elements of weather & climate temperature. definition temperature is the degree of heat or cold...
Post on 20-Dec-2015
218 views
TRANSCRIPT
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 current
Conduction: The process through which the air receives heat from the ground it is in contact with
Radiation: 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.
Factors influencing temp
Latitude Altitude Distance from the sea Ocean currents Aspect Humidity and cloud cover Land surface
Latitude
Places near the Equator are hotter than places near the poles due to the angle at which sun’s ra strike the Earth
Amount 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
Latitude (cont)
In reality, Earth’s axis is tilted at an angle of 23.5º from the vertical
From June to Aug, there is a higher intensity of the sun’s ray in the northern hemisphere
The 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.
Altitude
Temperature 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 land
Most of Earth's surface gases is also concentrated at the Earth’s surface.
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 air Warm air rises over cold air at a warm front Cold air undercutting warm air at a cold
front
Distance from the sea
Sea heats up and loses heat more slowly than land
Coastal 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.
Ocean Currents
Change in temperature is due to ocean currents in the area
Ocean current are set in motion by prevailing winds blowing over the surface
2 types of ocean currents: Warm – Originates from equator Cold – Originates from higher latitudes
Aspects
Refers to the direction of the slope of the land relative to the sun
More obvious in temperate regions rather than tropical regions
In northern hemisphere, south facing slope have higher temp than north facing slope
Faces the sun.
Humidity and cloud cover
Humidity is the state of the atmosphere with respect o its amount of water vapour
The 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.
Type of land surface
An 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)
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
Maximum and Minimum Thermometer Maximum temperature is measured by the maximum
thermometer It consists of a glass tube containing mercury and
a metal index When temperature rises, the mercury expands and pushes
the metal index upwards When temperature falls and the mercury contracts,
the metal index stays in place
The minimum thermometer works in the same way, but contains alcohol instead of mercury