Rainfall is defined as precipitation that falls from the atmosphere to the ground. It can be in the form of liquid rain, frozen rain, or sleet. Snowfall is not considered rainfall because it doesn’t fall from the atmosphere to the ground.
Precipitation occurs when water vapor in the atmosphere condenses into tiny droplets or ice crystals and then falls to the earth’s surface. The type of precipitation that forms depends on temperature and atmospheric conditions.
Liquid rain forms when the air temperature is above freezing and there are enough water vapor molecules in the air to saturate it. At this point, water vapor starts to condense onto small particles in the atmosphere, such as dust or salt, which act as “condensation nuclei”. These droplets grow larger and heavier until they eventually fall from clouds as raindrops.
Frozen rain, also known as sleet, forms when liquid raindrops freeze into ice pellets while still in the clouds. Sleet generally occurs when warm air at lower altitudes rises and mixes with colder air aloft, causing precipitation to fall through a layer of cold air before reaching the ground.
Snow develops differently than both rain and sleet-it begins as very light flakes high up in cumulonimbus clouds where temperatures are well below freezing (-15°C). Because snowflakes are so light, they can be carried long distances by winds before finally falling from the sky as snowfall. The biggest difference between snowflakes and other types of precipitation is their shape-snowflakes have six symmetrical sides due to crystallization processes that occur while they are forming high in clouds.
All three types of precipitation-rain, sleet, and snow-are important components of Earth’s hydrological cycle and play a role in supporting life on our planet