[Geography Notes] on Updraft Pdf for Exam

There are two terms commonly and widely used in meteorology with respect to air currents. They are updraft/vertical draft and downdraft. An updraft is a small-scale rising air current usually within a cloud. Similarly, a downdraft is a downward moving current of air within a cloud. Both these phenomena can be caused due to several factors. A very simple example of the updraft is the upward movement of the warm air from the surface towards the sky. Similarly, the example of downdraft is the downward movement of the cool air from the skies to the surface of the earth. 

Causes of an Updraft

During the daytime because of the radiation being reflected by the ground, the air above the surface gets heated. Local daytime heating makes the surface warmer and since the air gets warmer it gets less dense than the cool air above it. Because of this relative difference in the density, the warmer air begins to ascend upwards from the surface and is replaced by the cooler air which descends towards the surface. This movement of the warm air is known as thermal updraft because there is an updraft of warm air. The updraft is also created because of the turbulence that occurs when an air current passes over the barriers of topography such as the mountains. There are also common cases of updrafts occurring in thunderstorms as well. Such a type of updraft is known as thunderstorm updraft.

The updrafts are especially important as they play a significant role in the development of a storm. Especially during the early stages of a storm the warm air rising because of thermal updraft reaches the level when the condensation starts which supports the starting of the precipitation. With the cooling and falling of the precipitation in a mature storm, both the updrafts and downdrafts are caused. These drafts are also caused by the low pressure and high-pressure regions. Low-pressure regions attract large volumes of air which as it rises upward causes an updraft. Sometimes there is a rotation of the air current while moving upwards towards a low-pressure region or until the warm air of a thermal updraft encounters an air current with lower density, which comes to be known as rotating updraft.

Effects of Updrafts

Whenever there is a huge amount of moist and wet air that forms an updraft, it can lead to phenomena such as cyclones or tornadoes. For example, a supercell updraft is a thunderstorm that is caused by the presence of a deep and persistent rotating updraft. Whenever a thermal updraft which consists of warm air goes up away from the surface it cools down and later precipitates which mostly leads to rainfall because of a phenomenon known as convection. Thus, a convective updraft is a phenomenon causing rainfall in most cases. Not only, updrafts but such natural phenomena are also caused because of the downdrafts as well. Whenever there is a downdraft in huge amounts and vigorous speed it is known as downburst or microburst which has the capability to cause a tornado. 

Many times there are plenty of accidents as well caused because of thermal updraft/convective updraft, thunderstorm updraft, or a rotating updraft. These updrafts and downdrafts are a huge problem for flight travel and are major contributors to airplane crashes even during take-offs and landing. An example of such an incident is the crash of Delta Airlines Flight 191 during its final landing at the Dallas International Airport in 1985. 

Conclusion

As is clear from the article, an updraft or a downdraft is a natural phenomenon occurring because of the movement of air currents upward or downward respectively. These phenomena are responsible for a lot of natural activities such as rainfall, thunderstorms, tornadoes, or a supercell. Because of the turbulence that is created in the atmosphere because of such phenomena they are known for bad weather conditions and are grave risks to flight travels and also can cause severe natural calamities as well. An image of an updraft is shown below: