On a sunny afternoon at Chennai's Marina Beach, Harleen feels a cool breeze blowing in from the sea
On a sunny afternoon at Chennai's Marina Beach, Harleen feels a cool breeze blowing in from the sea. She says it happens because the land heats up faster than the sea: the hot air above the land rises, the pressure there drops, and cooler air from over the sea moves in to take its place. Devansh says the wind should blow from the land out to sea in the afternoon, because the hot land pushes its hot air outward. Whose explanation matches the breeze Harleen feels?
Who do you think is right? Pick one.
The answer: Harleen is right, wind blows from higher pressure towards lower pressure
Why
Devansh is correct that the land is the hot part of the picture in the afternoon — but hot air doesn't get pushed sideways out to sea; it rises. Warm air expands, becomes lighter and goes up, which leaves lower air pressure near the ground over the land. Over the sea, the water warms up much more slowly, so the air there stays cooler and its pressure stays higher. Air moves from a region of higher pressure to one of lower pressure, so the cool sea air flows in towards the land — the sea breeze Harleen feels. At night it flips: the land cools faster than the sea, and the breeze blows from land to sea. Test: hold a strip of tissue paper a little above a pan of hot water — it flutters upward, because warm air rises rather than spreading out sideways. Harleen is right: the daytime breeze blows from sea to land because hot air rising over the land leaves lower pressure there.
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