♨️ Steam & Condensation — Phase Transition
Water vapour molecules rise and cool. When temperature drops below the dew point Td, molecules lose enough kinetic energy to form liquid droplets — condensation. Relative humidity RH = e/es(T) where es is the saturation vapour pressure (Clausius-Clapeyron).
Scenario
Atmosphere
Stats
What this simulation shows
Vapour molecules (white dots) are emitted from the warm surface at the bottom. They rise against gravity with random Brownian motion. The background colour gradient shows the temperature — warm at the bottom, cold at the top. When a molecule's height causes the local temperature to drop below the dew point, it condenses into a droplet (blue dot) that grows as more molecules join it. Droplets large enough fall as rain (green).
The cloud base height is where saturation is reached: zLCL ≈ 125 · (T − Td) metres. Increasing humidity lowers the cloud base; increasing the lapse rate raises it.
Did you know?
The Clausius–Clapeyron equation describes how saturation vapour pressure doubles roughly every 10 °C. This is why a 4 °C warmer atmosphere can hold ~28% more water vapour — intensifying rainfall events in a changing climate.