The Sun emits energy mainly as shortwave radiation which reaches the surface. Hence the atmosphere is heated from below.

As we move upward, there is less air above us, so atmospheric pressure decreases with height:

The Troposhpere is mainly heated through surface hence temprature also decreases with heigh. The rate at which temperature decreases with height is called the environmental lapse rate:

Surface heating warms the air near the ground, making it lighter than the surrounding air:

The warm air starts rising upward. As the air rises higher, pressure decreases, so the air expands and becomes cooler. Upward motion is represented by:

Negative ω means rising air.

As the rising air cools, it can hold less moisture. Relative humidity increases until the air becomes fully saturated at the Lifting Condensation Level (LCL). Cloud droplets begin to form and latent heat is released.

This equation shows that condensation depends on: 1. upward motion (ω < 0) 2. how rapidly saturation humidity changes with height (dqₛ/dp). As air rises and cools, the maximum moisture the air can hold decreases. Excess water vapour then condenses into cloud droplets. Total upward motion comes from different processes acting together given by:

Surface heating is not the same everywhere. Some regions become warmer than others. Warm air near the surface becomes lighter and starts rising upward. Nearby air flows inward to replace the rising air, creating low-level convergence and convective updrafts:

At the same time, winds can transport warm moist air from one region to another. This is called warm air advection. When warm air moves into a region, the atmospheric column expands vertically and helps generate large-scale upward motion This strengthens regional ascent, cloud growth, and moisture transport:

Large-scale winds in the atmosphere create Rossby waves, troughs, jet streams, and cyclonic circulation. These systems spin the air cyclonically and transport higher vorticity into a region. This process is called positive vorticity advection (PVA). PVA disturbs the atmospheric balance and helps force air to rise upward:

As the air continues to rise, it cools further and more water vapour condenses into cloud droplets. Condensation becomes stronger, latent heat release increases, and cumulus clouds grow vertically into deeper convective clouds.

As more condensation occurs, latent heat is released into the rising air parcel. This warms the parcel, making it lighter and less dense than the surrounding environment. The parcel now rises even faster:

This additional upward motion strengthens condensation and cloud growth even more. This is called a positive convective feedback, where rising motion and condensation continuously reinforce each other.

After clouds begin to form at the LCL, condensation releases latent heat into the rising air parcel. This added heat slows down the cooling of the parcel, so it stays warmer than the surrounding atmosphere.

Since the parcel is now warmer and lighter than the surrounding air, buoyancy becomes positive again and the air rises more rapidly. Above the Level of Free Convection (LFC), the parcel can continue rising on its own without extra lifting. This leads to deep cloud growth, strong convection, and eventually rainfall formation.