Earth's Atmosphere: The Water Cycle

Earth’s Atmosphere: The Water Cycle

• The water cycle, or hydrological cycle, plays a crucial role in Earth’s atmosphere. It describes how water evaporates from the surface of the Earth, rises into the atmosphere, cools and condenses into clouds, and falls back to the surface as precipitation.

• Evaporation: This process occurs when the sun heats the Earth’s surface water, which then turns into a gas and rises into the atmosphere.

• Condensation: The water vapour in the atmosphere cools down and changes back into liquid droplets, forming clouds. This is the reverse of evaporation.

• Precipitation: The water droplets in the clouds become too heavy to stay in the cloud, so they fall back to the earth’s surface. This can take many forms, such as rain, sleet or snow.

• Runoff and Infiltration: Once the water returns to the earth’s surface, it either flows along the surface, known as runoff, and ends up in rivers, lakes or the sea; or it soaks into the ground, a process known as infiltration, replenishing groundwater supplies.

• Transpiration: This is the process of water movement through a plant and its evaporation from aerial parts, such as leaves, stems and flowers. The water vapour leaves the plant and enters the atmosphere.

• Interception: A small proportion of precipitation lands on vegetation before eventually evaporating back into the atmosphere or dripping onto the ground.

• The sun’s energy drives the water cycle, and all the water on Earth is reused in this continuous cycle.

• The Water Cycle directly impacts global climate patterns and weather phenomena. As part of climatic systems, an understanding of this is vital in predicting weather and mitigating the impacts of climate change.

• It’s crucial to understanding the water cycle as it is inextricably linked with processes such as weather formation, shaping of the Earth’s geological features, and ensuring water availability for human survival.

• Human activities, such as deforestation and burning fossil fuels, can affect the water cycle by influencing the amount of water vapour in the air and subsequently the climate.

• Relative humidity is the amount of moisture in the air compared to the maximum amount of moisture that air could hold at a particular temperature. Also, the relative humidity plays a significant role in the occurrence of cloud formation and precipitation.

• Distillation is a laboratory-scale model of the water cycle, and it is a technique that is used to purify a liquid or separate liquid mixtures based on differences in their boiling points.