why, even on bodies of water with no boats present, is the water often much more calm in the evening and early morning than during the day?

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why, even on bodies of water with no boats present, is the water often much more calm in the evening and early morning than during the day?

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Water choppiness is driven by wind blowing over the water. The wind hits the top of the water, which is pushed by the wind in one direction but held by drag against the rest of the water in the other direction. The top of the water is pushed up, which creates more surface area for the wind to hit, which pushes it harder, which lifts it up, and so on to the limits of the strength of the wind and gravity and water tension and so on. More wind – especially shifting and chaotic wind – means more waves.

Wind is driven by a difference in air temperature. Hot air is less dense than cold air, so the cold air tends to flow under the hot air and push it upwards. The hot air cools down in the upper atmosphere and the cold air warms up from the heat radiating off of the ground, and the cycle continues. As the hot air rises it leaves empty space that gets filled by either cold air moving in or hot air being shoved in that direction by cold air moving in. The greater the difference in temperature between two areas, the harder the wind will blow and vice versa.

During the day the Sun will warm the ground, but it does so unevenly. Water can absorb a ton of heat before radiating it out, and will continue to radiate that heat for a long time like a battery. Water is also reflective so it will absorb less heat than dark dirt or rock. There are a lot of other factors like plant life and the color of the ground and what natural features are around to block or direct wind to cool or warm an area more than another, shade from trees or natural formations like mountains…

Early at night, the ground and water are still warm from the sunlight during the day. Later in the morning, the Sun has started to warm everything up. Shortly after noon tends to be a bit more calm because *everything* is hot – the ground is as hot as it will be for the day and is radiating heat out about as fast as the Sun is heating it up. Early morning is when there is the smallest difference in temperature for a given region, though. The ground has cooled as much as it can and there has been no sunlight to warm it up. The air is cool without any sunlight or warmth from the ground. The Sun may be rising, but it hasn’t risen enough to really start warming anything up. *Everything* is cool, so there’s not much difference between any areas to create a lot of wind.

Without wind to pick up the waves, the water is also very calm.