Higher ground is generally cooler. Vegetation changes surface heating, while the sea reduces temperature extremes near the coast.
Temperature generally falls with height in the troposphere, the lowest layer of the atmosphere. Air pressure falls because there is less air above. Rising air expands in this lower pressure and cools. The lower atmosphere also receives much of its heat from the ground. A lapse rate describes temperature change with height, but it is an approximation: local temperature inversions can reverse the pattern.
Albedo is the share of incoming sunlight a surface reflects. Snow has a high albedo and reflects much of the sunlight. Darker surfaces often absorb more energy. Keep surface and air temperatures separate: a hot road surface does not have the same temperature as the air above it.
Vegetation cools its surroundings through shade and evapotranspiration, which uses energy to turn water into vapour. Wet soil also allows more evaporative cooling than dry soil. Buildings and roads store heat and release it later. Less vegetation and heat from human activity can make urban air warmer. The effect varies with moisture, material and time of day.
The sea reduces nearby temperature extremes. Water has a higher heat capacity than land and mixes heat through its depth, so it warms and cools more slowly. This maritime effect brings cooler summers and milder winters near the coast. Inland places often have a larger annual range: the continental effect. Compare places at similar latitudes and heights to isolate the sea's influence.
Step by step
Height
Rising air expands as pressure falls, then cools.
Surface cover
Shade and evaporation reduce heating; dark surfaces often absorb more sunlight.
Distance from the sea
Slow heating and cooling of water reduces coastal temperature extremes.
Worked example: An illustrative coastal comparison
Two sites at similar latitude and height have annual temperature ranges of 12 and 26 degrees C. If the first is coastal and the second far inland, slower heating and cooling of the nearby sea can explain the smaller coastal range. These are teaching values, not observations from named stations.
Watch out for this
A mountain is cold because it is farther from the equator.
Altitude is height above sea level; latitude is angular position north or south of the equator. A mountain can be high while remaining close to the equator.
Check your understanding
Why might a shaded, well-watered park have cooler daytime air than nearby exposed paving?
- The park must have a lower latitude.
- Shade reduces heating and evapotranspiration uses energy.
- All green surfaces reflect every incoming ray.