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This function computes the average of each a field in a fieldset over an area. The computations are based on the assumption that all the cells have the same extent in latitude and the individual cell areas can be approximated with
Mathdisplay |
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A_{i} = 2 R^{2} cos\phi_{i} sin(\frac{\Delta\lambdaphi_{i}}{2}) cos(\Delta\phi)lambda_{i} |
where:
R
is the radius of the Earthφ
i is the latitude of the i-th grid cell
is the size of the grid cells in latitude (constant)Δ
φΔλ
i is the size of the i-th grid cell in longitude.
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