Weather, Climate and Atmosphere
Weather, Climate and Atmosphere
Distinguish weather (short-term atmospheric conditions) from climate (long-term averages and patterns). Know the atmosphere's layers - troposphere (weather), stratosphere (ozone), mesosphere, thermosphere - and the gases: nitrogen and oxygen dominate, with carbon dioxide, water vapour and ozone in small but vital amounts.
Understand how the Earth is heated: insolation is strongest near the equator, giving low angles of incidence and high angles near the poles; this creates the pressure belts (equatorial low, subtropical highs, subpolar lows, polar highs) and the global wind belts (trade winds, westerlies, polar easterlies), modified by the Coriolis effect. Learn air masses and fronts (cold, warm, occluded), depression formation, and convectional, relief and frontal rainfall. Climate controls include latitude, altitude, distance from the sea, ocean currents, prevailing winds and relief.
Traps: saying the equator is hottest because it is closest to the Sun; confusing weather with climate; reversing trade-wind directions; forgetting that warm ocean currents raise coastal temperatures; and muddling relief rainfall (air forced up over hills) with convectional rainfall (surface heating).
Rule of thumb: rising air gives low pressure and rain; sinking air gives high pressure and dry conditions. Link every rainfall type to how air is forced to rise.
Worked example: A town on a tropical coast records heavy afternoon rain in summer. Reasoning: intense surface heating causes air to rise rapidly (convection), cool, condense and form cumulonimbus clouds - convectional rainfall, typical of equatorial and tropical climates.