temperature weather and climate. temperature refers to the degree of hotness or coldness of the air...
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Temperature
Temperature refers to the degree of hotness or coldness of the air
It varies throughout the day in a place
The temperature rises and falls as the Earth rotates from west to east and it rises during the day and falls at night
It also varies from place to place
Temperature gets cooler as we go to higher grounds
Places nearer the Equator are warmer throughout the year than places farther away from it
Elements of Weather: Temperature
Singapore What is the reason for
Singapore’s hot climate?
Elements of Weather: Temperature
Factors Affecting Temperature
1. Latitude
• Due to angle of incidence, the sun’s ray travels a shorter distance through the atmosphere and the solar radiation is concentrated on a smaller area
• These places experience uniform temperatures annually due to the tilt of the earth on its axis and cause these places to face the sun and receive the same radiation all year round.
Places at lower latitudes are always hotter than those at higher latitudes
Factors Affecting Temperature
2. Altitude
• Temperature falls as altitude increases at a rate of 6.5°C/1000m (known as the Normal lapse rate)
• Air is less dense at higher altitudes -> absorb less long wave radiation -> lower temperatures
Measuring Temperature
Air temperature is measured with a thermometer
The scale is in degree Celsius (OC)
Daily maximum temperature refers to the highest temperature reading for the day
Daily minimum temperature refers to the lowest temperature reading for the day
Glass tube
Mercury or alcohol
Measuring Temperature
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
Measuring Temperature
The minimum thermometer works in the same way to measure the lowest temperature reading, but contains alcohol instead of mercury
The maximum and minimum thermometer, which is also called the U-shaped thermometer, can measure both maximum and minimum temperatures
Six’s Thermometer
Six’s Thermometer/U-shaped thermometer
left bulb right bulb
metal index
vacuum
alcohol
mercury
right bulb
Six’s Thermometer• When temp increases,
both alcohol and mercury expand
alcohol in the left limb forces the mercury towards the right limb
the mercury pushes the index up in the right limb
part of the alcohol in the right limb vaporises and moves into the vacuum
end of the index closest to the mercury gives the maximum temperature
Six’s Thermometer
• When temp decreases,
both alcohol and mercury contract
alcohol vapour in the right bulb liquifies so that the mercury now flows in the opposite direction and pushes the up the metal index in the left limb
end of the index closest to the mercury gives the minimum temperature
• Diurnal temperature range
• Average temperature range
• Mean monthly temperature
• Annual range of temperature
• Mean annual temperature
Calculating Temperatures
• The mean daily temperature is the average temperature of a place on any one day
FormulaMean daily
temperature =
Daily maximum Daily minimum temperature + temperature
2
• The daily temperature range is the difference between the maximum and minimum temperatures recorded in a day
Formula Daily temperature range =
Daily maximum Daily minimum temperature - temperature
Calculating Temperatures
Calculating Temperatures
• The mean monthly temperature is the average temperature of a place in a month
FormulaMean monthly
temperature =
Sum of mean daily temperatures for the month
Number of days in the month
• The mean annual temperature is the average temperature in a place within a year
FormulaMean annual
temperature =Sum of mean monthly temperatures in the year
2
Calculating Temperatures
• The annual temperature range is the difference between the maximum and minimum mean monthly temperatures recorded in a year
Formula Annual temperature range =
Maximum Minimum mean monthly - mean monthly temperature temperature
Elements of Weather: Temperature
Isotherms: lines joining places of equal temperature
Elements of Weather: Temperature
Line graph:
Stevenson Screen
Instruments used to measure temperature are usually placed in a Stevenson Screen
Maximum and minimum thermometers or six’s thermometer and a wet and dry bulb thermometer are kept in the SS.
Barometer can also be kept in SS
Stevenson ScreenIt is made of wood
✓wood is a poor conductor of heat
It is painted white
✓white paint reflects light so that the box does not heat up excessively
Its is a raised 1.2 metres above ground
✓to minimise the effect heat radiating from the ground
Stevenson Screen
The sides and doors have louvres
✓to allow free air movement in and out of the boxdirect heat of the Sun
It has a double-layered roof with intervening air space
✓to reduce excessive heating inside the box as air is a good insulator
✓Where should a stevenson screen be sited?