Final answer:
Fountains of gently dripping water cool courtyards in hot, dry climates through evaporative cooling. This process leverages water's ability to absorb heat energy during evaporation, reducing the temperature of the surrounding air.
Step-by-step explanation:
The use of gently dripping water in fountains to cool courtyards in hot and dry climates is an example of evaporative cooling, a physical process that relies on water's high specific heat capacity. Water is known to absorb substantial amounts of heat energy when it evaporates. This removal of heat from the environment as water transitions from liquid to vapor leads to a cooling effect in the surrounding area.
In hot regions, such as those with desert climates, there are drastic temperature differences between day and night due to the lack of water bodies which can moderate the climate. By introducing fountains and water features, the evaporation process is encouraged. As the water evaporates, it absorbs heat from the nearby air, thus lowering the temperature and cooling the atmosphere of the courtyard or enclosed space.
This is similar to ancient cooling systems, like the qanat, which used cold mountain water to create a cooler environment. The same principle explains why in humid climates with many bodies of water, like Florida, extreme high temperatures are uncommon. The abundance of water limits temperature rises through constant evaporation.