Scattered visible light and microwave radar can used used to detect clouds and precipitation. Cloud formation in rising air can be simulated in the classroom by suddenly dropping the pressure in a glass chamber. The small cloud droplets formed in this way fall too slowly to ever reach the earth. There are two main mechanisms by which precipitation is generated from clouds. Collision coalescence occurs mainly over tropical oceans whereas the ice phase mechanism is more common and also more relevant to the practice of cloud seeding.

Air is able to hold a limited amount of water vapor, and that amount depends on the temperature of the air. When this saturation vapor pressure is exceeded, liquid water begins to condense and clouds form. There are several different types of clouds, some which rain and others which do not, and each with characteristics specific to it. Vortices are a particular type of cloud phenomenon in which there is a low pressure anomaly in the center of the cloud with rotating air around it, forming funnel clouds as seen in tornados.

The lapse rate describes the rate at which air cools with altitude. Atmospheric stability depends on the lapse rate. When an air parcel is lifted or lowered, it can continue to rise or descend based on the temperature of the surrounding air at the new altitude, which indicates an unstable atmosphere. Inversions can occur in the atmosphere, meaning the air near the ground will be cooler than air aloft. This type of temperature profile can cause air to be trapped near the Earth’s surface in a boundary layer, which can also lead to pollutants being trapped near the ground.

This lecture describes how pollutants mix in the atmosphere. Three cases are considered: confined mixing, unconfined mixing, and unconfined mixing with wind. In a confined volume, the concentration of pollutant in the air depends on the volume and the mass of the air present in the volume. Unconfined mixing is also known as diffusion, in which the pollutant disperses through the air from the source over time. When wind is considered, the pollutant disperses from the source in the direction of the wind. The change in temperature with height in the atmosphere is also discussed.

The hydrostatic law describes the weight of a fluid overlying a given area, or the pressure at a particular point. It can be used to calculate the approximate atmospheric mass over a particular area, or to calculate the change in pressure over a given change in altitude. A calculation of the pressure difference from the ground to the twelfth floor of Klein Biology Tower is found to agree well with measurements taken at both locations. The hydrostatic law also applies to pressure changes with depth in the ocean.

A simple model of the overall Earth’s heat budget is derived. The Earth is assumed to be in equilibrium with the input of solar radiation balanced by the output of infrared radiation emitted by the Earth’s surface. Using this model, the Earth’s surface temperature is calculated to be cooler than in reality due to the lack of an atmosphere and the greenhouse effect in the model.

Several experiments are performed using a water tank with an input flow of water and an output flow. These experiments demonstrate the concepts of equilibrium and steady-state in system analysis and are analogous to various Earth systems; lakes and rivers and the overall heat budget of the planet. The greenhouse effect in the atmosphere is a mechanism for increasing the heat input from the sun in the overall heat budget of the Earth system.

Pressure and density decrease exponentially with altitude in the atmosphere. This leads to buoyancy effects in the atmosphere when parcels of air are heated or cooled, or raised or lowered in the atmosphere. Temperature varies in a more complicated way with altitude in the atmosphere, with several inversions which occur at the boundaries of the various layers of the atmosphere. Solar radiation interacts differently with the gases that compose each layer of the atmosphere which affects which wavelengths of radiation are able to reach the surface of the Earth.

The Perfect Gas Law relates temperature, pressure, and density of gases in the atmosphere. It can be used to demonstrate why warm air rises, cool air sinks, and helium balloons float in the air. Buoyancy forces act in fluids (both water and air) when fluid is displaced by a parcel of a fluid with a different density. A combination of buoyancy force and the relationship given in the Ideal Gas Law govern the motion of parcels of gas in the atmosphere.

Despite the substantial change in the energy of individual orbitals, the overall pi-electron energy and orbital shape changes little upon linear conjugation of two double bonds. Conjugation energy of polyenes and allylic systems may be predicted by means of a semicircle mnemonic. The much greater stabilization in "aromatic" conjugated rings, and Hückel's 4n+2 rule, derive from alternating stabilization and destabilization of successive orbitals when the ends of a conjugated chain overlap as it is closed to form a ring. A circle mnemonic predicts orbital energies for conjugated rings.