Cloud Formation Types (2D)

Cloud Type

Atmosphere

Surface temperature 24°C

Relative humidity 55%

Instability (growth rate) 1.0×

Warm thermals rise, cool, and condense at the lifting condensation level.

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Cloud base (LCL)

0.0 km

Altitude family

Low

Dew point (approx.)

15°C

Phase

Growing

How it works

Rising air cools at the dry adiabatic lapse rate (~9.8°C/km). It becomes a cloud once it cools to its dew point — the lifting condensation level (LCL). A common field estimate: LCL height (m) ≈ 125 × (surface temperature − dew point, °C); dew point itself drops roughly (100 − RH)/5 °C below the air temperature. Raise humidity or lower temperature and the cloud base drops closer to the ground; dry, hot air pushes it much higher.

Cumulus forms where isolated thermals punch through the LCL and stop rising a short way up — flat-bottomed, cauliflower-topped, confined to the low family (0–2 km). Stratus forms when a whole shallow layer is lifted gently and uniformly, producing a featureless grey sheet rather than discrete puffs, also in the low family. Cirrus forms independently of surface humidity: at 7–13 km the air is so cold that any moisture freezes directly into ice crystals, which strong upper winds shear into wispy streaks. Cumulonimbus begins as ordinary cumulus but, given enough instability (steep environmental lapse rate/CAPE), the thermal keeps overshooting through the middle and high families until it hits the stable stratosphere, where it spreads sideways into the classic anvil.

Cumulus — puffy, flat base Stratus — flat grey sheet Cirrus — high wispy streaks Cumulonimbus — anvil tower