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# Weather elements unit 15

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### Weather elements unit 15

1. 1. Unit 15: Weather Elements Objectives Differentiate between weather and climate. Understand the use and siting of the weather instruments.
2. 2. Weather • Weather describes the condition of the atmosphere of a place over a short period of time. • Temperature, rai nfall and wind Climate • Climate is the average conditions of the atmosphere of a place over a long period of time. • Average temperature and average rainfall pattern is used.
3. 3. Is this weather or climate data?
4. 4. Is this a weather or climate data? Climatic maps are used to show information such as distribution of temperature and rainfall of a country, region or the world.
5. 5. Thermometer • Temperature refers to the degree of heat in the air. It tells us how hot or cold the air is. • A thermometer is used to measure temperature in degree Celsius (◦C) or degree Fahrenheit(◦F). • Six’s Thermometer or the maximum and minimum thermometer is used to record the highest and lowest temperatures of a day.
6. 6. Six’s thermometer
7. 7. • Made up of Mercury and Alcohol • Mercury – Very high boiling point • Alcohol – Very low freezing point • Read off the base of the Indices (Indicators)
8. 8. Activity - Reading the Six’s Max = 30 oC Min = 5 oC Mercury Metal Indices Alcohol Max = 20 oC Min = 10 oC Max = 7.5 oC Min = -15 oC
9. 9. Stevenson Screen • The Six’s thermometers are placed in a white, wooden box called a Stevenson Screen. • White wooden box to reflect heat • Louvred sides to allow air to flow freely • Doubled layered roof to prevent direct heating from the sun • Stand on stilts to prevent heat from the ground to be trapped
10. 10. Calculating Temperatures (1/5) Daily temperature Range = Maximum Temp - Minimum Temp For example Max temp = 30 oC Min Temp = 10 oC Daily temp range = 20 oC
11. 11. Calculating Temperatures (2/5) Mean (average) daily temperature = Maximum Temp + Minimum Temp 2 For example Max temp = 30◦C Min Temp = 10◦C Average daily temp= (30+10)/2 = 20◦C
12. 12. Calculating Temperatures (3/5) Mean (average) monthly temperature = Total average daily temp for the month Number of days in the month
13. 13. Calculating Temperatures (3/5) Mean (average) monthly temperature = Average max temp + Average min temp 2 Only used this when average maximum and average minimum temperature are given.
14. 14. Calculating Temperatures (4/5) Mean (average) Annual temperature = Total average monthly temp in a year 12
15. 15. Calculating Temperatures (5/5) Annual temperature range = Highest mean - Lowest mean monthly temp monthly temp
16. 16. Location X Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Temp 23 22 20.5 16.5 14 10.5 10 11 12.5 14 17.5 21 Mean Annual Temperature = Total of mean monthly temperature / 12 = (23 + 22 + 20.5 + 16.5 + 14 + 10.5 + 10 + 11 + 12.5 + 14 + 17.5 + 21 ) / 12 = (192.5) / 12 = 16.04 oC Annual Temperature Range = Highest Temperature – Lowest Temperature = 23 – 10 = 13 oC
17. 17. Location Y Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Temp 25.5 26 26.5 27 27.5 28 27.5 27 26.5 26.5 26 26 Mean Annual Temperature = Total of mean monthly temperature / 12 = (25.5 + 26 + 26.5 + 27 + 27.5 + 28 + 27.5 + 27 + 26.5 + 26.5 + 26 + 26 ) / 12 = (321) / 12 = 26.75 oC Annual Temperature Range = Highest Temperature – Lowest Temperature = 28 – 25.5 = 2.5 oC
18. 18. • Average daily or mean daily temperature: • Calculation of temperature data: Temperature Average daily or mean daily temperature Maximum temperature + Minimum temperature 2 = Daily temperature range Maximum temperature - Minimum temperature= Average monthly temperature Sum of average daily temperatures for the month Number of days in the month = Average annual temperature Sum of average monthly temperatures in a year 12 = • Daily temperature range • Average monthly temperature • Average annual temperature
19. 19. •An instrument used to measure the amount of rainfall •Rain falls through a funnel and is collected in the bottle •Excess rain that overflows is collected in the copper cylinder •Amount of rain collected is poured into a measuring cylinder, calibrated in millimeters • Rain gauge: Rainfall outer cylinder funnel glass bottle measuring cylinder copper cylinder
20. 20. •One-third of the rain gauge is sunk into the ground to prevent toppling •To be placed in an area free of obstructions •Rain gauge: Rainfall copper cylinder funnel glass bottleouter cylinder
21. 21. Calculating Rainfall (1/4) Daily rainfall = Sum of all rainfall readings in a day
22. 22. Calculating Rainfall (2/4) Monthly rainfall = Sum of all daily rainfall readings in a month
23. 23. Calculating Rainfall (3/4) Total annual rainfall = Sum of the total monthly rainfall received for the year.
24. 24. Calculating Rainfall (4/4) Mean (average) monthly rainfall = Total annual rainfall 12
25. 25. • Horizontal movement of air from a high pressure area to a low pressure area • Associated with land and sea breezes Wind wind high pressure low pressure cold air sinkswarm air rises land Sea
26. 26. Wind •In the day, air over the sea is cooler than that over the land, thus the cooler air sinks, creating a higher pressure area. •Warmer air over the land rises, creating a low pressure. •Differences in pressure cause the air over the sea to move towards the low pressure over the land. •This horizontal movement of air causes wind. NOTE: Greater differences in pressure give rise to stronger breezes.
27. 27. •The wind vane points to the direction where the wind is blowing from •It is made up of a freely moving pointer and four cardinal points – north, south, ea st, west • Measuring wind direction: Wind vane
28. 28. •The wind rose records the wind direction. •It is represented by a centre circle and eight arms representing the main eight compass directions. •The number of calm days is recorded in the centre circle. •The longer the arms, the more days the wind is received from that direction. Wind rose 5 E S N NW SW NE number of calm days5
29. 29. • Siting of weather instruments: Wind Stevenson screen • 120cm above ground level • Six’s thermometer is kept inside • insulated from heat by material and design rain gauge • 30cm above ground level • on short grass away in an open field from buildings wind vane • top of the meteorological station with no obstructions
30. 30. 5 meteorological/weather stations in Singapore