Cumulus cloud formation

E. Summary of Cooling Processes During Cumulus Cloud Formation and Resulting Thermal Instability... 

Watch for developing thunderstorms. Thunderstorms occur year-round. As the sun heats the air, pockets of warmer air start to rise, and dark, thick cumulus clouds form. Continued heating can cause these clouds to grow vertically into massive formations that often indicate a developing thunderstorm. 

Figure 3.45. Cumulus clouds are created by adiabatic expansion, and thus cooling, of air in thermal upwind when the air temperature has fallen to the dew point, the water vapour will condense into this well-known cloud formation.

In the formation of the puffy, fair-weather clouds known as cumulus clouds, solar heating of the ground warms the adjacent air, and bubbles of this warmed air rise due to buoyancy, their temperature decreasing with altitude according to the dry adiabatic lapse rate (Fig. 4.8). At the altitude where the dew point is reached and condensation begins, a cloud forms, and the stability of the air decreases as the air begins to follow a wet adiabat. Instability can lead to extensive vertical development of the cloud and strong upward air currents within the cloud. On hot summer days, this can lead to the production of a late-afternoon thunderstorm. 

Condensation is the main route leading to the formation of finely dispersed aerosols in nature and industry. The formation of cumulus (composed of water droplets) and cirrus (composed of ice crystals) clouds mainly starts with heterogeneous nucleation on fine dusts and microcrystals of salt. These microcrystals form when splashes of sea water are dried and raised to high layers of atmosphere by convection air streams. 

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