Answer:
Explanation:
An air mass is a large body of air that exhibits uniform temperature and moisture characteristics and helps to determine the weather within an area. Warm air masses tend to form over oceans in warm-temperature regions of the tropics and sub-tropics, while cold air masses tend to form over land in cold-weather regions nearer the poles. The cold air masses that form at the poles move toward the equator, while the warm air masses that form at the equator move toward the poles. These air masses can undergo gradual, but significant, changes as they pass over warmer or colder land surfaces encountering different types of air. These boundary lines are called fronts.
Cold fronts occur when a cold air mass moves into warmer air. Since cold air is heavier than warm air, the incoming colder air forms a wedge that displaces the warm, and often moist, air at the surface. As the warm moist air rises, towering clouds often form releasing energy in the form of brief, intense rain storms with high winds and lightning. On the other hand, warm fronts will ride up and over cold air near the surface. These fronts can also cause clouds and rain, but they tend to be less violent and longer lasting.
Air pressure is determined by how much the air weighs in a given space. Pressure varies with altitude, with denser air residing in lower altitudes and lighter air in higher altitudes. This is caused by the Earth’s gravity—its strength decreases the farther away from the center of the planet, therefore it holds fewer molecules together in the same amount of space. Air pressure is also a function of temperature and density; differences in pressure can be an important weather maker. As air descends, it warms, inhibiting cloud formation which is often associated with good weather. Air rises in areas where the pressure at the surface is low. As it rises, the air cools and the humidity condenses to form clouds and precipitation. The centers of all storms are areas of low pressure; therefore, low pressure is often associated with bad weather.
