Let it Snow, Let it Snow, Let it Snow
It isn't exactly seasonal but this
month's MOO Report is on snow. Due to its
geographical position, Bournemouth rarely receives snow,
and only a sprinkling when it does - unfortunately never
enough to miss school! Nevertheless, in a wider context
snow is both important and interesting to meteorologists.
The story of snow begins when super cooled
water forms in the atmosphere. A requirement is that the atmospheric temperature
is less than 0 degrees Celsius, the freezing point of water. The second
condition is that there must be a nucleus for crystals to form around -
typically these nuclei are dust particles. The size of the snow particles which
form depends on a number of factors, but particularly important are water
content and atmospheric temperature.
When snow falls it can be categorised by
meteorologists or scientists by the amount of time it covers the ground. Most
common in the UK is temporary snow cover, which lasts for just a few days at
most. There are two other categories; seasonal - when areas are covered for
months at a time, typically mountains in water at low latitudes like the UK or
summer months in high latitudes; and additionally permanent.
Snow is both loved and hated. Whilst it can be
great fun to play around in (or force days off school!) it can also be
treacherous. Meteorologists are invaluable in producing information regarding
snowfall on motorways, for instance. Additionally, they can often predict when
avalanches will happen.
Avalanches are more likely to happen in a
snowpack if the temperature on the ground rises quickly, if there is rainfall or
if there is fresh snowfall. In many skiing resorts, meteorologists are employed
to forecast these conditions in order to make a prediction of likeliness of
avalanches. If meteorologists think there will be a dangerous avalanche, they
can advise managers on evacuating the area.
MOO realises that avalanches
are fascinating to many of its readers; watch out for other MOO
reports about prevention of avalanches in the near future!