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STEM Light Read: Why Dew Forms on Cool Grass But Not on Warm Pavement (2026-D012)
STEM轻科普延展阅读·独立成篇（2026-D012）
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Dew forms when moist air cools overnight and reaches its dew point temperature.
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Grass loses heat quickly by radiation, so its surface drops below the dew point.
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Pavement stays warmer because it stores and slowly releases daytime heat.
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This temperature difference explains why dew collects on grass but not on roads.
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The process requires calm air, clear skies, and high humidity near the ground.
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Dew is pure water, since condensation leaves salts and pollutants behind.
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Unlike rain, dew forms directly from vapor without passing through clouds.
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Scientists measure dew points to predict fog, frost, and comfort levels outdoors.
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In dry climates, dew can be a vital water source for insects and desert plants.
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Understanding dew helps engineers design better condensation-based water harvesters.