Weather and Climate: How Altitude Affects Temperature

Temperature decreases with altitude, which is the height of a place in relation to the sea level.

Temperature generally decreases by 6.5°C for every 1000 metres increase in altitude. (note in the diagram below, the temperature at the base level 0m starts at 19.5°C, decreases to 0°C at 3000m and reaches  -13°C at 5000m).

Altitude affects temperature in two ways
1) Distance from Earth's Surface
2) Density of Air

Distance from Earth's Surface
Temperature decreases with altitude because the atmosphere is mostly heated up by the earth's surface.

When the sun's solar energy enters the atmosphere, it reaches the earth's surface in the form of shortwave radiation. About 45% of the total solar energy entering is directly absorbed by the earth's surface, heating it up. The warm surface of the earth then emits heat in the form of longwave radiation.

Air that is nearer to the earth is nearer to the source of heat. Thus it absorbs more heat than air at the higher altitudes. Therefore with increasing altitude, temperature will fall.

Density of Air
Due to the force of gravity, more air molecules are nearer to the surface of the earth (refer to diagram below). As a result, air is denser at a lower altitude (nearer to earth's surface) because of gravity.

Each air molecule has the ability to trap heat. Thus, where there are more air molecules, more heat will be trapped. Denser air in the lower altitude has a greater ability to absorb heat than less dense air in the higher altitude.

Density of Air with Increasing Altitude

How Density of Air Affects Temperature (Altitude)

High Altitude --> Air less dense, unable to absorb more heat --> Lower Temperature

Low Altitude --> Air more dense, able to absorb more heat --> Higher Temperature

Click on the link below to answer the quiz to test your understanding :)

https://docs.google.com/forms/d/1l8CGVawaSfC8RDJtgKN2BxL2MDH_PqlY6s5QQ8NiMuI/prefill?pref=2&pli=1

Click on the image below to check if you managed to get the correct answers to the quiz :)

Weather & Climate: How Latitude Affects Temperature

Temperature varies across the earth for various reasons. Some places are colder while others are warmer. Factors that cause this variations in temperature across the globe include;

1) Latitude
2) Altitude
3) Distance from the Sea
4) Cloud Cover

What is Latitude?

Latitude refers to the distance of any point on the earth, measured north or south from the Equator.

It is an imaginary horizontal line running across from east to west around the earth, measured in degrees.

The Equator is at a latitude of 0°, while the North Pole is at 90°N and South Pole 90°S.

Singapore is located at latitude 1°22'N.

Latitude is the most important factor affecting temperature!!!

• Temperature differs between places of lower latitudes and higher latitudes because the sun's rays strike at different parts of the world at different angles.
• Angle of Incidence is the angle at which the sun's rays strike the earth's surface
• When the angle of incidence is higher, the sun's rays are more concentrated on that area.
• Angle of incidence is high especially in the tropics (Tropic of Cancer and Capricorn) which is located 23.5°N and 23.5°S respectively.

Watch the video below to gain a better understanding of how latitude affects temperature (i.e. How the sun's rays reach the earth's surface at different angles and affects temperature).

(Stop at the 2 minute mark of the video)

Click on the link below to answer the quiz to test your understanding :)

https://docs.google.com/forms/d/1p9-P9YwbjWATjvRXveAo_VrU6gvMVBKaae6KFHsOEO4/viewform

Click on the images below to check if you managed to get the correct answers to the quiz :)