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50 Earth

HOW DO EXPERTS PREDICT THE WEATHER?

Meteorologists receive information about air

temperature, wind speeds, clouds, and rainfall

from over 50,000 weather stations worldwide –

on land and on ships and buoys at sea. The

data is fed into huge computers, which

produce charts and forecasts. These are used,

with satellite images, to predict the weather.

A weather forecast is a prediction of

weather conditions over a particular area,

either for a few days (called a short-range

forecast), or for several weeks (called a

long-range forecast). The people who study

the weather and make weather forecasts are

called meteorologists.

WHY DO WE NEED WEATHER FORECASTS?

Weather forecasts help people to plan – from what to

wear, when to travel, and which products to stock in

supermarkets. Forecasts are especially important for

farmers, builders, sailors, and anyone else who works

outdoors. Sometimes, an accurate forecast may mean

the difference between life and death.

Weather is what is happening in the

atmosphere now, at any place on

the Earth’s surface. It includes the

temperature and whether it is wet

and windy or dry and calm.

4 MAPPING THE WEATHER

Weather experts monitor the

movements of air masses and

clouds using satellite images.

The images are coloured by

computer to pick out the

movement of clouds. This false-

colour satellite image shows

winds spiralling over the

Atlantic Ocean, indicating

unsettled, stormy weather.

1 MORNING MIST

Fog over the Golden Gate Bridge in San Francisco, USA, usually burns

away quickly in the heat of the morning Sun. Weather conditions can

change daily, hourly, or even from minute to minute.

Weather

STORM TRACKING 3

A meteorologist tracks a storm

using images taken by satellite.

Weather centres issue weather

warnings to all regions in

the storm’s path.

FORECASTS

Winds swirl around an area

of low pressure, created when

a mass of warm air is forced

upwards by a mass of cold air

Image of spiralling winds

photographed by a weather

satellite is displayed on a

computer screen

Low-level clouds are shown

in yellow; high-level clouds

appear white

Supercomputers condense

the huge amount of data

from satellites

HOW DO WEATHER SATELLITES WORK?

Weather satellites carry two types of

sensor. An imager takes photographs

of movements in the Earth’s

atmosphere. A sounder reads the

temperature of the air and clouds.

WHAT CAUSES THE WEATHER?

The Sun provides the energy that drives the Earth’s

weather. The Sun heats the air in various parts of the

Earth’s atmosphere by different amounts. Masses of

warm and cold air then move from place to place,

creating winds. Winds bring sunny, wet, or stormy

conditions. People find out the type of weather to

expect in a. FORECAST.

FIND OUT MORE. Atmosphere 49 • Climate 62 • Rain 52–53 • Winds 51

weather