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Temperature and Its Variation. Earth’s Rotation Remember we live on a rotating sphere Direction of rotation: –From above North Pole, counterclockwise.

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Presentation on theme: "Temperature and Its Variation. Earth’s Rotation Remember we live on a rotating sphere Direction of rotation: –From above North Pole, counterclockwise."— Presentation transcript:

1 Temperature and Its Variation

2 Earth’s Rotation Remember we live on a rotating sphere Direction of rotation: –From above North Pole, counterclockwise –From a distance, with North Pole at top, left to right Remember we live on a rotating sphere Direction of rotation: –From above North Pole, counterclockwise –From a distance, with North Pole at top, left to right

3 Effects of Earth’s Rotation 3 main effects: –Axis and equator basis of geographic grid –A day is a convenient measure of time passing –Diurnal, or daily, rhythm in daylight, air temp, etc. Surface processes all respond to diurnal rhythm Coriolis force due to Earth’s rotation –How fast are you moving at the Equator? –At the Poles? 3 main effects: –Axis and equator basis of geographic grid –A day is a convenient measure of time passing –Diurnal, or daily, rhythm in daylight, air temp, etc. Surface processes all respond to diurnal rhythm Coriolis force due to Earth’s rotation –How fast are you moving at the Equator? –At the Poles?

4 Earth’s Revolution around Sun days / orbit → Feb 29 th every 4 th year Counterclockwise motion from above days / orbit → Feb 29 th every 4 th year Counterclockwise motion from above Elliptical orbit: There is a 6% difference in insolation between Perihelion and Aphelion. Perihelion – Closest to Sun – Jan. 3 rd Aphelion – Farthest from Sun – July 4 th

5 World Latitude Zones Terms used for latitude zones Generally greater seasonal change with greater distance from Equator Terms used for latitude zones Generally greater seasonal change with greater distance from Equator

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10 Solar Heating of Land & Water Surface layer of large body of water heats & cools more slowly than land This difference shows up in temp patterns –e.g. diurnal temp pattern, maritime vs. continental Surface layer of large body of water heats & cools more slowly than land This difference shows up in temp patterns –e.g. diurnal temp pattern, maritime vs. continental San Francisco (Maritime) Yuma (Continental)

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13 Thermal Properties of Water 4 factors make water heat & cool slower than land 1. Sun penetrates water 2. Heat capacity of water greater 3. Water mixes 4. More evaporation over water

14 5 Factors Influencing Local Temps Latitude – less insolation at higher latitudes Surface type – urban land absorbs more heat Coastal vs. Interior – less temp range at coast Elevation – temps decrease with altitude –Greater annual temp range at high latitudes Atmospheric & oceanic circulation- temp can vary greatly based on where air & sea water are coming from Latitude – less insolation at higher latitudes Surface type – urban land absorbs more heat Coastal vs. Interior – less temp range at coast Elevation – temps decrease with altitude –Greater annual temp range at high latitudes Atmospheric & oceanic circulation- temp can vary greatly based on where air & sea water are coming from

15 Urban Heat Island Evapotranspiration helps keep rural areas cool –Urban asphalt & concrete has little evapotranspiration Building & paving materials absorb more heat than natural surfaces Automobiles, air conditioning & other machines make city warmer than surroundings Evapotranspiration helps keep rural areas cool –Urban asphalt & concrete has little evapotranspiration Building & paving materials absorb more heat than natural surfaces Automobiles, air conditioning & other machines make city warmer than surroundings

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19 Daily Cycle of Radiation & Air Temp Shortwave radiation from Sun greater than longwave radiation during daylight hours. Energy surplus in daylight Deficit in darkness Temp usually highest in mid- afternoon, lowest just after sunrise

20 Maritime vs. Continental Daily range of temp less at maritime location North Head, WA much less range than El Paso, TX throughout the year Daily range of temp less at maritime location North Head, WA much less range than El Paso, TX throughout the year

21 Annual Cycle of Air Temperature Annual temperature range = max temp month – min temp month 2 most important factors: –Annual insolation (latitude) –Maritime or continental effect Like daily temp cycle, maritime climates have less annual temp range than continental Annual temperature range = max temp month – min temp month 2 most important factors: –Annual insolation (latitude) –Maritime or continental effect Like daily temp cycle, maritime climates have less annual temp range than continental

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24 Annual Cycle of Air Temperature Winnipeg & Scilly Is. have identical insolation curves Winnipeg much colder fall, winter, spring due to extreme continental location Scilly Is. Reach max & min temps later Due to influence of water Winnipeg & Scilly Is. have identical insolation curves Winnipeg much colder fall, winter, spring due to extreme continental location Scilly Is. Reach max & min temps later Due to influence of water

25 World Temperature Patterns Isotherm – line on map connecting all points with same temperature January Coldest in Siberia, northern Canada & Greenland Warmest in southern Africa and interior Australia Oceans warmer than land in northern hemisphere

26 World Temperature Patterns Maritime influence warms in winter, cools in summer July Northern hemisphere continents have warmed dramatically since January Aside from Antarctica, southern hemisphere not very cold in winter Maritime influence

27 Annual Temperature Range = warmest month mean temp – coldest month mean temp Greatest temp ranges in Siberia & NW Canada Continental locations Smallest temp ranges in Equatorial oceans Maritime influence

28 Wind-Chill Index “Feel” of temperature – based on: –Actual temperature –Windspeed – higher means colder “Feel” of temperature – based on: –Actual temperature –Windspeed – higher means colder

29 Heat Index “Feel” of temperature on hot days, based on: –Actual temperature –Relative Humidity “Feel” of temperature on hot days, based on: –Actual temperature –Relative Humidity

30 Chapter Summary Earth’s rotation and orbit Air Temperature Daily cycle of air temperature Annual cycle of air temperature Measurement of air temperature Earth’s rotation and orbit Air Temperature Daily cycle of air temperature Annual cycle of air temperature Measurement of air temperature


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