Final answer:
The statement is true; air masses form over regions where the air can remain stable for an extended period to take on uniform characteristics, which can include temperature and humidity. The stability of air masses is influenced by the long distances they travel over surfaces like water and by the various layers of the atmosphere, such as the troposphere where weather phenomena occur.
Step-by-step explanation:
True, air masses do form over regions where the air is stable for a sufficient length of time to acquire the same characteristics. Air masses take on properties such as temperature and humidity, which are similar to the surface over which they develop. For instance, air flowing long distances over water tends to be especially stable, making it a good candidate for forming an air mass with distinct characteristics. When considering the density of air, it is important to note that it decreases with altitude in an exponential manner relative to the constant temperature of the column of air, although in practice, temperature does vary with altitude. The structure of the atmosphere, which includes the troposphere, stratosphere, mesosphere, and ionosphere, plays a vital role in weather patterns and climate. The troposphere is especially relevant as it is the lowest layer where weather occurs, and is characterized by convection currents that shape weather systems, as well as the distribution and characteristics of air masses.