Atmosphere, Weather and Climate

Structure of Earth’s Atmosphere Atmosphere

A layer of air which surrounds the Earth It is held in place by the pull of Earth’s gravitional forces Earth’s gravity is strongest nearer to the surface, therefore, most

of the atmosphere is found near the surface. Consists mostly of:

Nitrogen Oxygen Water vapour Dust particles

The Atmosphere The Atmosphere (cont’d)(cont’d)

Other gases (carbon dioxide, water vapour)

1%

Oxygen 21%

Nitrogen 78%

Upper part of the atmosphere contains little atmospheric water vapour and other gases and experiences no changes in weather.

Troposphere contains most atmospheric water vapour, other gases and dust and experiences weather changes

Importance of the AtmosphereImportance of the Atmosphere

Helps sustain life Protects the Earth

Weather and Weather and

ClimateClimate

WeatherThe Sun’s rays

heat up theEarth’s land and sea surfaces

Heat reflected from these surfaces warm up the air above

Hot air rises and causes condition of the atmosphere to change

Weather VS Climate

Weather and Climate Weather and Climate (cont’d)(cont’d)

WeatherWhen this happens, we experience a change

in weatherMeteorologists define ‘weather’ as the condition

of the atmosphere at a particular place over a short period of time

Weather and Climate Weather and Climate (cont’d)(cont’d)

ClimateWeather pattern of a place over a long period of time,

usually 30 years The basic elements of weather and climate:

SunshineTemperatureHumidityCloudsRainfallAir pressureWind

How Weather and Climate Affect How Weather and Climate Affect PeoplePeople

Weather affects our daily life Climate affects how people live generally

Where people choose to liveTypes of houses people live in

Climate affects food and water supply

Measuring Temperature

Daily Maximum and MinimumDaily Maximum and Minimum

TemperaturesTemperatures

Daily maximum temperature: the highest temperature reading for the day

Daily minimum temperature: the lowest temperature reading for the day

Maximum and Minimum ThermometersMaximum and Minimum Thermometers

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

Where to Place ThermometersWhere to Place Thermometers

Instruments used to measure temperature are usually placed in a Stevenson ScreenA raised white wooden box with louvres

Shelters the instruments from the direct heat of the SunAllows air to flow freely through itAvoids heat radiating from the ground

Mean Daily TemperatureMean Daily Temperature

The average temperature of a place on any one day Daily recording of this temperature reveals a

pattern which provides a more accurate picture of the climate of the place

Mean Daily Temperature Mean Daily Temperature (cont’d)(cont’d)

Formula for calculating mean daily temperature

Mean

daily

temperature

Daily maximum temperature

+

Daily minimum temperature

2

=

Mean Daily Temperature Mean Daily Temperature (cont’d)(cont’d)

Mean daily temperature for SingaporeDaily maximum temperature is often 32 degrees

CelsiusDaily minimum temperature is often 25 degrees CelsiusMean daily temperature =

=

(32 + 25)OC

2

28.5OC

Diurnal Temperature RangeDiurnal Temperature Range Shows how extreme temperatures can get within a

day Used for describing the climate of a place Formula:

Diurnal

Temperature

range

=

Daily

maximum

temperature

Daily

minimum

temperature-

Diurnal Temperature Range Diurnal Temperature Range (cont’d)(cont’d)

Diurnal temperature range for Singapore= (32 - 25)OC

= 7OC