Cloud Development

Clouds are aggregates of visible water droplets or ice particles formed and sustained by the adiabatic lifting and cooling of air until saturation, followed by condensation or deposition.
Dew point is the temperature at which an air parcel, when lifted adiabatically, becomes saturated and water vapour condenses into water droplets.
Lifting Condensation Level (LCL) is the height at which cloud formation begins due to condensation at the dew point.
The Lifting Condensation Level indicates the cloud base of convective clouds.

Cloud base can be approximated by the difference between the surface temperature and the dew point.
A larger difference between surface temperature and dew point indicates a higher cloud base.
Cloud Base (ft) = (Surface Temperature − Dew Point) × 400
High surface temperatures generally produce higher cloud bases and higher cloud tops, especially around 1500 LMT, due to intense surface heating.

A cloud stops growing vertically when there is a sharp reduction in relative humidity.
Humidity levels are measured using a radiosonde and plotted on a thermodynamic graph.
The height at which the SALR curve meets the ELR curve indicates an inversion layer.
At the inversion layer, the saturated air parcel is no longer warmer than the surrounding environment and therefore stops rising.
This height generally represents the cloud top of a Cumulonimbus (Cb) cloud.

Layered clouds form at heights where the ELR curve meets the Dew Point curve on a height-temperature graph.
These clouds may be Stratocumulus (Sc) or Altostratus (As).
Wind-induced turbulent mixing carries moisture to the top of the mixing layer, just below the inversion layer, producing layered clouds.
Surface friction caused by hills and buildings forces air to rise, often producing small cumuliform clouds over built-up areas.

Cumuliform clouds form due to localized or large-scale vertical motion of air caused by surface heating.
Trigger Temperature is the surface temperature at which the atmosphere becomes warm enough for an air parcel to rise to the Lifting Condensation Level and cool to its dew point.
Below the trigger temperature, the air parcel reaches the environmental temperature before reaching the dew point and therefore does not become saturated or form clouds.

Velocity convergence refers to the net horizontal inflow of air.
Accumulated air rises at the surface and may produce either ascent or descent at higher levels.
Air converges in areas of low pressure, cyclones and depressions.
Velocity divergence refers to the net horizontal outflow of air.
Air generally diverges from high-pressure areas and anticyclonic circulations.

Convergence is the accumulation of air caused by inflow from the surrounding areas.
The converging air is forced to rise because of the accumulation of air at a point or along a line.
On islands and peninsulas, sea breezes from different directions converge, causing strong upward motion and the formation of cumulus clouds.

Large-scale low-pressure systems draw air from surrounding high-pressure areas.
This convergence forces air to rise, resulting in the development of vertically growing clouds.

Orographic ascent refers to the forced lifting of air over mountainous terrain, especially along coastlines.
Moist air forced to rise over coastal mountains cools adiabatically, producing clouds and precipitation on the windward slopes.
The presence of lenticular clouds over mountains indicates turbulence and an increased risk of icing.

Contrails are condensation trails produced due to aerodynamic pressure reduction around wingtips, causing condensation of atmospheric moisture.
Exhaust trails form when water vapour from aircraft engines condenses at high altitudes, typically above the freezing level (around 9 km).
Distrails occur when the heat from aircraft exhaust evaporates cloud droplets, creating clear paths through clouds.
Mintra Level is the altitude below which contrails cannot form.
Drytra Level is the altitude at which contrails can form solely from exhaust moisture, even when the relative humidity is zero.