Atmosphere, Weather and Climate

Structure of Earth’s 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

Other gases (carbon dioxide, water vapour) 1% The Atmosphere (cont’d) Other gases (carbon dioxide, water vapour) 1% Nitrogen 78% Oxygen 21%

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 Atmosphere Helps sustain life Protects the Earth

Weather and Climate Weather The Sun’s rays heat up the Earth’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 (cont’d) When this happens, we experience a change in weather Meteorologists define ‘weather’ as the condition of the atmosphere at a particular place over a short period of time

Weather and Climate (cont’d) Weather pattern of a place over a long period of time, usually 30 years The basic elements of weather and climate: Sunshine Temperature Humidity Clouds Rainfall Air pressure Wind

How Weather and Climate Affect People Weather affects our daily life Climate affects how people live generally Where people choose to live Types of houses people live in Climate affects food and water supply

Measuring Temperature

Daily Maximum and Minimum Temperatures Daily maximum temperature: the highest temperature reading for the day Daily minimum temperature: the lowest temperature reading for the day

Maximum 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 Thermometers Instruments used to measure temperature are usually placed in a Stevenson Screen A raised white wooden box with louvres Shelters the instruments from the direct heat of the Sun Allows air to flow freely through it Avoids heat radiating from the ground

Mean 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 (cont’d) Formula for calculating mean daily temperature Daily maximum temperature + Daily minimum temperature Mean daily temperature = 2

Mean Daily Temperature (cont’d) Mean daily temperature for Singapore Daily maximum temperature is often 32 degrees Celsius Daily minimum temperature is often 25 degrees Celsius Mean daily temperature = (32 + 25)OC 2 28.5OC =

Diurnal 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 (cont’d) Diurnal temperature range for Singapore = (32 - 25)OC = 7OC