------------------
>


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