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Variable weather n changing climate (1)

  1. 1. VARIABLE WEATHER & CHANGING CLIMATE 1. Why do different places experience different weather and climate? 2. What is happening to the Earth’s climate? Copy when you see:
  2. 2. IMPORTANT NOTE • For unit 2, Weather –Please bring your text book, we are using the exercises inside.
  3. 3. THINK ABOUT THIS… GATEWAY 1: Why do different places experience different weather and climate? • Why does Singapore not have any snow? • How does knowing the weather the next day help you to plan your activities? • Why does it always feel so warm in the evening despite the temperature falling? • Why does it rain so often in Nov/Dec? • More questions from you?
  4. 4. Elements of Weather • Temperature • Relative Humidity • Clouds • Rainfall • Pressure and Winds
  5. 5. TEMPERATURE • Measures the degree of hotness or coldness • Energy of sun -> Travels through atmosphere -> Absorbed by earth’s surface -> Surface warms up -> Heats up atmosphere • Temperature measurement = oC • Maximum and minimum temperature • Diurnal temperature range • Mean daily/monthly/annual temperature • Annual temperature range
  6. 6. Maximum and minimum temperature • The highest and lowest temperatures recorded within a day. • Normally affected most by the presence or absence of sunlight (key heatsource)
  7. 7. Diurnal Temperature • The difference between the Maximum and minimum temperature of the day. January 1 2 3 4 5 6 7 8 9 10 11 12 Maximum 26 27 27 26 28 28 28 28 29 29 27 25 Minimum 25 25 25 24 25 25 24 25 25 26 26 24
  8. 8. Mean annual temperature • The average of all the monthly average temperatures • Sum of all divided by 12 months. Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec COUNTRYC -30 -28 -25 -20 -16 -15 -10 -16 -22 -29 -30 -35 COUNTRYD 27 27 28 28 29 30 32 30 30 29 28 28
  9. 9. Annual Temperature Range • The variation of temperature between the monthly average temperature readings. • Difference between the highest and lowest recorded temperatures.
  10. 10. Land Breeze • Coastal effect experienced at night • Sea retains heat better at night, air parcel above the sea is warmer. • Warmer air rises up, leaving a vacuum. • The cooler air above the land rushes out to the sea. • This movement of air from land to sea forms the land breeze
  11. 11. Land Breeze Diagram
  12. 12. Sea Breeze • Coastal effect experienced in the day • The air above the land heats up faster than the air above the water. • Warmer air rises up, leaving a vacuum. • The cooler air above the sea rushes into the land. • This movement of air from sea to land forms the sea breeze
  13. 13. Sea Breeze Diagram
  14. 14. TEMPERATURE • Temperature can be affected by: – Latitude – textbook page 75 – Altitude – textbook page 76 – Distance from the sea – textbook page 77 – Cloud cover – textbook page 77
  15. 15. Latitude
  16. 16. Altitude
  17. 17. Distance from sea
  18. 18. Cloud coverage
  19. 19. FACTORS AFFECTING TEMPERATURE • Maritime Effect – The effect of large ocean bodies on climate of coastal areas – During summer the air over the sea remains cooler than the land as it heats up slower – During winter the air over the sea remains warmer than the land as it loses heat slower – This causes coastal areas to have cooler summers and warmer winters – The annual temperature range is thus smaller
  20. 20. FACTORS AFFECTING TEMPERATURE • Latitude – Imaginary horizontal lines running east to west – Equator = 0o – North / South Pole = 90oN / 90oS – Angle of incidence: refers to the sun’s rays hitting the earth surface at an angle – A higher angle of incidence means more concentrated sunlight
  21. 21. FACTORS AFFECTING TEMPERATURE • Altitude – Refers to the height of a location in relation to the sea level – Temperature decreases with altitude – The higher the altitude, the lower the temperature – Earth’s atmosphere is mostly heated by the surface – Shortwave radiation: sun’s solar energy reaching the earth’s surface – Longwave radiation: Earth’s surface emitting heat to heat up the atmosphere
  22. 22. FACTORS AFFECTING TEMPERATURE • Altitude – Density of air becomes lower as altitude becomes higher – Dense air absorbs more longwave radiation – Air that is less dense at higher altitudes absorb less heat and thus temperature is lower – Qn: Name some gases that would absorb heat.
  23. 23. FACTORS AFFECTING TEMPERATURE • Distance from the sea – The sea always heats up and cools down more slowly than land – This creates differences in rate of heating between coastal and inland areas – Places that are located along the coasts experience Maritime effect – Places that are located further inland experience Continental effect
  24. 24. FACTORS AFFECTING TEMPERATURE • Continental Effect – The effect of continental surfaces on climate of inland areas – Inland areas are further from the sea and oceans – These areas are not influenced by the temperatures over the sea – Inland areas tend to have warmer summers and colder winters – The annual temperature range is thus larger
  25. 25. FACTORS AFFECTING TEMPERATURE • Cloud cover – Refers to the extent of sky that is covered by clouds – More cloud cover results in a smaller diurnal range – Less cloud cover results in a larger diurnal range – This is due to the effect of clouds absorbing and reflecting the sun’s rays and heat energy from the earth’s surface (pg 77, fig 2.9)
  26. 26. TEMPERATURE • DISCUSS – Qn: Why do different places along the same latitude have different temperatures? • EXERCISE – Textbook page 79 – Questions 1, 3 and 6 Group Work Groups of 5 please
  27. 27. RELATIVE HUMIDITY RELATIVE HUMIDITY = Actual amount of water vapour in the air --------------------------------------------------------------- X 100 Max amount of water vapour the air can hold
  28. 28. RELATIVE HUMIDITY • Relative humidity is the ratio between the actual amount of water vapour and the maximum amount of water vapour that the air can hold at a given temperature • Warmer air can hold more water vapour • If temperature rises and the actual amount of water vapour remains, then relative humidity will decrease
  29. 29. RELATIVE HUMIDITY • Saturation is when relative humidity = 100% • Dew point temperature: temperature at which saturation occurs • Condensation occurs during dew point temperature
  30. 30. CLOUDS • Clouds refer to visible masses of water droplets or ice crystals suspended in the atmosphere • Evaporation: water becoming water vapour • When water vapour rises, it cools to dew point temperature • Condensation: water vapour changes to liquid form • To condense, water vapour needs to find condensation nuclei • Coalescence: water droplets bumping into each other to become larger in size
  31. 31. Cloud making experiment • We’ll do an experiment now to make clouds • Let’s recap the key elements of a cloud. – Water vapour – Rapid condensation – Pressure loss
  32. 32. Let’s watch the clip first
  33. 33. Let’s do it ‘live’ • Equipment check 1. Plastic bottle 2. Rubbing alcohol 3. Bicycle pump
  34. 34. Recap • Sudden condensation leads to formation of clouds by water vapour. • Clouds are liquid form of water that have condensed. • If there is added pressure, the water vapour reverts to it’s gaseous form.
  35. 35. RAINFALL • Precipitation: water falling from the atmosphere to the earth surface in any form • E.g. Hail, Snow, Sleet, Rain… • In tropics, the precipitation is mainly rain • Air stability: a parcel of air that is cooler than its surrounding air and tends to sink and remain in its original position • Air instability: a parcel of air that is warmer than its surrounding air and tends to rise and expand • 2 types of rainfall: Convectional and Relief
  36. 36. RAINFALL • Convectional Rain – Occurs due to intense heating of earth’s surface – Warm surface heats the air above it – Instability causes air to rise and expand – As air rises, it cools to dew point temperature – Condensation occurs and clouds are formed – When water droplets become large enough, they fall as rain – Convectional rain is often associated with lightning and thunder – Intense rain over a short amount of time
  37. 37. RAINFALL • Relief Rain – Also known as Orographic rain – As air passes over the sea, it picks up moisture – When it arrives at the coast, moist air is forced to rise along the windward side of the mountain – Air is forced to cool and condensation occurs at dew point temperature – When water droplets in the clouds become heavy enough they fall to the ground on the windward side – On the other side of the mountain, leeward side, it is dry as most of the moisture is lost on the windward side (rain shadow)
  38. 38. RELATIVE HUMIDITY, CLOUDS & RAINFALL • DISCUSS – What is the most common type of rainfall in Singapore? Why do you say so? • EXERCISE – Textbook page 82 – Questions 1, 2, 3 and 5
  39. 39. PRESSURE & WINDS • Air pressure: the forced exerted by the weight a column of air on a unit area of the earth’s surface • Measured in millibars (mb) by a barometer • Air is less dense at higher altitudes • Thus air pressure tends to be lower as altitude increases • The average value of air pressure at sea level is 1,013mb
  40. 40. PRESSURE & WINDS • Wind: The movement of air from high pressure area to low pressure area • Pressure gradient: The difference in air pressure between two places • The greater the pressure gradient, the higher the wind speed • Wind can be described by its speed, direction and frequency.
  41. 41. PRESSURE & WINDS • Wind speed: The rate at which air is moving • Wind speed is measured in kilometres per hour, using an anemometer • Wind speed may also be represented by the Beaufort Scale (pg 85, figure 2.23)
  42. 42. PRESSURE & WINDS • Wind direction: The direction which the wind blows from • Wind direction is measured by a wind vane • Wind frequency: The percentage of time the wind blows from a particular direction • Prevailing winds: Winds that blows most frequently from a specific direction • Information of wind direction and frequency can be recorded using wind roses
  43. 43. PRESSURE & WINDS • Wind systems is a way of categorising prevailing winds • Localised wind systems – Land breeze – Sea breeze • Regional wind systems – Monsoon Winds – Mid-latitude Westerlies – Polar Easterlies
  44. 44. PRESSURE & WINDS Land and Sea Breezes • Local wind systems that occur along coastal areas due to different rates of heating between the land and sea • Recall how temperature is affected by distance from the sea • In the night – Land loses heat faster than the sea – Warm air above the sea rises, creating low pressure – Air from the land moves towards the sea as land breeze
  45. 45. PRESSURE & WINDS Land and Sea Breezes • In the day – Land heats up faster than the sea – Warm air above the land rises, creating low pressure – Air from the sea moves towards the land as sea breeze
  46. 46. PRESSURE & WINDS Monsoon Winds • A regional wind pattern • Brings seasonal changes in precipitation • Affected by Coriolis effect • Northern hemisphere -> deflects to the right • Southern hemisphere -> deflects to the left • Coriolis effect is stronger nearer the poles and weaker near the equator
  47. 47. PRESSURE & WINDS Monsoon Winds • For purposes of study, we will use the monsoon winds blowing between Asia and Australia as an example • You should keep the following background knowledge that you ALREADY HAVE… – Summer = Higher Temp, Winter = Lower Temp – High Temp = Low pressure, Low Temp = High pressure – Concept of relief rain and rain shadow – Coriolis Effect: North = Right and South = Left • Are you ready?
  48. 48. PRESSURE & WINDS Southwest Monsoon (pg 88, figure 2.26) • June to September • Summer in northern hemisphere, winter in southern hemisphere • Winds move from Australia (south) to Asia (north) • From Australia, wind moves as southeast monsoon • As it crosses the equator, it deflects to become southwest monsoon • The air picks up moisture over Indian Ocean and brings heavy rain to India
  49. 49. PRESSURE & WINDS Northeast Monsoon (pg 88, figure 2.27) • October to February • Summer in southern hemisphere, winter in northern hemisphere • Winds move from Asia (north) to Australia (south) • From Asia, wind moves as northeast monsoon • As it crosses the equator, it deflects to become northwest monsoon • The air picks up moisture over Indian Ocean and brings heavy rain to Australia
  50. 50. PRESSURE & WINDS • DISCUSS – How does the NE and SW monsoon winds affect Singapore in terms of rainfall? • EXERCISE – Textbook page 89 – Questions 2 and 4
  51. 51. CLIMATIC SYSTEMS • Blah blah
  52. 52. THINK ABOUT THIS… GATEWAY 2: What is happening to the earth’s climate? • Why are we so concerned about carbon footprints? • blahblah • More questions from you?

Editor's Notes

  • Run through the key elements in the textbook on Latitude, Altitude, Distance from sea and Cloud cover.
  • Tendency for more rainfall around areas near sea. Coupled with relief factors, distance from sea can affect temperature.
  • Talk about polar regions where there are periods of no sunlight
    30days of night trailer
  • Show random mountain climbing videos up snowcapped mountains.
    http://www.youtube.com/watch?v=Du54zAXM3Eg
    Watch clip on climbing everest
    Think about the presence of snow and the implications on temperature
  • Link to video: http://www.youtube.com/watch?v=nNzDXXUiqRs
  • East Coast vs AMK…why is it more desirable to live in East Coast?

    http://www.propertyguru.com.sg/listing/hdb-for-sale-180-ang-mo-kio-avenue-5-14142377
    AMK
    http://www.propertyguru.com.sg/listing/hdb-for-sale-27-marine-crescent-13952694
    Marine Terrace
  • Write on A4/A3 paper, pin on exterior / interior classroom walls for reference and peer learning.
  • Link to http://www.youtube.com/watch?v=E8AvfXar9zs&list=PLDA6466A452C9053B
    Link to http://www.youtube.com/watch?v=NiCSk1zxMEs&list=PLDA6466A452C9053B
  • Link to http://www.youtube.com/watch?v=bHHHRSBvo9o&list=PLDA6466A452C9053B
  • Link to
  • Link to http://www.youtube.com/watch?v=bHHHRSBvo9o&list=PLDA6466A452C9053B
  • ×