What is polar vortex?
The polar vortex is a Geographical phenomenon in which a large area surrounding both the poles of the Earth experiences low pressure and cold air. It mostly exists close to the poles, but its location and intensity vary from time to time. The polar Vortex becomes strong in winter and weakens during summer. Each polar vortex is a persistent, large-scale, low-pressure zone less than 1,000 kilometers in diameter, the direction of rotation is counter-clockwise at the North Pole. The term ‘vortex’ refers to the counter-clockwise flow of air that helps keep the colder air near the Poles. The bases of the two polar vortices on which it depends are located in the middle and upper troposphere and extend into the stratosphere. Polar Vortex impacts the movement of Jet Stream which further causes change in the climate of the affected region. Due to the wavy nature, Polar Vortex Jet stream becomes rotary in nature which is generally a straight one.
The polar vortex is mainly of two types on the basis of intensity and process of formation;
1. Strong Polar Vortex
2. Weak Polar Vortex
Strong Polar Vortex:
Strong Polar vortex is the more common type of polar vortex. When the polar vortex is strong, this creates strong low pressure in the Arctic region, and the temperature of this region also so low. Because of the pressure difference between the north pole and mid-latitudes, air flows into the low-pressure i.e.arctic region, and this confines the cold air to high latitudes closer to the Arctic. Therefore it is often mild across the Eastern US, Europe, and East Asia during winters, and also the temperature is very low when the polar vortex is strong. During a strong polar vortex, due to high-pressure gradient airflow fast and in the west to east direction.
Weak Polar Vortex:
When the polar vortex is weak, the flow of air is weaker and meanders north and south (rather than west to east which is a strong Polar vortex). This allows a redistribution of air masses where cold air from the Arctic spills into the mid-latitudes and warm air from the subtropics is carried into the Arctic. This mixing of air masses resulted into s Global climate change which favors more storms and snow in the mid-latitudes. During a weak polar vortex, high pressure occurs in the Arctic region and is referred to as the negative phase of the Arctic Oscillation (i.e. Circulation of wind in the counterclockwise direction around 55-degree latitude). The north to south direction of the polar vortex carries cold Arctic air into the mid-latitudes of Eastern US, Europe, and East Asia which resulted in cold across the Eastern US, Europe, and East Asia.
Impact of Polar Vortex on Global and Indian climate:
1. Polar vortex impact on jet stream:
- Many times during winter in the northern hemisphere, the polar vortex will expand its area to lower latitude by sending cold air southward with the jet stream.
- Reduction in snow cover and less reflection of sunlight by sea ice resulted in an increase in temperature which further increased evaporation and transpiration, which in turn alters the polar vortex’s pressure and temperature gradient, causing this phenomenon to weak.
- This becomes apparent when the amplitude and direction of the jet stream increase across the northern hemisphere, causing the Jet stream to spread further south or north, which resulted in the transfer of cold air from pole to low latitude and warm air from low to high latitude.
- This amplitude of the jet stream increases with a weaker polar vortex, thus resulted in the change in the climate. A blocking event in 2012 emerged when a high-pressure over Greenland steered Hurricane Sandy into the northern Mid-Atlantic States due to the movement of Jet stream.
- If this jet stream’s circulation is strong, the polar vortex phenomenon resulted in a circular shape near to pole.
- Change in the circulation of the polar-front jet stream resulted in incursions of energy generated due to land-ocean contrasts in temperature and air deflected by large mountain ranges into the path of the jet stream which flows in the stratosphere.
- Disturbances in the jet stream and the intrusion of warmer air in cold air areas (Arctic Circle) will force colder air of the polar region to lower latitude.
- Interaction of Jet stream with the polar vortex resulted in polar temperature further south.
2. Polar vortex and cold climatic conditions:
- Recently, it brought cold wave-type conditions in Midwest US.
- The phenomenon mostly become popular among Americans during a particularly frigid spell in 2014, when the first-time word “polar vortex” is used. It was also a major cause factor in the “bomb cyclone” that severely impacted the east coast of the US.
- Studies have shown a recent frequent rise in cases where the polar vortex has moved into heavily populated areas. It resulted in research about causing factors and some scientists make climate change responsible for it.
- The polar vortex is a well-documented, stationary pattern but some scientists say climate change impacts its stability which resulted in a change in climate from the normal range.
- Mostly the weather is cold across the Eastern USA, Europe, and East Asia during winters when the polar vortex is weak through the jet stream.
3. Polar vortex and drop in average temperature in winters in India:
Over the past few decades, the hill states of north India have experienced unusual cold which is not as per prescribed climate, it is indirectly caused by the Polar Vortex.
Since it is known that arctic cold air blast bottled by the polar jet stream but sudden stratospheric warming events, intense pacific cyclone and blocking lead to the expansion of the vortex and consequently it increases the frequency and Intensity of cold weather.
Due to the breakdown of the polar jet stream, It expands the arctic cold air blast which directly affects the global weather system, and the country of west Asia along the Himalayan belt like India is facing the high frequency and intensity of Western that resulted in an increase in temperature and rainfall. This can be Considered as Polar Vortex’s indirect effect.
The change in the climate of India’s hilly states does not directly affect of the polar vortex, but cause-effect of weakening of the Western mid-latitude due to the breakdown of the polar jet stream which resulted in the Southwest shift of Western Disturbance causing above-normal snowfall and precipitation over northern India along Ganga valley.
The IMD has also clarified that increased penetration of cold waves and cold days towards the southern peninsula (till Telangana) also has also a strong cause-effect correlation with the Movement of the Arctic Polar Vortex.
And the frequent western disturbances in the Himalayan region are resulted in prolonged winters at regular intervals compared to the previous winter pattern.
Hence, Polar Vortex impacted severely not only to Indian continent but also the global climate. The main cause behind the Polar vortex is Global warming and others are need to find out. Due to the importance of the Polar Vortex for Global climate stability, there is a need to address Global Warming and more research on other cause and their remedial measure.
This article is written by;
Selected as Assistant Commandant (UPSC CAPF 2019)
Also appeared for Civil Services Interview
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