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What are the different types of What are the different types of weatherweather

How do we

measure weather?

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Today we will look at …Today we will look at …1. What makes weather?2. How do we measure weather?3. Why do we need forecasts?4. Are the forecasts any good? (that’s

homework)

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What is the weather?What is the weather?

Weather is the condition of the air around us over a short

period of time (from day to day)

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The elements of weather The elements of weather Temperature (the amount of heat) Precipitation (water – rain, sleet, hail, snow)Wind speed Wind direction CloudsAir pressure Visibility (How far can you see?)

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Temperature Temperature This is a measure of how hot or cold it is. We can tell this by looking at the clothes that people wear.

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Precipitation Precipitation Water in the air falls to the ground in one of several forms Rain Snow Sleet Hail But also ice and fog

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Wind Speed Wind Speed

This tells us how strong the wind is. We can get a good ideas of this by looking at smoke and trees.

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Wind direction Wind direction This is the direction from which the wind blows – it is measured by a wind vane

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Cloud Type Cloud Type Clouds come in many shapes, sizes and heights – more about that next week

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Cloud Cover Cloud Cover This is the amount of the sky covered by cloud. It is measured in eighths

Clear sky

4/8

8/8 (Total cover)

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Visibility Visibility This is the distance that can be seen. It is measured in metres.

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Measuring Measuring WeatherWeather

Why do we measure the weather? Weather can be described using terms such as wet or fine, warm or cold, windy or calm, so why is there a need to measure the weather? For most people, a description of the weather is adequate but for many businesses more detailed and accurate measurements are required. The science of studying weather is called meteorology. Weather scientists or meteorologists measure temperature, rainfall, pressure, humidity, sunshine and cloudiness and they make predictions and forecasts about what the weather will do in the future. This is important for giving people advance notice of severe weather such as floods and hurricanes – or even ‘Can I go out without my raincoat tomorrow?’

Who else might find a forecast

useful?

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Measuring temperatureMeasuring temperatureThe hotness or coldness of a substance is called its temperature and is measured with a thermometer. The ordinary thermometer consists of a hollow glass bulb attached to a narrow stem with a thread-like bore. The bulb is filled with liquid, – If it is silver it is mercury– If it is red it is alcohol

The liquid in the tube expands when the temperature rises and contracts when the temperature falls. The amount of expansion and contraction is measured by a numbered scale.Whilst thermometers are really measuring their own temperature, they are used to measure the temperature of the surrounding air. To make sure that the temperature of the surrounding air is the same as the thermometer, it must be shaded from sunlight and be exposed to adequate ventilation. These conditions are provided by a Stevenson screen.

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A Stevenson screenA Stevenson screenWhy do we need one of

these?

Why does it have legs?

Why is it painted white?

Why has it got such a large roof?

What are the little gaps in the side

for?(louvers)

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Measuring temperatureMeasuring temperature

Most temperature scales today are expressed in degrees Celsius (°C), although you will sometime see Fahrenheit (°F) in use. The Celsius scale is fixed by two points, the freezing and boiling point of water, which at sea level are 0°C and 100°C respectively. The scale is then divided into 100 units.

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Measuring TemperatureMeasuring TemperatureThis is a maximum-minimum thermometer. This type of thermometer measures both the highest (maximum) and lowest (minimum) temperature over a period of time, usually one day (24 hours).Recording temperature with a maximum-minimum thermometerThere are two markers, one for the maximum temperature and one for the minimum. The mercury in the tube pushes the markers as temperatures go up or down.

The temperature tends to be highest around the middle of the day, when the sun is at its highest in the sky – even if you cannot see it because it is cloudyThe temperature is coldest during the nightSo if you leave a maxi-min thermometer for 24 hours you will get the maximum and the minimum and be able to find the daily range (the difference between the 2) or the diurnal range.

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Looking at the first 2 rows on Looking at the first 2 rows on the WSthe WS

What does a thermometer do?How does it work?What does a maxi-min thermometer tell you?What is diurnal range?What does a Stevenson screen do?How does it work?

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Wind speedWind speedWind is moving air. Wind can be measured by its speed and the direction from which it has come. The speed of the wind can be measured using a weather instrument called an anemometer. The number of turns it does is translated into speed which can be recorded in a number of different ways:– miles per hour; – kilometres per hour; – metres per second; – Knots ( a measurement sailors use) – the Beaufort Scale (we will learn about

this one next week)

This one has a

weather vane on it

underneath. What does

that tell you?

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Wind directionWind directionThe direction of the wind is expressed as the point on the compass from where the wind is blowing. If a wind is blowing from the south, it is travelling northwards but is called a southerly wind. Wind direction can be measured in many different ways; using a weather vane or windsock or simply holding a light object such as a flag or ribbon. http://www.bbc.co.uk/schools/whatisweather/aboutweather/winddir.shtml

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Wind directionWind directionKnowledge of wind direction is important for many people and activities. For example aircraft need to take off from the end of the runway which is going into the wind for extra lift at take-offWind direction is of course very important for leisure activities such as yachting. Can you think of anything else where knowing the wind direction is important?

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For the WS…For the WS…What is an anemometer for?How does it work?What is a weather vane for?How does it work?

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Air pressureAir pressureAn instrument called a barometer is used to measure the pressure of air. Although air is very light, because the atmosphere is so thick (many kilometres in altitude above the Earth's surface), air exerts a force or pressure. When air is cooled it sinks towards the ground, the pressure increases and a high pressure is measured. When the air warms up it rises, the pressure is reduced and low pressure is measured.

This is what goes on inside a barometer

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Air pressureAir pressureWhy do we need to know about pressure?High pressure gives us clear skies which means it is hot in the summer and cold in the winterLow pressure gives us cloudy skies and rain. We have lots of low pressure over the summer in the UK!

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For the WSFor the WSWhat is a barometer for?How does it work?What is weather like if the pressure is high in summer?What is the weather like if the pressure is low?

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Measuring liquid Measuring liquid precipitationprecipitation

What varieties of precipitation are there?Which types are NOT liquid?Why do you think that if we measured this one, that we might not use the same instrument as the liquid one?

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This is the rain gauge used by This is the rain gauge used by the Met Officethe Met Office

Why do you think the actual funnel is

inside a copper cylinder – not a the

top?

Why is the bottle that stores the

water underground?

How does the measuring gauge on the right work?

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For the WS…For the WS…What is a rain gauge for?What kind of precipitation does it not collect?

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Weather is important to usWeather is important to usThings that are affected by weather– farming– sport– transport– the amount of energy we use– work– tourism

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So we need weather So we need weather forecastsforecasts

Information is collected by– weather stations– http://www.weathers

tations.co.uk/aws_map.htm

Often schools have them

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So we need weather So we need weather forecastsforecasts

Information is also collected byBy shipsAircraftSatellitesand then the meteorologists use the information they have to predict the weather over the next few days

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Symbols are different but once you get the idea…So what is the weather supposed to be like in each of these places?

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HomeworkHomework

Go to (hopefully now!)http://www.weatheronline.co.uk/ Click either UK or your continent

If it is the UK, click on your regionDo not go more detailed than thatIf a continent, pick which part, then pick your country

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I am doing South I am doing South Africa Africa

I clicked on Africa on previous link and got this: I clicked on Southern Africa and got the dropdownThen I clicked on South Africa and saw this:

But I don’t want today – I want the next 5 days which are tabs above the maps.This one shows a Monday, so I would copy and paste Tuesday to Saturday.So if I click on Tuesday, hover over the map, right-click and copy image, you can then paste it into the homework document.

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Now you have got your weather Now you have got your weather forecastforecast

Look out each day – how good was the forecast?If you have a thermometer, do use it and add that information in!If you haven’t, not to worry.Having put your pictures into the tableRecord the weather you had in the middle column

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Now you have got your weather Now you have got your weather forecastforecast

In the last column, comment on whether the weather forecast was completely rubbish, pretty good or spot on – Remember to give your opinion and then add a ‘because…’. For example:The weather forecast was completely wrong, becausebecause the forecast said it would snow when really there was mostly sunshine with a few clouds.