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

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III. How do temperatures change III. How do temperatures change over time and over place?over time and over place?

III. How do temperatures change III. How do temperatures change over time and over place?over time and over place?

1. What are some common records of 1. What are some common records of temperature?temperature?

1. What are some common records of 1. What are some common records of temperature?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

TemperatureTemperature is a measurement of degree of hotness

or coldness. It is measured in °C°C oror °F°F. Some common temperature records include:


• 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


2. How do the daily and annual temperatures 2. How do the daily and annual temperatures change with the energy budget?change with the energy budget?

2. How do the daily and annual temperatures 2. How do the daily and annual temperatures change with the energy budget?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


• 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


3. What are the factors affecting temperature?3. What are the factors affecting temperature?3. What are the factors affecting temperature?3. What are the factors affecting temperature?a. ContinentalityContinentality

Due to the different properties of land and water

• Land heats up more rapidly than waterLand heats up more rapidly than water• Therefore, higher temperatures are recorded above

land than over the sea in summer

• Since Since water has a large capacity to store heatwater has a large capacity to store heat, it , it

cools down more slowly than land. As a result, lower cools down more slowly than land. As a result, lower

temperatures are observed above land than over the temperatures are observed above land than over the

sea in wintersea in winter


• A A hotter summerhotter summer and and

a a colder wintercolder winter

together result in a together result in a

greater annual range greater annual range

of temperature over of temperature over

landland

• An An increased range of increased range of

annual temperatures annual temperatures

with increasing with increasing

distance from the seadistance from the sea


Shanghai is a coastal city

Coastal locations often enjoy Coastal locations often enjoy milder temperatures while milder temperatures while inland locations often exhibit inland locations often exhibit more extreme temperaturesmore extreme temperatures


b. Ocean currentsb. Ocean currentsOcean currents are movements Ocean currents are movements of surface water in the oceansof surface water in the oceans


Warm currents move Warm currents move polewardpoleward and and cold cucold currents move equatorrrents move equatorwardward


Halifax, Canada is affected by cold current

Warm currentsWarm currents raise the temperature raise the temperature of coastal areas they pass by while of coastal areas they pass by while

cold currentscold currents reduce temperatures reduce temperatures

Warm currentsWarm currents raise the temperature raise the temperature of coastal areas they pass by while of coastal areas they pass by while

cold currentscold currents reduce temperatures reduce temperatures


The famous warm current North Atlantic Drift keeps the North Sea in Western Europe free from freezing, and contributes to the fishing industries


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c. Altitudec. AltitudeAt the lowest part of the atmosphere, known as the At the lowest part of the atmosphere, known as the

troposphere, troposphere, air temperatureair temperature generally generally decreases decreases with increasing altitudewith increasing altitude


• At higher altitudes, the At higher altitudes, the

density of air is lowerdensity of air is lower. .

As a result, there is less As a result, there is less

dust, water vapour and dust, water vapour and

carbon dioxide to absorb carbon dioxide to absorb

heatheat

•Higher places are Higher places are

farther away from most farther away from most

terrestrial radiationterrestrial radiation


• 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


IV. How do global patterns of temperature IV. How do global patterns of temperature change during the year?change during the year?

IV. How do global patterns of temperature IV. How do global patterns of temperature change during the year?change during the year?

1. What are the major factors affecting global 1. What are the major factors affecting global patterns of temperature?patterns of temperature?

1. What are the major factors affecting global 1. What are the major factors affecting global patterns of temperature?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


a. Temperature patterns in Januarya. Temperature patterns in January

Northern hemisphere:Northern hemisphere:

• winter seasonwinter season

• temperatures are generally lowertemperatures are generally lower

Southern hemisphere:Southern hemisphere:

• continents are heated intensely in the tropicscontinents are heated intensely in the tropics

• isotherms run parallel to latitudes over ocean surfacesisotherms run parallel to latitudes over ocean surfaces


b.b. Temperature patterns in JulyTemperature patterns in July

Northern hemisphere:Northern hemisphere:• Isotherms bend northward over continents because Isotherms bend northward over continents because

they are warmer than the seathey are warmer than the sea• Some Some exceptionsexceptions include include coastal areas of NE Asiacoastal areas of NE Asia and and

the west coast of North Americathe west coast of North America

Southern hemisphere: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

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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