Geography – Atmospheric processes and global climate change | e-Consult
Atmospheric processes and global climate change (1 questions)
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Precipitation forms when water vapour in the atmosphere condenses to form cloud droplets, which then grow large enough to fall as rain, snow, sleet, or hail. The process involves several key stages:
- Evaporation: Solar radiation provides the energy for water to change from liquid to gas, increasing the amount of water vapour in the atmosphere.
- Transpiration: Plants release water vapour into the atmosphere through their leaves.
- Condensation: As warm, moist air rises, it cools. This cooling reduces the air's ability to hold water vapour, causing the vapour to condense into liquid water or ice crystals. Condensation requires condensation nuclei – tiny particles like dust, pollen, salt, and smoke – for the water vapour to condense onto.
- Cloud Formation: Condensation nuclei provide a surface for water vapour to condense, forming cloud droplets. These droplets collide and coalesce, growing larger.
- Precipitation: When the cloud droplets become heavy enough, they fall to the Earth's surface as precipitation. The type of precipitation depends on the temperature profile of the atmosphere.
Factors influencing precipitation type:
- Temperature: The temperature of the atmosphere determines whether precipitation falls as rain, snow, sleet, or hail. If the entire atmospheric column is below 0°C, precipitation will be snow. If the air is warm enough to melt snow before it reaches the ground, it will fall as rain. If snow melts and refreezes into ice pellets before reaching the ground, it becomes sleet. Hail forms in strong thunderstorms with strong updrafts that repeatedly carry ice particles into freezing levels.
- Air Pressure: Low-pressure systems are associated with rising air, which cools and leads to condensation and precipitation.
- Wind Systems: Wind systems can transport moist air to different locations, influencing the type and amount of precipitation.
Different types of precipitation are formed through variations in these processes. For example, rain forms when water droplets in clouds grow large enough to overcome air resistance and fall. Snow forms when ice crystals in clouds grow and fall. Sleet forms when snow melts and refreezes as it falls through a layer of freezing air.