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Chapter 14

Types of Cloud.

Convection Cloud (continued).

As the rising air cools, its ability to hold water vapour is reduced. When the air cools enough to reach the dew point level any further cooling will result in the water vapour condensing into water particles (cloud).

As condensation takes place latent heat is given off. This latent heat reduces the cooling rate of the air by half. So once the air has become saturated and visible water particles appear (i.e. cloud), any further cooling will occur at 1.5 deg Celsius per 1,000ft rather than 3 deg Celsius. This is called the Saturated Adiabatic Lapse Rate (SALR).

Due to the detail on the following diagram, it is best viewed on a desktop browser.

In this example, you can see that conditions are unstable as the air temperature is consistently cooler than the temperature of the rising air. The example uses 11 degrees as a dew point and you can see that once the rising air reaches this temperature, the water vapour condenses into cloud. After this point, it will only cool at the SALR (1.5 deg Celsius per 1,000ft). Eventually, at 4,000ft, the air temperature matches that of the rising air and equilibrium is reached.

The type of cloud formed by convection is cumuliform.