TMJC 2025 JC1H2 C2 Lecture 2 Factors Affecting TC Temperature

Higher 2 (9173) Tropical Environments C2 Lecture 2 Factors affecting Temperature in Tropical Climates 2025 Page 1 of 16 LECTURE OBJECTIVES 1. Discuss the dynamism of natural environments in the tropics • Discuss the various factors affecting temperature in the tropics INTRODUCTION The Earth is constantly receiving incoming heat energy from the sun in the form of insolation (incoming solar radiation). This energy influences our planet’s climate and weather and which, when converted by photosynthesis in green plants, supports all forms of life. This heat energy received from the sun must be balanced by outgoing heat energy radiated back into space from the Earth as otherwise the Earth will experience a continuous increase in temperature. Since the Earth does not experience a continuous increase i n temperature (human induced global warming excluded), this means that incoming energy is matched by outgoing energy from the earth. HOW IS ENERGY TRANSFERRED? Before we understand the radiation balance, we will need to first understand how heat energy is transferred. Heat energy can be transferred via 3 mechanisms (Fig. 1): (i) Conduction Conduction is the transfer of heat through matter by molecular activity . The energy is transferred through collisions from one molecule to another, with the heat flowing from the higher temperature to the lower temperature. Hence, direct contact of molecules is required. T his implies that land (solids) can conduct heat better than water bodies (liquids) which in turn, conduct heat better than air (gases). (ii) Convection Convection is the transfer of heat by circulation within a fluid (i.e. liquids like ocean, gases like air) where atoms and molecules are free to move about. On a global scale, convection in the atmosphere creates a huge world-wide air circulation which is responsible for the redistribution of heat. Redistribution of heat also occurs in the form of ocean currents. (iii) Radiation Unlike conduction and convection, radiation is the only process of heat transfer that does not require a medium (solid or fluid) to travel through. Radiation is the only mechanism of energy transfer through the vacuum of space and thus, radiation is the heat-transfer mechanism by which solar radiation reaches the Earth from the sun. Fig. 1 – Three mechanisms of heat transfer: conduction, convection, radiation

Page 2 of 16 WHAT IS THE EARTH’S ENERGY BUDGET/ RADIATION BALANCE? The radiation balance (also known as energy budget / heat budget) shows the equilibrium between incoming energy from the sun and outgoing energy from the Earth (Fig. 2). The radiation balance thus prevents, at least in the short term, significant rises or falls of the average temperature of the Earth. Fig. 2 - Incoming and outgoing radiation 30% of the earth’s incoming insolation is reflected and scattered back to space. The remaining 70% of the solar radiation that i