Weather, Climate and Chaos
Physics can tell us a lot about what the weather is going to be like, but it can
never tell us the whole picture. Why is this? Surely the weather follows rules and
mathematical formulae. Why do forecasters not always get it right, sometimes
with serious consequences?
Firstly, let’s tie down some definitions
How would you define the word ‘weather’?
How is this different from the ‘climate’?
Try to describe the climate of Britain.
Can you do the same for the weather?
Go to www.dictionary.com to check some of your definitions.
How good are our forecasts?
The BBC publish five day forecasts for lots of locations. Do they get it right 5
days in advance?
Find the five day forecast for your location at www.bbc.co.uk/weather. Is the
forecast for today right?
Here is an example of a 5 day forecast for Oxford:
On Monday, the 5 day forecast was
On Tuesday it looked like:
On Wednesday it looked like:
So why can the weather be so unpredictable
Forecasting the weather depends on a lot of variables.
List as many of the variables as you can below.
Now go to http://www.meteo-technology.com/metvar.htm to see a full list of
meteorological variables.
Not all of these are used commonly in forecasting.
To see the common ones, and to get an idea of the complexity of weather
forecasting, visit www.bbc.co.uk/weather/weatherwise and find out how weather
forecasting works.
You should have found that 1,187,500 items of atmospheric data are collected at
any one time for use in forecasting.
This is the main problem. To make an entirely accurate prediction of the weather
we’d need to know that exact situation at any one time. With so many things to
consider, and so much of the atmosphere to cover, this is just not possible. We
have to make generalisations and this can lead to problems…
Chaos
Not knowing the initial situation for something as complex as the weather makes
it difficult to predict. There are other, simpler situations where a small change in
the starting conditions can lead to a big change in the result.
Open the Excel file ‘the logistic equation.xls’ and follow the instructions there.
Make some notes about the behaviour you have observed.