Weather measurements from a distance
You don't have to put an instrument in a rain shower or a wind
storm to know about the rain or wind. Doppler weather radar
installations can tell, from a distance, precipitation - rain, snow
and hail - location and intensity as well as wind strength and
A Doppler radar station at
Buckland Park (cc) Fairv8
Doppler radar sends out microwave pulses to a weather target.
The weather target reflects the pulse back to the radar, where it
can be measured. The reflection tells us about what sort of
rain or snow is occurring at the target. Successive pulses show how
the weather is changing, and help to determine wind speed and
direction to forecast the future position and intensity of the
rain. The distance to the weather target is calculated from the
time the pulse leaves to the time it returns.
A weather balloon carries
instruments high into the atmosphere to record atmospheric
pressure, ambient temperature, humidity and wind speed by means of
a small, measuring device called a radiosonde. They send their data
back to earth using a transponder.
Scientists with weather
Weather balloons may reach altitudes of 40 kilometres or
more, but 25 kilometres is more usual. Every day, at over 750
locations around the world, weather balloons are launched twice
daily. That's a lot of balloons a year - you do the maths! A basic
weather balloon and its transponder cost about £75 to £100.
Does this seem a reasonable data collection expense?
See if you can find out where weather balloons are launched near
you. Many University Departments, and the Meteorological Office,
can arrange school visits to allow you to be present and observe
the balloons going up.
So, that's how raw data is gathered for weather forecasts.
But what happens then? It's not enough just to
gather the weather data - you need to use that data to predict what
will happen to the weather next. Anyone can look out of the window
and see if it's raining - people want to know whether it will rain
the next day, and the day after next. Go to Using a Computer
to Predict the Weather to find out how forecasts are made.