Air masses
An air mass is a big mass of air that forms on top of its source over a period. They have different characteristics of moisture and temperature. Their places of origin define air masses as opposed to where they are currently are as asserted by Simpkins (2017). Wind direction is the variable to denote which air mass is located in a particular region because its name defines the source of origin from where the air comes from. Colder air masses are referred to as polar or arctic while warmer air masses are called tropical.
Cold air masses include Arctic, Antarctic, and polar air masses. This is because they develop on top of ice and snow that has covered the ground. Arctic air mass is the coldest. Continental Arctic has frigid temperatures with tiny amounts of moisture. They originate from the Arctic Ocean in the winter. Maritime Arctic originates from the same source but is lesser dry and cold. Polar air masses usually develop over regions in higher altitudes and are shallower compared to arctic air masses. Polar air masses are known to lose stability when they acquire moisture. On the other hand, tropical and equatorial air masses become hotter as they develop over lower latitudes. According to Simpkins (2017), m aritime tropical air masses are also referred to as trade air masses. The monsoon air masses are moist and unstable. Superior air masses are normally dry and hardly reach the ground. Continental polar air masses are cold and dry due to their source in the continental region. They originate from high latitudes and are known to bring cold conditions accompanied by a dry and clear weather witnessed on a winter day or a dry and moderately warm day experienced during summers ( Simpkins, 2017).
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Weather Fronts
It is the boundary that separates two air masses. This separation is based on the densities of the two air masses. Air masses at a front usually differ in humidity and temperature. Cold fronts are a precursor of a thunderstorm and a severe weather while warm fronts are a precursor of precipitation and fog. Cold fronts conventionally move from west to east while warm fronts move polewards. Factors that can slow down the movement of fronts include mountains and warm bodies. Cold fronts move faster than warm fronts. This is because of the greater density in warm fronts. An occluded front form when a cold front overtakes a warm front and mostly forms in regions of low pressure. Stationary fronts do not move and exhibit a wave-like motion in their locality.
A dry line is a special type of a weather front. It is a boundary between air masses with a significant moisture difference. When a cold front moves under a warm front, air is lifted and condensed into clouds after that leading to a form of precipitation called a convective precipitation. This includes showers accompanied by a thunderstorm and other unstable weather (Schultz et al. 2014). When the difference in temperature between the two air masses involved is extremely huge, accompanied by turbulence, tornadoes may occur. In an area with warm fronts, storms do not occur frequently; this is because as the warm air ascends over the cold air, the process is gradual. Stationary fronts will stay together for some time without any considerable weather change and soon enough they will entangle. Thunderstorm and earthquakes arise when there is a sudden, quick and dramatic rise of warm air when a denser cold air mass moves in as asserted by Schultz et al. (2014). Therefore, air masses and weather fronts are a vital geographical phenomenon that affects the weather of a given region.
References
Schultz, D. M., Richardson, Y. P., Markowski, P. M., & Doswell III, C. A. (2014). Tornadoes in the central United States and the "Clash of Air Masses." Bulletin of American Meteorological Society , 95 (11), 1704-1712.
Simpkins, G. (2017). Hydro climate: Stronger atmospheric fronts. Nature Climate Change , 7 (2), 96-96.
