What does SWH mean in Unclassified?

Significant wave height

In physical oceanography, the significant wave height is defined traditionally as the mean wave height of the highest third of the waves. Nowadays it is usually defined as four times the standard deviation of the surface elevation – or equivalently as four times the square root of the zeroth-order moment of the wave spectrum. The symbol Hm0 is usually used for that latter definition. The significant wave height may thus refer to Hm0 or H1/3; the difference in magnitude between the two definitions is only a few percent.

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