At the time that I write this the temperature at this desk is 12.7 degrees Centigrade. Of course it will warm up soon, but overnight the temperature drops dramatically at this time of year. I hate the cold. As the saying goes it makes your bones ache.
The climate here is “cool to warm temperate”. This means that places in the south see low temperatures which drop to zero degrees Centigrade or a few degrees below, with occasional falls to lower temperatures in some places. Snow rarely lasts long except of course in the mountains and hills.
In the north, places like Auckland rarely drop to zero, remaining a few degrees above zero in most winters. Auckland and further north rarely experience snow, and a flurry of sleet in Auckland would usually gets a mention on the television news.
While snow rarely lasts long at low altitudes, it tends to come in quantity when it does, closing hill roads and even sometimes brings southern cities to a halt. Dumps at higher altitudes can of course cause severe issues to farmers. The farmers’ worst nightmare is a dry summer and autumn resulting in low yields from pastures followed by an early heavy fall of snow.
Of course the skiers rejoice when there is a snow dump and they head for the many ski fields in their hundreds sometimes causing traffic jams on the access roads! Snow for skiing can be undependable so most major ski fields have snow generating machinery as a backup.
When the snow melts the rivers rise of course. New Zealand rivers can be chillingly cold as a result. Many parts of the country have what is know as braided rivers, which appear to be mostly boulder filled for much of the time. Sometimes during a dry spell it may be possible to cross the river from bank to bank without getting one’s feet wet, while a surprising amount of water travels below the surfaces between the boulders.
When there is a thaw or after heavy rain such rivers rapidly fill and the water rises to the surface, creating a broad and sometimes heavy flow filling the river bed from bank to bank. The flow can be impressive, carrying large trees and other debris from the higher altitudes down to the lower altitudes.
Consequently there are long bridges on these braided rivers that seem to mostly traverse an expanse of rocks and boulders with maybe a relatively small looking river, possibly split into several channels.
Sometimes the boulder banks are populated by Russell lupins, which can block and change the nature of these braided rivers. While picturesque, the lupins are an introduced species and can damage the river’s ecosystem.
The water in the rivers is cold and can be bone-achingly cold as the water is mainly melted snow from the Southern Alps and other mountain ranges. Consequently swimming in such rivers can be challenging. I have swum in a river in the United Kingdom, wearing a wetsuit, with chunk of ice floating down the river, and that was an experience that I will not forget. The rivers here are likely to be at least as cold.
Ice is a strange substance. Well, perhaps that should be water is a strange substance. As water is cooled its volume reduces, like other substances. When it reaches four degrees Centigrade however it reaches a maximum density and then starts to expand again, which is counter intuitive. The reason for this behaviour is related to the way that water molecules link weakly to one another, as a result of the polar nature of the water molecule.
So water at 3 degrees Centigrade is lighter than water at 4 degrees Centigrade and so tends to move to the surface of the water. At 0 degrees Centigrade the water turns to ice, which floats on top of the liquid. This allows all sorts of things and protects fish and other aquatic organisms from the elements and from freezing solid, up to a point. It also allows us to skate on the surface of frozen bodies of water since the slight pressure of the blades causes the ice to temporarily melt.
When a human body gets cold, the body has various defences. As warm blooded animals we need to maintain our body temperature and if we don’t we die. So, when we get cold, blood flows to the centres of our bodies to maintain our core temperature, which means that our hands and feet become significantly colder than the rest of our bodies.
If the cold reaches into our core bodies, things start to shut down and hypothermia sets in. Brain function is hit hard and we start to behave irrationally and we would be in danger of dying. Fortunately as humans we have invented things like fire, houses, and clothing to keep us warm when the weather is cold. I personally have problems with maintaining heat as I do not like to wear gloves and I don’t like any form of headgear!
Another thing that I find in cold weather is that my breath passes over my moustache and beard so in colder weather the moisture in my breath condenses on my moustache and beard making them wet, and if it is cold enough the condensed moisture will freeze. My moustache and beard develop icicles.
On cold days everyone likes to sit beside the fire. An open fire, though, is horrendously inefficient! Even a free-standing stove, which radiates heat into the room, sends much of the heat directly up the chimney or flue. Even the radiant heat quickly rises to warm the air in the ceiling of the room. To add insult to injury, the air that keeps the fire burning is drawn from other places in the house, and has to be replaced by cold, cold air drawn into the house making these other places even colder.
I’ll conclude by noting that the days are becoming longer and while we are still in the depths of winter, spring is around the corner. Indeed, some early blooming plants are already showing signs of life, although they won’t amount to much until later in the year. The day length here will increase by one minute and 11 seconds tomorrow, and this rate of increase will grow rapidly until the equinox (around 21 September) by which time we should be much more cosy. However due to seasonal lag, we may still have the coldest times for this year ahead of us.