Mountain meteorology is a discipline of science that focuses on the study of the effects of mountains on the atmosphere. The mountain effects on the atmosphere range over all scales of motion that include small scales of motion like turbulence, local scales, such as cloud formation on individual peaks and ranges, and global scales like the monsoons of the Asia and North America (Shapiro, 2008). There exist various weather related phenomena brought about by the presence of mountains in regions across the world. The joint effects of mountains or hills are perceived as relating to the blocking of air flow. The blockage of air flow can be explained in such a way: in the event of sufficient wind, and the air meets a huge obstacle and is therefore forced to either go around the obstacle or over the barrier that eventually causes waves in the flow of air (Kouznetsov, 2012). The waves generated as a result of air being blocked by an obstacle, mountain or hill, depict similar tendencies with those seen when a river washes over a boulder. The presence of the mountain ranges like the Sierras in North and South America places an obstacle in the path of the westerly winds that prevail in the middle latitudes.
The katabatic wind flows demonstrate a natural Antarctic specialty. The katabatic winds always occur above a cold sloped surface, and the winds happen when cold air on the top of a mountainous region or glacier begins to descend because of its higher density than that of the milder air at the lower part of the mountain (Doodge, 2010). The gravity concept explains the reason behind the cold air accelerating down the mountain to the point where in extreme cases, like in Antarctica, the winds exhibit potential to reach the levels of hurricane forces. The katabatic flows in Antarctica have a geographical explanation as being formed when the cold air masses start descending onto the ice cap to spread along the ground surface. The descending cold air masses meet nothing along their path to stop them, and this leads to the formation of sheet-like rivers of air and the blowing of snow. As the katabatic winds flow down the ice cap, their velocity increases, and the Coriolis force declines the flow of air from the downhill direction (Doodge, 2010). The blowing of snow across the ice cap makes it seem like one is in a relentless storm, but the odd phenomenon in such a scenario is that when one looks up, the sky is mostly sunny and blue with no signs of an impending storm. The katabatic flows maintain their air flow for quite a lengthy period until the cold air mass descending the mountainous region dissipates. The katabatic flows may also be stopped or dispelled by the presence of a countervailing push from the ice shelf emanating from the side of the mountains. The regular storms exhibit short-lived frontal systems, but the katabatic flows last for days (Doodge, 2010).
Katabatic winds or flows can also be defined as the downslope wind that is generated by surface cooling effects of mountain meteorology. The katabatic flows usually occur near a surface in a stably stratified atmospheric boundary layer and exhibit a maximum range from a few meters to a few hundreds of meters. The katabatic winds are observed at the same latitude of the globe as soon as a course of cooled air meets a significant slope. An interesting fact is that the katabatic winds in Antarctica are the strongest compared to others experienced across the world (Kouznetsov, 2012). The shape of the land in Antarctica contributes to the strength of the katabatic winds in the region. The Antarctica katabatic winds occur when the cold, dense air at the peak of ice sheets flows down the coastal slopes under the effect and influence of gravity forces. Antarctica is known for producing the strongest and the most lasting or enduring katabatic flows since it is the highest and the coldest continent in the world (Brockett, 2005).
There exist various factors contributing to the origin of katabatic flows in Antarctica. The radiative cooling immensely adds to the appearance of the katabatic winds in Antarctica. Antarctica can be defined as a dome of ice that has a plateau of about 400m high in its interior that slopes towards its perimeter at sea level (Doodge, 2010). The Antarctica's nature as the coldest place on earth is attributed to the fact that any warming radiation received from the sun is reflected back into space by the enormous ice and snow coverage. The high reflectivity of snow in Antarctica causes the air layer near the surface to be cooled for most time of the year. Since the lower layers of the atmosphere in Antarctica seem to be in direct contact with the ice cap, the atmospheric air becomes cold and the colder the air, the denser it becomes, which eventually accelerates the katabatic flows.
Thermal inversion illustrates how the air near the ground is cooled while the air in the upper atmosphere is warmed. The high and persistent inversion conditions develop in Antarctica at around an altitude of 1000 meters to find air much warmer than at ground level that goes as much as 30 degrees (Brockett, 2005). Thermal inversion and radiative cooling cause the surface layer of air to have a lower temperature than the free air at a downslope of the ice cap at the same altitude, thus initiating gravitational air movement down the slopes (Brockett, 2005). The masses of the cold air, katabatic winds, contract and become heavier than the previous masses as they start to move down the slope under the effect of the inclining ice cap. The katabatic winds of Antarctica vary depending on the location, but they are stronger in the coastal regions of Antarctica.
Antarctica is recognized across the globe as the windiest place on the planet earth. There exist different katabatic winds that blow across Antarctica that vary from the inversion winds at the South Pole to the winds that are funneled between the islands covering the coastal region. The other extreme category of the wind in Antarctica includes the violent katabatic blizzards that exhibit potential to develop with incredible speed (McGonigal, 2001). The inversion winds contribute to the formation and maintenance of katabatic winds, and the inversion winds result from the gravitational forcing of the cold air masses on an inclined terrain. The steeper the slope of the ground, the more the flow of the cold air masses, and the stable air masses described as inversion winds become purely driven by gravitational force and friction-retarded wind existing in the boundary layer. Data collected and observation made on the wind at auxiliary meteorological stations suggest that on steeper slopes, the winds take characteristics of the purely-driven flow.
The other category of katabatic winds includes the prevailing katabatic winds. Unlike the inversion winds, the ordinary katabatic winds are characterized by a high variability of wind speed that does not usually assume a steady state. Meteorological stations report that the ordinary katabatic winds show tendencies of high rates that alternate irregularly with periods of weak winds or calms (Renfrew, 2006). The ordinary katabatic winds are noticed near the coastal regions of East Antarctica. Researchers attribute the discontinuity in the flow of the ordinary katabatic winds to the typography of Antarctica's upwind terrain. The persistence of the regular katabatic wind flows requires the convergence of the cold air currents that are strengthened by a drainage area of sufficient size and inclination (Hay, 2004).
The last category of the Antarctica katabatic flows includes the massive katabatic winds. The massive katabatic winds blow continuously for days or several weeks at extreme speeds. The determining factors in the strengths of the heavy katabatic winds include three facets. The topography of Antarctica exhibits an upwind terrain that contributes to the convergence field of motion formation and persistence. The Antarctica plateau forms a large size of the drainage area ideal for the formation of the heavy katabatic winds (Shapiro, 2008). The strong radiative cooling in the Antarctica region immensely contributes to the formation of the great katabatic winds since radiative cooling provides the efficient production of a cold boundary layer air. Most of the coastal regions of Antarctica show smaller drainage areas on a plateau with more divergence than convergence characteristics, which consequently makes Antarctica experience heavy katabatic winds (Brockett, 2005).
The ferocious winds defining the Antarctica continent ruin the reputation of the region since it is deemed as the most inhospitable continent on planet earth. The local blizzards brought about as a result of the strong katabatic winds show the life-threatening wind-chill temperatures that pose a danger to those willing to visit the Antarctica region (Renfrew, 2006). The traveling and various outdoor activities are therefore practically impossible during the winter season in Antarctica as a consequent of the extraordinary katabatic winds.
The visibility in Antarctica becomes considerably hampered by the presence of the strong katabatic winds. The cold dense air experienced along the coastal areas of Antarctica that flow down the ice-cap funnels through the topographic channels at extremely high speeds lift snow off the ground thus reducing visibility to a few feet high (Renfrew, 2006). The wind-chill factor is a phenomenon that shows that when the wind increases, the rate at which the body loses heat becomes increased too. The wind-chill factor measures the cooling effect of the wind, and this affects the normal functioning of the body.
Travelers on expeditionary missions in Antarctica experience drastic weather changes that at times terminate the mission. Travelers to Antarctica describe the area as notorious for wind caused by the large Antarctic ice cap that contributes to the formation of katabatic winds. The strong katabatic flows occur on long glaciers in high latitude areas, and such areas experience the Coriolis effect that deflects the flow of air, thus affecting the turbulent transports in the boundary layer (Renfrew, 2006).
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The strong katabatic winds in Antarctica play a vital role in the development of the Antarctic bottom water. The Antarctic bottom water is usually cold and dense and slowly sinks to the profound depths of the ocean that brings oxygen with it. The phenomenon occurs when the katabatic winds push away the sea ice and cool the exposed ice until there is a formation of new ice. This formation leaves behind most of the salt in the ice, thus making the water below the ice the saltiest and the densest in the ocean. The Antarctic bottom water, usually cold, carries nutrients and oxygen with it that supports sea life for thousands of kilometers away from the sea (McGonigal, 2001).
Several general features of the katabatic flows in Antarctica become noticed from observed stations and research findings as discussed in the above paragraphs. The behavior of the katabatic winds in the eastern Antarctica, as well as the uphill direction tendencies, shows that they can be attributed to the Coriolis force and density of air. The radiative cooling, gravitational force, and inversion cause to katabatic winds and determine the strength of the winds, creating the ordinary katabatic winds and heavy katabatic winds. The effects of the katabatic winds in Antarctica affect expeditionary missions since they reduce visibility and destabilize the tents made for temporary staying purposes.
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