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# mjo_cross_segment

Calculate space-time cross spectrum for a single time segment.

## Prototype

```	function mjo_cross_segment (
x [*][*][*] : numeric,
y [*][*][*] : numeric,
opt      : integer
)

return_val  :
```

## Arguments

x
y

Three dimensional variable arrays which nominally are dimensioned: (time,lat,lon).
The longitudes should be global while the latitudes should only span the south-north region of interest. The size of the 'time' dimension should be the size of the desired segment length. EG: for daily mean data, the size of the time dimension is typically 96, 128, 256, etc.

opt

Currently, not used. Set to 0.

## Return value

The return variable will be a three-dimensional array (16,wavenumber,frequency) containing the 16 cross spectral quantities associated with the specific time segment.

```         ( 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 coordinate frequencies span 0.0 to 0.5. The coordinate wavenumbers span -M/2 to M/2 where M is the number of longitudes.

## Description

See the Level 2 diagnostics description titled MULTI-SCALE INTERACTIONS at the US-CLIVAR MJO diagnostics website

## Examples

See Example 11 of the Madden-Julian Oscillation web page.