2. Backward Forward Home Exit III. How do temperatures change over time and over place? 1. What are some common records of temperature? Mean daily temperatureMean daily temperature : the average of temperatures during a day Diurnal/daily range of temperatureDiurnal/daily range of temperature : the difference between the maximum and minimum temperatures recorded during a day Temperature °C or °F Temperature is a measurement of degree of hotness or coldness. It is measured in °C or °F. Some common temperature records include:

3. Backward Forward Home Exit Mean monthly temperatureMean monthly temperature : the average of mean daily temperatures during a month Annual range of temperatureAnnual range of temperature : the difference between the highest and lowest mean monthly temperatures during a year Mean annual temperatureMean annual temperature : the average of mean monthly temperatures over a year

4. Backward Forward Home Exit 2. How do the daily and annual temperatures change with the energy budget? It takes time for the ground to absorb solar radiation, and then to emit long-wave radiation into the atmosphere Therefore, the maximum temperature is usually recorded in the afternoon It also takes time for cooling to occur and therefore the minimum temperature is recorded at some time around sunrise

5. Backward Forward Home Exit For the northern hemisphere, the minimum and maximum mean monthly temperatures are usually recorded in January and July respectively (instead of the time around the solstices) Therefore, we generally use January and July periods to represent typical atmospheric conditions in winter and summer seasons respectively

6. Backward Forward Home Exit 3. What are the factors affecting temperature? Continentality a. Continentality Due to the different properties of land and water Land heats up more rapidly than water Land heats up more rapidly than water Therefore, higher temperatures are recorded above land than over the sea in summer Since water has a large capacity to store heat, it cools down more slowly than land. As a result, lower temperatures are observed above land than over the sea in winter Since water has a large capacity to store heat, it cools down more slowly than land. As a result, lower temperatures are observed above land than over the sea in winter

7. Backward Forward Home Exit A hotter summer and a colder winter together result in a greater annual range of temperature over landA hotter summer and a colder winter together result in a greater annual range of temperature over land An increased range of annual temperatures with increasing distance from the seaAn increased range of annual temperatures with increasing distance from the sea

8. Backward Forward Home Exit Shanghai is a coastal city Coastal locations often enjoy milder temperatures while inland locations often exhibit more extreme temperatures

9. Backward Forward Home Exit b. Ocean currents Ocean currents are movements of surface water in the oceans

10. Backward Forward Home Exit Warm currents move poleward and cold currents move equatorward

11. Backward Forward Home Exit Halifax, Canada is affected by cold current Warm currents raise the temperature of coastal areas they pass by while cold currents reduce temperatures

12. Backward Forward Home Exit The famous warm current North Atlantic Drift keeps the North Sea in Western Europe free from freezing, and contributes to the fishing industries

13. Backward Forward Home Exit If you cannot see the movie, click here to download the Macromedia Shockwave Player click here

14. Backward Forward Home Exit c. Altitude At the lowest part of the atmosphere, known as the troposphere, air temperature generally decreases with increasing altitude

15. Backward Forward Home Exit At higher altitudes, the density of air is lower. As a result, there is less dust, water vapour and carbon dioxide to absorb heatAt higher altitudes, the density of air is lower. As a result, there is less dust, water vapour and carbon dioxide to absorb heat Higher places are farther away from most terrestrial radiationHigher places are farther away from most terrestrial radiation

16. Backward Forward Home Exit The rate of temperature falls with increasing altitude is known as the lapse rate The environmental lapse rate is around 6.5°C per 1 km increase in altitude

17. Backward Forward Home Exit IV. How do global patterns of temperature change during the year? 1. What are the major factors affecting global patterns of temperature? Isotherms: lines joining places with equal temperatures useful for showing spatial variations in temperature Isotherm maps: showing global patterns of air temperature reflections of the combined effects of major factors affecting temperature

18. Backward Forward Home Exit a. Temperature patterns in January Northern hemisphere: winter season winter season temperatures are generally lower temperatures are generally lower Southern hemisphere: continents are heated intensely in the tropics continents are heated intensely in the tropics isotherms run parallel to latitudes over ocean surfaces isotherms run parallel to latitudes over ocean surfaces

19. Backward Forward Home Exit b. Temperature patterns in July Northern hemisphere: Isotherms bend northward over continents because they are warmer than the seaIsotherms bend northward over continents because they are warmer than the sea Some exceptions include coastal areas of NE Asia and the west coast of North AmericaSome exceptions include coastal areas of NE Asia and the west coast of North America Southern hemisphere: Isotherms are almost parallel to latitudesIsotherms are almost parallel to latitudes A uniform poleward decrease of temperature persistsA uniform poleward decrease of temperature persists Winters are not very cold because most of it is oceanWinters are not very cold because most of it is ocean