Weather and Climate

Weather

Observing and Recording the Weather

You will study different types of weather and find out how to measure them with weather instruments.
The study of weather is called metrology. There are several different types of weather that are observed on a day to day basis, these include:

  • TEMPERATURE – this is a measure of how hot or cold it is. Thermometers are used to measure temperature accurately.
  • PRECIPITATION – water in the air falls to the ground in several forms. Four of these are snow, rain, sleet and fog.
  • WIND SPEED – this tells you how strong the wind is. The Beaufort Scale is used to measure this.
  • WIND DIRECTION – this is the direction the wind blows FROM and is measured on a wind vane.
  • CLOUD TYPE – clouds come in many different shapes, sizes and heights. The most common types are cumulus (fluffy clouds), cumulonimbus (large clouds normally associated with thunderstorms), stratus (big blankets of cloud) and cirrus (wispy high clouds).
  • CLOUD COVER – this is the amount of the sky covered in cloud and is measured in eighths.
  • GENERAL WEATHER – this describes the weather in words. Words like sun, rain, snow, showers, fog etc are used.

Microclimates

You will take part in a piece of fieldwork on the topic microclimates, which will involve you measuring the weather at different places around Aylsham High School. The data you collect will be put into an assessed report of your findings.

Microclimates exist wherever the climate in a particular place is different to the general area. Some of the causes of microclimates are listed below:

  • PHYSICAL FEATURES – trees provide shade and shelter so are usually cooler than surrounding areas. If you stood on top of a hill, you would find it to be cooler and windier than at the bottom of the hill. Lakes and seas have a cooling effect and can produce light winds.
  • SHELTER – Trees, hedges, walls and buildings can provide shelter from the wind. Wind speed can be reduced and its direction changed, therefore making sheltered areas colder.
  • SURFACE – The colour of the ground causes small changes in temperature. If you touched the school playground it would be warmer compared to touching the school field. Dark surfaces (tarmac) will be warmer than light surfaces (grass).
  • BUILDINGS – buildings can cause microclimates in two ways; changing the temperature and reducing wind speeds. Buildings give off heat that has been stored during the day or which leaks from indoor heating systems. They can reduce wind speeds by a third.
  • ASPECT – this is the direction in which something is facing. Places that face the sun will be warmer.

Britain’s Weather

By comparing average monthly temperatures between July and January there are three main differences:

  • Temperatures are higher in the summer than in the winter.
  • Temperatures at any one time are not the same across the whole country.
  • The pattern of temperature is different in the two seasons. In July, the south is warmer than north but in January, the east is colder than the west.

There are five reasons for these differences in the weather and climate:

  • Wind direction because a north wind is cold and a west wind is moist.
  • Distance from the sea because the sea keeps the coast warm in winter but can cool them in the summer.
  • Temperatures are lowered in hills and mountains by 1 degree Celsius for every 100 m climbed.
  • An ocean current in the winter called the North Atlantic Drift raises the temperature in the west.
  • In the summer the sun warms the south more than the north.

Rainfall

Rain is part of a never-ending cycle called the water cycle. Water is evaporated from the sea and land, turns into clouds (by condensation), and falls as precipitation to the ground ready to evaporate again.

There are three types of rainfall you need to know; convectional, relief and frontal which are explained below:

  • CONVECTIONAL RAINFALL – The sun heats the ground which then warms the air above it causing currents of warm air to rise. As the air rises it cools and the water vapour condenses to form clouds and then rain. This causes showery and thundery weather in Britain.
  • RELIEF RAINFALL – When wind meets a line of high hills, it only has one way to go – up!. So the air rises and cools (down 1 degree Celsius for every 100m climbed. As it cools it condenses and forms clouds then rain. This type of weather common in the west on Britain.
  • FRONTAL RAINFALL – Two types of air mass exist; cold and warm. When a warm air mass meets a cold air mass the warm air slides over the cold one (because the colder one is heavier). The rising air cools and condenses to form clouds and then rain. This is the most common type of rainfall in Britain, especially in the winter.

Climate

In the climate section, you will look at climates from around the world and be able to understand how animals, vegetation and people adapt to the climate.

Mediterranean Climate

The Mediterranean has two very different seasons; the weather in the summer is hot and dry (temperature in July is 30 degrees Celsius) but in the winter it is warm and wet (temperature in January is 11 degrees Celsius). The summers are hot and dry because the sun rises high in the sky and the prevailing wind blows over the land (which is very hot and dry) bringing warm, dry air with it. Apart from the occasional thunderstorm, summers are cloudless and sunny. The winters are warm and wet because the sun is lower in the sky and the prevailing wind blows from the sea (which is warm and moist). This wind is forced to rise over coastal mountains causing relief rainfall.
Places that have this climate are normally found on the west coasts of continents and between the latitudes of 30 degrees and 40 degrees north and south of the equator.

Equatorial Climate

An equatorial climate causes it to be hot and wet all year round. Convectional rainfall is common most afternoons and there are no seasonal difference. The temperature is close to 30 degrees celsius all year and 1,800mm of rain falls each year. It is very hot because the sun is directly overhead all day long due to being close to the Equator. Places with an equatorial climate are within 5 degrees north or south of the Equator. The two main areas where it is found are the Amazon (South America) and Congo (Africa).
Tropical rainforest grow in areas with equatorial climate and the vegetation growing here have had to make several adaptions to cope with the hot, wet climate, these include:

  • EMERGENT TREES – trees grow over 40m high to get to the sunlight. This also causes trunks to be straight and branchless in there lower parts in there effort to get this tall.
  • DRIP TIPS – leaves are shaped to shed heavy rainfall.
  • LIANAS – vine like plants use large trees as a support to climb to the sun.
  • LITTLE UNDERGROWTH – this area is dark and damp. Sunlight cannot reach this level so only ferns can grow.
  • BUTTRESS ROOTS – large roots supporting tall trees.

Hot Desert Climate

The temperatures are very different in deserts between night and day. As hot deserts have very little cloud cover, the sun can easily heat the ground during the day so temperatures can rise to 50 degrees Celsius. However, at night the temperatures can drop to near freezing because there is no cloud to keep the heat in. The hot desert has two seasons; summers are hot while winters are much cooler (but not as cold as in Britain. The hot summers are caused by the sun being overhead which heats the land rapidly, being a long way from the cooling effect of the sea and the prevailing wind blowing over the warm land. The winters are cooler because the sun has shifted and is no longer overhead, being a long way away from the warming effect of the sea and the prevailing wind blowing over cool land. Places that have hot desert climates are found in the centre or west coasts on continents, between the latitudes 10 degrees and 30 degrees north or south of the Equator and where prevailing wind comes over dry land.

Plants and wildlife have had to adapt to be able to survive in these types of conditions. Only a few specially adapted plants survive, an example is the cactus. Adaptions of the cactus include:

  • Storing 8,000 litres of water at any one time.
  • Long but shallow roots to soak as much water as possible when it does rain.
  • Thick, waxy skin which reflects the suns heat and reduces moisture lost.
  • Not having leaves but spikes instead which help reduce moisture loss and stop animals from eating the plant.
  • A fleshy stem to store water.

Likewise camels are very well adapted to the climate. Adaptions of the camel include:

  • Being able to store water for long journeys.
  • Closing eyes, nose and mouth in a sandstorm.
  • Large pads on their feet for walking over sand and stones.
  • Tough, leathery mouths allow them to eat thorny plants that grow in the desert.
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