STEM与日常科技·英语30篇（6）
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Why Some Clouds Produce Rain While Others Stay Dry Despite Similar Appearance
为何外观相似的云朵有的降雨、有的却始终干燥
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Rain formation requires cloud droplets to grow large enough to overcome updrafts and fall as precipitation.
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Collision-coalescence dominates in warm clouds, where larger droplets absorb smaller ones during turbulent mixing.
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In cold clouds, the Bergeron process prevails: ice crystals grow at the expense of supercooled water droplets.
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Scientists use Doppler radar to detect vertical air motion and particle phase inside clouds remotely.
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Aerosol concentration determines initial droplet count—too many tiny droplets inhibit growth to raindrop size.
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Cloud base height and temperature profile affect whether freezing nuclei trigger ice formation early in development.
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Satellite-derived microphysical data help refine weather models predicting drizzle versus downpour intensity.
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Even visually identical cumulus clouds may differ internally in droplet distribution and updraft velocity.
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Field campaigns deploy instrumented aircraft to sample cloud chemistry and ice nucleation activity directly.
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Understanding these variables improves flood forecasting and reveals how pollution subtly reshapes regional hydrology.