Shed­ding some light on the water

The News (New Glasgow) - - WEATHER -

The drive from the fam­ily farm back to the air­port is al­ways bit­ter­sweet; it’s also quite beau­ti­ful.

Last Sun­day, as we crossed one of the bridges that takes us onto the Is­land of Mon­treal, Mom com­mented on how lovely the water looked; I added that it looked cold. That got us talk­ing about the colour of the water. I’m sure you’ve no­ticed that the same body of water can look very dif­fer­ent from one sea­son to an­other but also from one day to an­other. The colour you see de­pends on two things: the con­cen­tra­tion and na­ture of the or­ganic and in­or­ganic par­ti­cles in the water and the re­flec­tion of light at the sur­face of the water. Let’s start with ba­sics of colour: Colour is what you see when light isn’t ab­sorbed by an ob­ject. In other words, it’s the re­sult of the wave­length of light that is re­flected from an ob­ject; in this case, the water. The at­mos­phere, for ex­am­ple, ab­sorbs all the colours ex­cept blue which is scat­tered by the ni­tro­gen atoms that are pre­dom­i­nant in our air. The light, and there­fore the colour re­flected that our eyes see, is more a func­tion of light ab­sorbance and scat­ter­ing by the ob­jects re­flect­ing light.

Now if the water has a high con­cen­tra­tion of par­tic­u­late mat­ter, the water colour can take on a green or murky look. Pure water is very blue. The sec­ond fac­tor in de­ter­min­ing the colour of water in a lake of river is, be­lieve it or not, cloud cover. Water re­flects what is hap­pen­ing in the sky. Fall clouds – the low, heavy dark clouds – block out the light and cast the water in shades of sil­ver, greys, and mauves.

Sun­ning Stun­ning Asper­i­tas clouds - for­merly known as Un­du­la­tus as­per­a­tus. This cloud for­ma­tion was first pro­posed as a type of cloud in 2009 by Gavin Pre­tor-Pin­ney of the Cloud Ap­pre­ci­a­tion So­ci­ety. (Con­trib­uted)

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