If you’ve surfed long enough – especially in the
southern states – you’ve learnt the hard way that rain
can reduce swell size fairly significantly.WORDS BY KERRY WRIGHTRAINS
Thinking you’re going to be waking
up to macking surf based on
the forecast – only to find it half
the predicted size, thanks to the
pouring rain that accompanied it
in the cold front.
The ancient mariners knew all this
before us, and sailing lore speaks of
how the rain tends to calm the sea.
Here’s how it happens in science-
speak: Rain alters surface roughness
through the production of wavelets
by raindrops, as well as dampening
of high-frequency waves. It reducesenergy in the ocean surface through
non-linear interactions with the
underlying wave field.
Simply put – when raindrops hit the
sea they change the properties of the
surface. Rain causes a uniform increase
in pressure throughout the water
column ’cos of the turbulent dissipation
created by the raindrops penetrating
the sea surface and by changing
momentum at the surface layer.
If you’ve sat out in the surf in a rain
storm you know how quickly the waves
disappear!WHEN IT
IT