Weather and Climate 1

1. Weather and Climate 1 Whether it is climate or not?

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

3. What is the weather? Weather is the condition of the air around us over a short period of time (from day to day)

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

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

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

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

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

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

10. 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)

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

12. Measuring Weather Who else might find a forecast useful? • 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?’

13. Measuring temperature • The 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.

14. A Stevenson screen Why do we need one of these? What are the little gaps in the side for? (louvers) Why does it have legs? Why is it painted white? Why has it got such a large roof?

15. Measuring 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.

16. Measuring Temperature • This 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 thermometer • There 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.

17. Measuring Temperature • The temperature tends to be highest around the middle of the day, when the sun is at its hottest – even if you cannot see it because it is cloudy • The temperature is coldest during the night • So 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) • The difference between the daily maximum and the daily minimum temperature is the diurnal range.

18. Looking at the first 2 rows on the 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?

19. Wind speed • Wind 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 speed can be recorded in many different units, including for example: • miles per hour; • kilometres per hour; • metres per second; • knots; • 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?

20. Wind direction • The 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 simply holding a light object such as a flag or ribbon. • On your sheet, write down what they are smelling!! • http://www.bbc.co.uk/schools/whatisweather/aboutweather/winddir.shtml

21. Wind direction • Knowledge 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-off • Wind 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

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

23. Air pressure • An 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

24. Air pressure • Why 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 winter • Low pressure gives us cloudy skies and rain. We have lots of low pressure over the summer in the UK!

25. For the WS • What 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?

26. Measuring liquid precipitation • 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?

27. This is the rain gauge used by the 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?

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

29. Weather is important to us • Things that are affected by weather • farming • sport • transport • the amount of energy we use • work • tourism

30. So we need weather forecasts • Information is collected by • weather stations • http://www.weatherstations.co.uk/aws_map.htm • Often schools have them

31. So we need weather forecasts • Information is also collected by • By ships • Aircraft • Satellites • and then the meteorologists use the information they have to predict the weather over the next few days

32. Weather from the met office • Friday’s map from • http://www.met-office.gov.uk/weather/europe/uk/uk.html

33. Weather from the met office • This was the wind map. The numbers measure in miles per hour with direction it is blowing to • http://www.met-office.gov.uk/weather/europe/uk/uk.html

34. Weather from the met office • This was the Temperature map. The numbers measure in degrees centigrade • http://www.met-office.gov.uk/weather/europe/uk/uk.html

35. And BBC weather From http://www.bbc.co.uk/weather/ukweather/index.shtml It used to show it all on but now they just show where the cloud is!!

36. And weather online From http://www.weatheronline.co.uk Does show it all except the wind speed and direction!!

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

38. Go to (hopefully now!) http://www.weatheronline.co.uk/ Click either UK or your continent If it is the UK, click on your region Do not go more detailed than that If a continent, pick which part, then pick your country Homework

39. I clicked on Africa Southern Africa South Africa and I saw this But I don’t want today – I want Wednesday to Sunday The other days are tabs above the maps I am doing South Africa for Toby

40. You do need to label the days – it does not come up with it if you use right click and copy image

41. Now you have got your weather forecast • 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 table • Record the weather you had in the middle column

42. Now you have got your weather forecast • 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…’. Remember what we said about comparing things • For example: • I thought the weather forecast was completely wrong. This is because the forecast said it would snow when really there was mostly sunshine with a few clouds.