2 Definition Temperature is the degree of heat or cold in the atmosphere It is measured in ºC or ºF
3 Warming of air Air is warmed by means of: Convection: The process through which hot air, being lighter than cold air, rises as a convection currentConduction: The process through which the air receives heat from the ground it is in contact withRadiation: The process through which the heat energy from the ground is sent back to space. This form of heat energy can travel in a vacuum.
5 Factors influencing temp LatitudeAltitudeDistance from the seaOcean currentsAspectHumidity and cloud coverLand surface
6 LatitudePlaces near the Equator are hotter than places near the poles due to the angle at which sun’s ra strike the EarthAmount of heat received by Earth’s surfaces decreases with latitude due to the decreasing angle of incidence Angle at which sun’s ray hits earth) of the sun’s ray
8 Latitude (cont)In reality, Earth’s axis is tilted at an angle of 23.5º from the verticalFrom June to Aug, there is a higher intensity of the sun’s ray in the northern hemisphereThe higher latitudes in the northern hemisphere therefore experience higher temperature in summer while the higher latitudes in the southern hemisphere experience low temp in winter.
10 AltitudeTemperature falls by 6.4ºC for every 1000m increase in height.This fall in temperature is called the normal lapse rate.Air is warmed by the heat radiated from the ground due to conduction and convection. It is much warmer as there is larger landMost of Earth's surface gases is also concentrated at the Earth’s surface.
12 Altitude(cont)Temp sometimes rise with altitude in the troposphere due to:Rapid outgoing terrestrial radiation on a cloudless night.Cold air rolling down slope displacing the Warmer airWarm air rises over cold air at a warm frontCold air undercutting warm air at a cold front
13 Distance from the seaSea heats up and loses heat more slowly than landCoastal area temperature is influenced.In temperate latitudes, coastal areas have a smaller temperature range between summer and winter(not as hot in summer and not as cold in winter)Inland areas far from the sea are not affected by the ocean thus have larger annual temp range.
14 Ocean CurrentsChange in temperature is due to ocean currents in the areaOcean current are set in motion by prevailing winds blowing over the surface2 types of ocean currents:Warm – Originates from equatorCold – Originates from higher latitudes
16 AspectsRefers to the direction of the slope of the land relative to the sunMore obvious in temperate regions rather than tropical regionsIn northern hemisphere, south facing slope have higher temp than north facing slopeFaces the sun.
17 Humidity and cloud cover Humidity is the state of the atmosphere with respect o its amount of water vapourThe higher the humidity, the more clouds there will be as clouds are formed by condensation of water vapour.Thick cloud cover prevents solar radiation from entering in the day and outgoing terrestrial radiation escaping in the night.Therefore, equatorial areas which have high humidity and thick cloud cover has low diurnal temp range.
18 Type of land surfaceAn area with vegetation is much cooler than an area of concrete.Vegetation reduce the incoming radiation and prevents absorption of heat into the ground.Concrete surfaces absorbs h eat quickly in the day and releases heat lowly at night.“Urban Heat islands”Cause? Effects? (group work)
19 Instruments used to measure temperature Daily Maximum and minimum temperatureDaily maximum temperature: the highest temperature reading for the dayDaily minimum temperature: the lowest temperature reading for the day
20 Maximum and Minimum Thermometer Maximum temperature is measured by the maximum thermometerIt consists of a glass tube containing mercury and a metal indexWhen temperature rises, the mercury expands and pushes the metal index upwardsWhen temperature falls and the mercury contracts, the metal index stays in placeThe minimum thermometer works in the same way, but contains alcohol instead of mercury
22 Temperature Calculations Diurnal Temperature range:Max temp – Min tempAverage Daily Temp(Max Temp + Min Temp) / 2Total of hourly Temp / 24Mean Monthly TempTotal of ave daily temp / total no. of daysMean Annual TempTotal of 12 mean mthly temp / 12