# fluxEddy

Calculates time averaged eddy flux quantities.

Note: This function is only available in version 4.1.1 of NCL. If your site is licensed for version 4.1, then you can get version 4.1.1 for free. To get version 4.1.1 of NCAR Graphics software, please contact your site representative. If you don't know who your site representative is, then send email to ncarginf@ucar.edu or call (303) 497-1201.

## Synopsis

```    function fluxEddy(
x  : float,
y  : float
)

```

## Arguments

x
A float array with one or more dimensions. The rightmost dimension must be "time". Missing values should be indicated by x@_FillValue. If x@_FillValue is not set, then the NCL default (-999) will be assumed.
y
A float array with one or more dimensions. It must have the same dimensions as x. Missing values should be indicated by y@_FillValue. If y@_FillValue is not set, then the NCL default (-999) will be assumed.

## Description

fluxEddy returns a float array of the same dimensionality as its input arrays with the last dimension omitted. The resulting quantities are computed in one pass. The approach used is let x=X+x' and y=Y+y' where X and Y are time averages, then x'y' = ave{x*y} - X*Y. Missing values are allowed.

## Example 1

Let x and y be dimensioned nlat x mlon x ktimes (nlat=64, mlon=128, ktimes=90):
```    xpyp = fluxEddy (x,y)   ; xpyp=x'y' will be an nlat x mlon array
```

## Example 2

Let u and v be dimensioned ntimes x klev x nlat x mlon with named dimensions "time" , "lev" , "lat" , "lon". Then:

```    upvp = fluxEddy (u(lev|:,lat|:,lon|:,time|:), v(lev|:,lat|:,lon|:,time|:))
```
upvp will be a 3-dimensional array dimensioned klev x nlat x mlon.

## Example 3

To calculate the eddy variance of a quantity z. (I.e. ave{z'z'}):

```    zpzp = fluxEddy (z,z)
```
or

```    zpzp = fluxEddy (z(lev|:,lat|:,lon|:,time|:), z(lev|:,lat|:,lon|:,time|:))
```
depending upon the dimension order.

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\$Revision: 1.3 \$ \$Date: 1999/03/22 20:49:09 \$