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mjo_cross

Calculate space-time cross spectrum over multiple segments.

Available in version 5.1.0 and later.

Prototype

load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"        ; These three libraries are automatically
load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_csm.ncl"         ; loaded from NCL V6.2.0 onward.
load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl"     ; No need for user to explicitly load.

load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/diagnostics_cam.ncl" ; Still need to load this library.

	function mjo_cross (
		x    [*][*][*] : numeric,  
		y    [*][*][*] : numeric,  
		segLength  [1] : integer,  
		segOverLap [1] : integer,  
		opt        [1] : logical   
	)

	return_val  :  float or double

Arguments

A three-dimensional variable array. Nominally: (time,lat,lon). The longitudes should be global; the latitudes should span just the south-north region of interest; and, the 'time' should span the entire period of interest.

A three-dimensional variable array similar to x. Nominally: (time,lat,lon).

segLength

Length of the segment.

segOverLap

Overlap of the segment.

opt

Currently, not used. Set to False.

Return value

The return variable will be a three-dimensional array (16,wavenumber,frequency) containing the 16 cross spectral quantities averaged over all segments.

         ( 0,:,:)  -  symmetric power spectrum of x
         ( 1,:,:)  -  asymmetric power spectrum of x
         ( 2,:,:)  -  symmetric power spectrum of y
         ( 3,:,:)  -  asymmetric power spectrum of y
         ( 4,:,:)  -  symmetric cospectrum
         ( 5,:,:)  -  asymmetric cospectrum
         ( 6,:,:)  -  symmetric quadrature spectrum
         ( 7,:,:)  -  asymmetric quadrature spectrum
         ( 8,:,:)  -  symmetric coherence-squared spectrum
         ( 9,:,:)  -  asymmetric coherence-squared spectrum
         (10,:,:)  -  symmetric phase spectrum
         (11,:,:)  -  asymmetric phase spectrum
         (12,:,:)  -  symmetric component-1 phase spectrum
         (13,:,:)  -  asymmetric component-1 phase spectrum
         (14,:,:)  -  symmetric component-2 phase spectrum
         (15,:,:)  -  asymmetric component-2 phase spectrum

The returned variable will have the following attributes:

   segmentLength - segment length 
  segmentOverLap - segment overlap 
   segmentRepeat - repeat overlap 
             dof - degrees of freedom 
            prob - (/0.80, 0.85, 0.90, 0.925, 0.95, 0.99/)
       prob_coh2 - coherence-squared levels corresponding to prob

and the following coordinate variables:

   freq - frequencies [ 0.0 to 0.5 cycles per day ] 
   wave - wave number [-M/2 to M/2 where M is the number of longitudes ]

Description

See the Level 2 diagnostics description: US-CLIVAR MJO diagnostics website. Click on "Description"; then the Level 2 "See more specific discussion"

Examples