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Absolute humidity is a measure of the actual amount of water vapor present in the air, expressed as the mass of water vapor per unit volume of air. In this context, it is described in grams per cubic meter (\[\text{g/m}^3\]). When you look at absolute humidity, it tells you how much moisture is in the air at a given moment, regardless of temperature.

To understand this better, consider the initial condition in the exercise. The air at \[30^{\circ} \text{C}\] can hold a moisture content of \[30 \, \text{g/m}^3\]. This means every cubic meter of that air contains 30 grams of water vapor. As the temperature drops to \[20^{\circ} \text{C}\], absolute humidity decreases to \[16 \, \text{g/m}^3\] because cooler air can hold less water vapor. This decrease in humidity is important because it leads to the process of condensation.

Saturated vapour is a state where the air contains the maximum possible amount of water vapor for a given temperature. Beyond this point, any additional water vapor will start to condense into liquid water. In other words, the air has reached its capacity to hold moisture at that temperature. Saturated vapor pressure rises with temperature, meaning warm air can hold more water vapor than cold air.

In the provided exercise, initially, the air at \[30^{\circ} \text{C}\] is saturated with water vapor. As the temperature decreases to \[20^{\circ} \text{C}\], the capacity of the air to hold water vapor decreases, and any excess moisture will condense as liquid water. This is the principle behind cloud formation and precipitation in weather systems.

Temperature change plays a crucial role in determining the ability of air to hold water vapor. As temperature increases, air can hold more water vapor, and as temperature decreases, this capacity lessens. This relationship is depicted through the concept of saturation, where, at a certain temperature, air can no longer hold additional water vapor, resulting in condensation.

In the exercise, cooling the air from \[30^{\circ} \text{C}\] to \[20^{\circ} \text{C}\] causes a reduction in the amount of water vapor the air can hold. Since the initial amount of vapor was at the saturation limit for \[30^{\circ} \text{C}\], decreasing the temperature leads to condensation; the air at \[20^{\circ} \text{C}\] can only retain a smaller amount of vapor (as determined by the new absolute humidity), and the surplus is released as liquid water. This process is crucial in understanding not only atmospheric processes but also how humidity affects our daily weather.