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O-Level Weather and Climate (Topic 3.1)
the variables of weather and why temperature, rainfall and wind vary
What the syllabus expects
- Weather is the condition of the atmosphere at a particular time and place, described by variables such as wind direction, wind speed, precipitation, cloud cover and air temperature.
Scope: The meaning of weather and climate - Climate is the average atmospheric state across a defined period, with types including cool temperate climate, tropical monsoon climate and tropical equatorial climate.
Scope: The meaning of weather and climate - Climatic hazards arise from shifts in climate and from extreme weather such as wildfires, cyclones, floods, droughts and heat waves, and weigh heavily on natural and human systems.
Scope: The meaning of weather and climate - Earth's spin on its axis produces temperature swings through the day, while its journey around the sun produces temperature swings through the year.
Scope: Why air temperature differs across Earth's surface - Globally, lower solar angles at higher latitudes give lower temperatures, and locally, lower air pressure at higher altitudes gives lower temperatures.
Scope: Why air temperature differs across Earth's surface - Surface types such as snow cover, vegetation and exposed soil shape site-specific temperatures, as do the maritime effect on coasts and the continental effect inland.
Scope: Why air temperature differs across Earth's surface - The water cycle moves water between the atmosphere and Earth's surface via evapotranspiration, condensation and precipitation, and at varying rates as infiltration, surface runoff and groundwater flow.
Scope: Why precipitation differs across Earth's surface - Relative humidity governs condensation, which depends on the amount of water vapour present and happens once that vapour exceeds what the atmosphere can hold at a given temperature.
Scope: Why precipitation differs across Earth's surface - Clouds form from condensation nuclei and the merging of water droplets in the atmosphere, yielding precipitation such as convectional and relief rainfall.
Scope: Why precipitation differs across Earth's surface - An uneven spread of air temperature creates an uneven pressure gradient, which sets air moving horizontally and fixes the wind's direction.
Scope: Why wind direction and speed differ across Earth's surface - Wind speed depends on how strong the pressure gradient is between two places and on the friction created by Earth's topography.
Scope: Why wind direction and speed differ across Earth's surface - Land and sea breezes are local winds, while the Northeast and Southwest monsoons are regional winds shaped by the Coriolis force.
Scope: Why wind direction and speed differ across Earth's surface
How it's examined
About 4% of the past-paper style questions in Rae's bank for this subject sit in this topic.
Worked examples
Example 1 (4 marks)
Account for how the regional winds that affect Singapore between October and February are formed.
Show the worked answer
Between October and February the overhead sun is in the Southern Hemisphere, so the large Asian landmass cools rapidly and forms a zone of high pressure (over Siberia/central Asia). The seas and the landmasses to the south stay warmer, creating relatively lower pressure there. Winds blow from the high-pressure area towards the low-pressure area, moving out of Asia towards the south. Deflection by the Coriolis effect gives them a north-easterly direction as they cross Singapore, forming the Northeast Monsoon winds, which pick up moisture as they travel over the sea.
More O-Level Geography topics
Thinking Geographically (Topic 1.1) · Sustainable Development (Topic 1.2) · Geographical Methods (Topic 1.3) · Tourism Activity (Topic 2.1) · Tourism Development (Topic 2.2) · Sustainable Tourism Development (Topic 2.3) · all of O-Level Geography