The monsoon rainfall over India is famously influenced by El Nino and La Nina events, the alternating warming and cooling of the East Pacific ocean that impacts weather worldwide. A recent study, which was conducted by Indian researchers from the National Institute of Advanced Studies in Bengaluru and the Indian Institute of Tropical Meteorology in Pune, has unveiled a new dimension to this influence. They discovered that these two weather events also influenced the air quality in our country.
The study, which examined the winter of 2022, suggests that the unusual air quality in some Indian cities during that period could be attributed to the record-breaking spell of La Nina. This is the first time air quality in Indian cities has been linked to a La Nina event, indirectly connecting it to climate change, which is intensifying the impacts of El Nino and La Nina.
A Synopsis of the Study
During the 2022–23 winters, a strange shift in pollution levels was experienced in India. The air quality in a number of Indian cities was strangely altered. There was poor air quality in the regions of south-western India, which was very unusual. This air consisted of high levels of pollutants, which, in turn, degraded atmospheric conditions. These inconsistencies in the air quality were attributed to the prevalent La Nina conditions at that time by the researchers after thoroughly analysing the meteorological data and the measurements of air quality. However, northern India experienced comparatively cleaner air, which contrasted typical patterns.
According to the scientists, both El Nino and La Nina severely impact the weather patterns across the globe, including the monsoon rainfall in India.
The La Nina event is also related to the inconsistent air quality in select cities of India during the winters of 2022. In the study, the wide-ranging consequences of climate change are brought to light. Scientists are of the opinion that both El Nino and La Nina are strengthened by climate change. As a result, their impact on local weather and environmental conditions increases.
Factors responsible for change in the air quality
- Shift in wind direction Under normal conditions during winter, winds move from Punjab towards Delhi and further towards the Gangetic Plains. These winds often carry pollutants resulting from the burning of stubble. However, during the 2022 winters, the direction of wind circulation was considerably altered. The direction of winds that blow from northwest India was shifted towards the south direction owing to the extended impact of La Nina.
- Inconsistent behaviour Due to this change in the wind direction, the winds full of pollutants blowing from Punjab and Haryana bypassed Delhi NCR and moved towards Western and Southern India. As a result, the PM2.5 levels rose in the southern cities, such as Mumbai, Chennai and Bengaluru, and degraded their air quality. Notably, Delhi NCR experienced relatively lesser pollution during this time.
- Pollution and winter months in India During winter months, i.e. from October to January, cities in North India, such as Delhi, experience high levels of PM2.5. This happens because of a number of meteorological factors and transfer of pollutants from two states—Punjab and Haryana. South and West India experience less pollution during the winter months due to their proximity to the oceans. However, during the 2022 winter, the situation was completely opposite.
- La Nina effect prolonged As there has been triple dip La Nina, its impact on wind patterns has been aggravated. Consequently, the distribution of air quality all over India has been drastically changed.
Triple dip La Nina refers to the prolonged La Nina that continued for three consecutive years by the 2022 winter. It was an uncommon and extended La Nina event that affected weather patterns all over the globe. This phenomenon is also known as a rare ‘Triple Dip’ phenomenon.
- More exploration required According to the study, wind patterns have been altered owing to La Nina. Besides, air quality of different places has also been changed. However, it is still uncertain if air quality will be affected by El Nino too. Thus, researchers are required to carry out further exploration in this regard.
Understanding La Nina, El Nino, and ENSO
La Nina Also known as ‘El Viejo’ or ‘cold event’, La Nina is a weather phenomenon wherein a band of cooler water moves from east to west in the equatorial Pacific Ocean. It usually occurs during the months of April, May, and June but is strengthened between October and February. This event typically continues for 9–12 months but can continue for two years. It occurs every two to seven years.
El Nino is also an oceanic and atmospheric phenomenon wherein a band of warmer water moves from west to east in the Equatorial Pacific Ocean. It also occurs during the same months as La Nina and continues for a similar period of time. However, it occurs more frequently compared to La Nina.
El Nino literally means ‘a little boy’ in Spanish; while La Nina literally means ‘a girl’ in Spanish. But these names do not refer to humans. El Nino originated in the late 1800s. During that time, some fishermen on the Peruvian coast noticed that the waters were warmer than usual during some years, particularly in December. As this event happened around Christmas, they named it as ‘El Nino’ which means ‘a Christ child’.
Both El Nino and La Nina are contrasting events that considerably affect the global weather conditions, wildfires, economics, and ecosystems, as these are deflections from the normal surface temperatures. So, these events are considered important climatic phenomena on the earth.
ENSO La Nina and El Nino together form a cyclical process known as El Nino Southern Oscillation (ENSO). They are basically contrary phases of this process, with La Nina being the cold phase and El Nino being the warm phase. Either of them occurs at a time. However, when neither La Nina nor El Nino occurs, it is known as the neutral phase. All these phases are a part of the ENSO.
Thus, ENSO refers to a climatic pattern in which the temperature of the waters of the eastern and central tropical Pacific Ocean, the sea level pressure, the pattern of upper-and lower-level winds and the amount of tropical rainfall across the Pacific Basin keep changing. This process occurs repeatedly.
Impact on India’s climate Normally, trade winds blow from east to west along the equator and thus regulate the direction of ocean currents in the Pacific Ocean. As a result, warm water flows from South America towards Australia. The warm water near Australia is known as Western Pacific Pool (WPP). The temperature is higher, while the atmospheric pressure is lower over Australia and Southeast Asia. The moisture-laden winds move from the WPP towards Southeast Asia, which bring monsoons in India. Besides, cold Peruvian current flows from the depths of the ocean towards South America, thereby creating high pressure over Peru and Ecuador. So, no rainfall occurs in these regions.
These normal conditions are disrupted by El Nino and La Nina, the two contrasting climatic phenomena.
Owing to El Nino phenomenon, the trade winds as well as Peruvian currents get weakened. As the speed of trade winds reduces or their direction is reversed, Peruvian currents become warm. Thus, low pressure is created over South America. As the temperature is high here, the moisture-laden winds flow towards Peru from the Western Pacific Pool. Additionally, a high pressure is created over Australia and Mascarene Islands, which otherwise push moisture-laden winds towards India. So, the Peruvian coast receives heavy rainfall; whereas, there occurs drought-like conditions in Australia as well as India. Indian monsoons are likely to be adversely affected due to such conditions, thereby impacting agriculture in India.
At the time of La Nina, the Western Pacific Pool becomes warmer than usual, which increases the temperature of that area. So, the atmospheric pressure becomes lower in this region. This results in stronger monsoon winds over Australia as well as India, which brings more rainfall to both these regions. Sometimes, it causes severe floods in Australia. However, there is no rain in South America, resulting in drought-like conditions there, particularly in Peru and Ecuador. This also leads to stronger trade winds and colder Peruvian currents.
Conclusion
The findings of the study are important for several entities, including environmental agencies, policymakers, and public health authorities, whose main objective is to lessen the harmful effects of air pollution in India. If the stakeholders understood the impact of La Nina on air quality, they would be in a better position to deal with inconsistencies in atmospheric conditions. Consequently, they would put more efforts so that public health can be maintained and environment can be conserved.
Besides, as per the study, the global climatic phenomena and local environmental dynamics are connected to each other. The weather patterns are continually altered and extreme events have been worsened due to climate change. It is extremely important to comprehend these complex interactions so that varied challenges that occur owing to environmental degradation and climate variability can be tackled.
Further, in order to understand the interconnection between La Nina and air quality in India more comprehensively, greater research work and additional monitoring work is the need of the hour. The complicated mechanisms with which atmospheric processes are driven can be unveiled by the scientists with the help of novel modelling techniques and thorough data analysis. In addition to these, systematic capabilities to assess environmental risks can be improved upon by the scientists.
Finally, the study suggests that a holistic approach is vital to facilitate climate resilience and environmental stewardship. A collective effort is required at all levels, i.e., local, national, and international levels to deal with the consequences of climate change for the welfare of communities around the world. The study also highlights the importance of continuous scientific research in the field of climate change, particularly, the interaction between global weather events such as La Nina and air quality dynamics in India along with regional environmental conditions. These complex relationships must be understood so that appropriate policies can be implemented to deal with the challenges posed by the climate change.
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