By Helena & Laura

Contents

•Introduction

•Precipitation

•Clouds

•Sunshine

•Wind

•Storms

•Visibility

•Temperature and Climate

•Extremes

•Rainbows

Introduction

Weather is the state of the atmosphere in any given place for a short period of time and climate is the average weather for a larger area (e.g. Country, Continent).

Precipitation

Precipitation is a broad term meaning water that falls from the sky. However, precipitation has lots of forms. Usually given in millilitres (ml) it is measured using a rain gauge.

Water that falls to the ground as droplets is known as rain or sometimes drizzle. Most raindrops are 2-5mm in diameter, and fall at 14-20 miles per hour.

Hail is frozen rain. It only falls from cumulonimbus clouds. Hail stones are usually 5-50mm across.

Snow is made up of snowflakes, which are formed when ice crystals bang into each another. Each flake is different, but they are all six-sided.

Frost is a layer of ice crystals which covers cold surfaces.

Dew (condensed water vapour) forms late at night if the air is moist, after objects lose the heat they have absorbed during the day. If it freezes, it changes into ice.

Most forms of precipitation can be found on the Water Cycle.

Clouds

Clouds are made of ice crystals or rain.

Cloud cover means how much of the sky is hidden by cloud. Usually given in oktas, it is measured using your eyes or a satellite image.

Types of cloud:

Stratus

Stratocumulus

Cumulus

Cumulonimbus

Cirrus

Stratus

Description: A grey layer with no gaps or features that covers most or all of the sky.

Occurrence: Most common in winter.

Distribution: Worldwide, but more common near mountains or coasts.

Level: Low, usually lower than 2000m.

Stratocumulus

Description: Patches or sheets of white or grey cloud with a textured look.

Occurrence: All year.

Distribution: Worldwide.

Level: Low, with a base below 2000m.

Cumulus

Description: Separate from each other, cumulus clouds appear bright, fluffy, white and with blue sky between.

Occurrence: Most common in summer.

Distribution: Worldwide, common in humid regions.

Level: Low, usually below 2000m.

Cumulonimbus

Description: Made up of liquid droplets near the bottom and ice crystals nearer the top, cumulonimbus clouds are vertical, and produce rain, hail, snow and tornadoes. It is the only cloud that produces hail.

Occurrence: All year.

Distribution: Worldwide, except Antarctica.

Level: Low to high

Cirrus

Description: Made up completely of ice crystals, cirrus clouds are wispy, thin and look fibrous.

Occurrence: All year.

Distribution: Worldwide.

Level: High.

Sunshine

The sun gives off light during the day. Sometimes it appears to be

covered by clouds, but it is always giving us light otherwise we would be in darkness. The earth rotates every 24 hours so at one time half the earth is facing away from the sun. This gives us day and night. The earth orbits the sun once a year. This gives us seasons.

Wind

Wind is the movement of air from high pressure areas to low pressure areas. Wind direction is where the wind is coming from ( South West wind blows from the South West). It is given as a compass bearing (e.g. N, NW, SE). Wind direction is measured with a wind vane. Wind speed is how fast the wind is blowing. It’s usually given in miles/kilometres per hour, and it’s measured using an anemometer.

Storms

A typical thunderstorm is made up of Cumulonimbus clouds and some form of precipitation. Hailstones and ice crystals collide making particles with positive charge go to the top of the cloud and particles with negative charge go near the bottom. This encourages lightning when the charge reaches a high level.

Sheet lightning is between two clouds or two areas of a cloud and forked lightning flashes between a cloud and the ground.

The lightning heats the nearby air to over 30,000°C in less than a second so it explodes. The noise of the explosion is thunder.

Visibility

Visibility is how far ahead of us we can see. For example, on a foggy day, we would not be able to see as far ahead of us as we would on a clear day. Usually given in metres (m) or kilometres (km,) it’s measured using the eyes or a visibility meter.

Fog is exactly the same as cloud except that it touches the ground. It makes visibility difficult.

Temperature & Climate

Temperature is how hot or cold it is- and obviously this differs for different parts of the world (the Arctic: -40 degrees, Greece: 40 degrees.) Temperature is given in degrees Centigrade (˚C) but sometimes in degrees Fahrenheit (˚F) and it is measured using a thermometer.

Temperature is also a huge part of climate. Climate is the average weather for a larger area of land. Climate can be very extreme. The Sahara desert, (hot and dry) and the Arctic (freezing cold and covered in ice) are pretty much on opposite ends of the scale.

Click to view a Climate Map of the World

ExtremesHurricanes start out at sea with storm clouds , torrential rain and howling winds of up to 300km/h. All this makes huge waves on the sea below. When a hurricane moves over land, incredibly strong winds destroy houses and property and a storm surge (a huge wall of water whipped up by the wind) can completely flood a town in sea water.

A hurricane is formed when the sea heats the air and warm moist air rises. Winds drive the moist air up high so it cools and forms huge clouds. The clouds turn round the centre of the hurricane (the eye) which is calm but the storm is worst just outside the eye.

Tornadoes can reach speeds of 600km/h. They occur when a mass of cool dry air meets a mass of warm moist air. Cumulonimbus clouds form and sometimes the air in the clouds starts to rotate and forms a tornado. If a tornado hits a city it can cause total destruction.

Rainbows

Rainbows are an effect of sunlight shining through rain drops.

The raindrops are like crystals and split the white sunlight into lots of different colours.

This means that the position of a rainbow depends on where the sun is, where the rain is and where you are. That means that if any of these things move the rainbow moves.

Thank you for watching Sources:• Google• Wikipedia• ‘Earth’ by Dorling Kindersley (Editor:

James F. Luhr)• BBC- Bitesize- Clouds

Helena Wilson and Laura Dallaway8a1