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Similar to Ch 2 GW 1 Slides (Part 1)
Ch 2 GW 1 Slides (Part 1)
- 1. Chapter 3 Weather &Climate Gateway 1
- 2. Describe the weather of Singapore over the last three days How would you describe the climate of Singapore?
- 3. How then is weather different from climate? What differen=ates weather from climate? MEASURE OF TIME – Weather: Short-‐term changes (minutes to months) – Climate: Long-‐term weather pa:erns (30 years)
- 4. What are the elements of weather? a. Temperature b. Relative humidity c. Clouds d. Rainfall e. Air pressure and wind
- 5. a. What influences temperature? (i) Latitude (ii) Altitude (iii) Distance from sea (iv) Cloud cover
- 6. (i) La>tude NorthPole 90°N longer distance through atmosphere shorter distance through atmosphere larger angle of incidence smaller angle of incidence atmosphere sun’s rays are concentrated over a smaller area sun’s rays are spread over a wider area South Pole 90°S Equator 0° Tropic of Cancer 23.5°N Tropic of Capricorn 23.5°S ∴ temperature becomes higher sun’s rays sun’s rays higher latitude lower latitude
- 7. (ii) Al>tude higherconcentration of atmospheric gases & particles to trap the heat emitted from the warm ground lesser atmospheric gases & particles to absorb heat incoming solar energy warms the earth’s surface earth’s atmosphere more concentrated nearer the earth’s surface longwave radiation from the ground earth’s atmosphere much thinner further from the earth’s surface
- 8. (ii) Al>tude 0m(ground) Base: larger area of land to absorb heat Peak: smaller area of land to absorb heat 1,000m 2,000m 3,000m 4,000m 5,000m (higher altitude) Altitude Temperature -13°C -6.5°C 0°C 6.5°C 13°C 19.5°Cdenser air thinner air Highland temp decreases by 6.5° with every 1000m increase in altitude
- 9. (iii) Distance from sea coastal areas SUMMER land heats up quickly sea heats up slowly cooler air over sea lowers the temperature of coastal areas air over sea becomes relatively cooler inland areas sea air over the land becomes warmer than the air over the sea inland areas experience warmer summers coastal areas experience cooler summers
- 10. (iii) Distance from sea coastal areas WINTER land cools quickly sea cools slowly warmer air over the sea increases the temperature of coastal areas air over the sea becomes warmer than the air over land inland areas sea inland areas becomes colder inland areas experience colder winters coastal areas experience warmer winters
- 11. (iii) Distance from sea coastal areas inland areas sea• land heats up quickly ➙ warmer summers • land cools quickly ➙ colder winters • sea heats up slowly • sea cools slowly causes larger annual temperature range in inland areas causes smaller annual temperature range in coastal areas cooler summers warmer winters
- 12. (iv) Cloud cover less solar radiation reaching the ground thick clouds absorb & reflect a large amount of incoming solar radiation back into space thick clouds absorb & prevent much of the heat that is radiated from the ground from escaping back into space Day (30°C) Night (25°C) earth’s surface is not heated up excessively in the day air near the earth’s surface is kept warm at night as temperature falls by only a few degrees Presence of cloud cover: smaller diurnal temperature range (less than 10°C)
- 13. (iv) Cloud cover heat radiated from the ground escapes back into space without interruption Day (40°C) earth’s surface becomes heated up excessively in the day air near the earth’s surface becomes cooler at night as temperature falls by many degrees maximum incoming solar radiation reaching the ground Night (10°C)Absence of cloud cover: diurnal temperature range as high as 30°C
- 14. a. What influences temperature? (i) Latitude (ii) Altitude (iii) Distance from sea (iv) Cloud cover C.L.A.D.
- 15. What are the elements of weather? a. Temperature (C.L.A.D.) b. Relative humidity c. Clouds d. Rainfall e. Air pressure and wind
- 16. b. Rela>ve humidity = Actual amount of water vapour in the air Maximum amount of water vapour the air can hold • RH is usually expressed in percentage (%) x 100 Maximum amount of water vapour the air can hold Actual amount of water vapour in the air at a par>cular >me (T1) At 15°C 10g/m3 5g/m3
- 17. Where does water vapour in the air come from? Evaporation froM: • ponds, lakes • seas, oceans • water on leaves Transpiration froM: • vegeta>on
- 18.
- 19. How does the amount of water vapour affect the rela=ve humidity? Maximum amount of water vapour the air can hold Actual amount of water vapour in the air at T1 At 15°C Actual amount of water vapour in the air at T2 10g/m3 5g/m3 8g/m3 ✏ The higher amount of water vapour in the air at a par7cular temperature, the higher the rela7ve humidity.
- 20. Let’s put the same mass of air (5g/m3) at different temperatures: Maximum amount of water vapour the air can hold Actual amount of water vapour in the air at T1 At 15°C 10g/m3 5g/m3 At 25°C Maximum amount of water vapour the air can hold Actual amount of water vapour in the air at T3 20g/m3 5g/m3 ✏ Lowest RH occurs during 7me of greatest air temp
- 21. Why do I feel more humid on a rainy day? At 25°C 20g/m3 Actual amount of water vapour in the air after the rain (T4) Maximum amount of water vapour the air can hold Actual amount of water vapour in the air before the rain (T3) 5g/m3 At 15°C 20g/m3 ✏ Satura>on occurs when RH = 100% ✏ The temp at which satura>on occurs is called the dew point temperature
- 22. What are the elements of weather? a. Temperature b. Relative humidity c. Clouds d. Rainfall e. Air pressure and wind
- 23. c. Clouds ③ When water droplets in the air bump into each other, they coalesce and become larger to eventually form clouds. Dew point reached: condensation begins ① As water vapour rises, it cools. Eventually, rising air cools to dew point temperature. The tiny particles (eg. dust) in the air are called condensation nuclei. ② Water vapour condenses on tiny particles present in the atmosphere to form water droplets. ground ④ When the water droplets become too large & heavy, they fall to the earth’s surface as precipitation (eg. rain, hail)
- 24. c. Clouds Interes>ng clouds
- 25. What are the elements of weather? a. Temperature b. Relative humidity c. Clouds d. Rainfall (convectional & relief rain) e. Air pressure and wind
- 26. d. Rainfall Dew Mist Fog Rain Hail Snow different types of Precipitation main form of precipita7on in the tropics
- 27. d. Rainfall measureusing: – a rain gauge (in mm) High rainfall: – more than 1,500mm Low rainfall: – less than 250mm
- 28. d. Rainfall instableair: – it is a parcel of air that rises instead of remaining in its original posi>on • Hot air rises (unstable) • cool air sinks caused by air instability
- 29. d. Rainfall Tempof air parcel1 = 9.5 °C Distance away from the ground Temperature of surrounding air 100m 10°C 9.3°C Parcel of air sinks and remains near the ground because it is cooler than its surrounding air ➙ it is a stable air parcel Parcel of air expands and rises as it is warmer than its surrounding air ➙ it is an unstable air parcel 0m (ground) Temp of air parcel2 = 10.5 °C Temp of air parcel2 = 9 °C The parcel of air stops rising & remains at this position because it is now cooler than its surrounding air ➙ it becomes a stable air parcel • Hot air rises (∴unstable) • Cool air sinks (stable) Stable & unstable air parcels
- 30. d. Rainfall ① Earth’s surface is intensely heated up by the sun’s energy ② Air above the ground warms, expands & rises. ③ As water vapour rises, it cools. Eventually, air cools to dew point temperature. ④ Cumulonimbus clouds are often formedDew point reached: condensation occurs ➙ clouds form ⑤ Water droplets in the clouds eventually become too large and heavy. Thus, they fall to the ground as convectional rain. Such rain is usually accompanied by thunder & lightning. #1 Convectional rain
- 31. d. Rainfall #2relief rain Mountain barrier ① Moist air from the sea is forced to rise up the windward slope. ② As air rises, it cools to the dew point temperature. Thus, condensation occurs & clouds form. ③ When water droplets in the clouds become too large and heavy, they fall as relief rain. ④ By the time the air moves down the leeward slope, it is dry as most of the moisture has fallen on the windward side. Thus, no rain falls on the leeward side. h:ps:// www.youtube.com/ watch?v=BVykQfRC_aI
- 32. What are the elements of weather? a. Temperature b. Relative humidity c. Clouds d. Rainfall (convectional & relief rain) e. Air pressure and wind
- 33. e. Air pressure and winds Air pressure: – force exerted on a unit area of the earth’s surface caused by the weight of a column of air above it. Air pressure @ sea level: – 1,013millibars (mb) High air pressure: – if above sea value (ie. more than 1,013mb) Low air pressure: – if below sea value (ie. less than 1,013mb)
- 34. e. Air pressure and winds ∴ sea level (1,013mb) Altitude denser air (∴ higher air pressure) less dense air (∴ lower air pressure) Highland higher altitude (200mb) larger column of air ∴ higher pressure Air is less dense at higher altitudes because gravity pulls air molecules towards the surface of the earth. lower altitude (1,000mb) smaller column of air over a unit area
- 35. e. Air pressure and winds measure pressure using: – a barometer (in mb) – millibars
- 36. e. Air pressure and winds Isobars – lines joining places of equal air pressure Weather map / synoptic chart – constructed using measurements of air pressure
- 37. e. Air pressure and winds High air pressure: – pressure more than 1,013mb Low air pressure: – pressure less than 1,013mb Air moves from High to low pressure areas
- 38. e. Air pressure and winds pressure gradient – difference in air pressure between 2 loca>ons wind: – movement of air from high pressure to low pressure areas wind speed: – rate at which air is moving Faster wind speed: – when there is a greater difference in air pressure
- 39. e. Air pressure and winds measure wind speed using: – an anemometer (in km/hr)
- 40. e. Air pressure and winds wind systems – Sea & land breezes: • Sea breeze (day) • Land breeze (night) – Monsoon winds: • Southwest monsoon (between Jun & Sep) • Northeast monsoon (between Oct & Feb)
- 41. e. Air pressure and winds Sea and Land Breeze: – formed by the differences in air pressure due to the different rates at which land and water bodies cool: • Landà heats up & cools down quickly • Seaà heats up & cools down slowly h:p://www.classzone.com/books/earth_science/ terc/content/visualiza>ons/es1903/ es1903page01.cfm?chapter_no=visualiza>on
- 42. e. Air pressure and winds Monsoon winds: – large scale seasonal winds that reverse direc>on seasonally – causes seasonal changes in precipita>on – monsoon winds & other winds are affected by Coriolis effect
- 43. e. Air pressure and winds Coriolis effect: – a force produced by earth’s rota>on – it causes the bending or deflec7on of winds: • northern hemisphere wind deflects right • southern hemisphere wind deflects le< – it is strongest @ the poles; – it is weak @ the tropics; and – it is not felt @ the equator
- 44. e. Air pressure and winds Equator 0° 30°S 30°N 60°N 60°S South Pole 90°S North Pole 90°N (low pressure) (high pressure) (high pressure) (low pressure) (low pressure) (high pressure) (high pressure) Air moves from a zone of high pressure to low pressure
- 45. e. Air pressure and winds Equator 0° 30°S 30°N 60°N 60°S South Pole 90°S North Pole 90°N In the northern hemisphere, winds are deflected to the right due to the coriolis effect In the southern hemisphere, winds are deflected to the left due to the coriolis effect (low pressure) (low pressure) (low pressure) (high pressure) (high pressure) (high pressure) (high pressure)
- 46. e. Air pressure and winds Monsoon winds: – caused by the different rates of hea>ng up & cooling down of huge land masses & seas – this creates difference in air pressure between land masses & seas – this results in the movement of large-‐scale winds from high pressure to low pressure areas
- 47. What are the elements of weather? a. Temperature b. Relative humidity c. Clouds d. Rainfall (convectional & relief rain) e. Air pressure and wind T.R.R.A.C.