Every day we
experience the weather and the effects that come with it, whether it’s the grey
clouds and drizzle we so often see, or the rare occurrence of hot sun with
clear blue skies. But as you become drenched in the April showers, or get
thrown about in gale force winds; just take a moment to think; what is actually
causing these natural phenomena’s to take place?
What Causes Our Rainfall?
Rainfall is
one of the most common weather types in England, and one that I’m sure has
ruined many hours of carefully perfected hair-dos, but why do we seem to get
rain so much more than any other country? Well, it’s all to do with things
called jet streams which criss-cross
the earth at around 20,000ft above its surface and are basically narrow bands
of very strong westerly winds. The UK is at just the right latitude that the
polar jet stream passes right over it, and because of this, areas of low and
high air pressure are formed, which in turn create similar patterns in sea
pressure.
These
changes in sea pressure affect the movement of winds and cause a common weather
feature called depressions to form.
Depressions are regions of low pressure which produces rainy and windy weather,
and is the main cause of the miserable and changeable weather we so often see
in the UK. Quite simply, a depression forms when a large mass of cold air meets
a large mass of warm air, with the cold air usually coming from Polar Regions
and the warm air from the Tropics. Heavy rain and strong winds form where these
two air masses meet because the warm air rises over the cold air and condenses
to form rain clouds.
How about our Snowfall?
We have
explained the cause of the wet and wind that we are so used to in the UK, but
how about snowfall? It may not be such a common occurrence, but still... why do
we get it?
As we have already found out, the majority of the UK’s weather is
determined by the polar jet stream, which brings us wet and damp weather in the
form of depressions. However during winter, the oceans are normally
much warmer than the land because they take longer for them to change
temperature, and because of this, an area of high pressure forms above them and
this interferes with our usual jet stream position.
When this newly created area of high pressure forms over the Atlantic, our
usual jet-stream becomes blocked, and instead of flowing right over the UK as
normal, it is actually deflected southwards slightly – allowing chilled air
from the north to flood into its place – and where our usual Atlantic weather
system meets the cold front from the north, snow falls. The UK was stuck like this for several weeks in
2010, which was the cause of widespread snowfall.
How About our Warm Weather?
So now all the cold, wet and windy weather is other with, how about the
hot weather? This may seem like an even rarer occurrence in this country, but
nevertheless it does happen.
The cause of these blissfully hot days and clear blue skies are from a
weather phenomenon called anti-cyclones. These anti-cyclones are the opposite
of depressions and are instead areas of high pressure where the air is
constantly sinking, as opposed to rising in a depression, but why does this
cause nice weather, and not bad?
Well, because this air is sinking instead of rising in an anti-cyclone, clouds
aren’t formed which means that no rain can be produced, and the fact that there
are no weather fronts also means that no wind can form. If an anti-cyclone was
to form during the summer then would most likely bring warm weather with clear
skies; while if in winter, then it would bring clear but cold days, with frosty
nights. The weather will always be consistent and unchanging as long as an
anti-cyclone is present.
So, there’s a quick introduction into the causes behind our country’s weather
for you, and hopefully the next time you look out of your window, deciding what
clothes to wear for the day and see the all-too familiar grey clouds forming
above, you’ll know a little more about why it’s all happening.
