Hi narisha, you probably know that water can be in the form of a liquid, or a solid (ice), but it can also be a gas (water vapour). Almost all the air around us is moist, meaning that it contains water as vapour. The amount of water in the air is measured as humidity, which you hear about on the news. High humidity is about 45-50% saturation of the air with water vapour, and it’s one of those days when your hair gets all frizzy.
Warm air can hold more of this water vapour than cold air can. So as warm air moves upward in the atmosphere and becomes cold, the water vapour condenses to form tiny droplets. This is what a cloud is; a mass of tiny droplets of water and ice crystals. This cloud mass actually weighs a couple of tonnes (similar to an elephant) but it is spread out over a large area, and the water droplets are so small, that warm air rising from the surface of the Earth is able to keep it afloat.
To actually make rain, the droplets of water in this cloud have to become heavy enough that the warm air currents can no longer keep them afloat. This happens when the air below the cloud cools down, so more water vapour will condense from this air, the tiny droplets will clump together and become heavier, and they will begin to fall as rain.
So you might wonder, how does it rain on a warm day if the air needs to be cool to form droplets? On a warm day, air at ground level will be heated up and start to rise (hot air rises because it is less dense than cold air). Because this air is warm it can hold a lot of water vapour. As the air continues to rise it will get to a point in the atmosphere where it starts to cool (the higher up you go, the colder it is), and because it is holding so much vapour, a lot of droplets will condense which may lead to the kind of torrential downpour you sometimes get in Summer.
Hi narisha, you probably know that water can be in the form of a liquid, or a solid (ice), but it can also be a gas (water vapour). Almost all the air around us is moist, meaning that it contains water as vapour. The amount of water in the air is measured as humidity, which you hear about on the news. High humidity is about 45-50% saturation of the air with water vapour, and it’s one of those days when your hair gets all frizzy.
Warm air can hold more of this water vapour than cold air can. So as warm air moves upward in the atmosphere and becomes cold, the water vapour condenses to form tiny droplets. This is what a cloud is; a mass of tiny droplets of water and ice crystals. This cloud mass actually weighs a couple of tonnes (similar to an elephant) but it is spread out over a large area, and the water droplets are so small, that warm air rising from the surface of the Earth is able to keep it afloat.
To actually make rain, the droplets of water in this cloud have to become heavy enough that the warm air currents can no longer keep them afloat. This happens when the air below the cloud cools down, so more water vapour will condense from this air, the tiny droplets will clump together and become heavier, and they will begin to fall as rain.
So you might wonder, how does it rain on a warm day if the air needs to be cool to form droplets? On a warm day, air at ground level will be heated up and start to rise (hot air rises because it is less dense than cold air). Because this air is warm it can hold a lot of water vapour. As the air continues to rise it will get to a point in the atmosphere where it starts to cool (the higher up you go, the colder it is), and because it is holding so much vapour, a lot of droplets will condense which may lead to the kind of torrential downpour you sometimes get in Summer.
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