Amid the deteriorating air quality in the national capital, the AAP government has long been considering a proposal to bring respite to Delhiites amid 'severe plus' AQI levels—artificial rain.


Delhi Environment Minister Gopal Rai said he has written to Union Environment Minister Bhupender Yadav four times over the past few days, seeking urgent clearances for cloud seeding to artificially induce rain that could combat the escalating pollution crisis in the city. 


Delhi has been shrouded in a thick grey haze for the third consecutive day as of Tuesday, with pollution levels remaining alarmingly high at 488 in the 'severe plus' category.


ALSO READ | Delhi Govt Seeks Centre's Nod For Artificial Rain Amid Severe Plus AQI


Despite emergency measures under GRAP-IV in place, the pollution levels remain unabated, the Delhi government has been calling for immediate intervention from the central government. 


But what are artificial rains and how does cloud seeding work? Here's everything you need to know:


What Is Artificial Rain?


Artificial rain, which is also interchangeably used with cloud seeding, is a method of weather modification that uses artificial rain chemicals to induce or increase rainfall.  


In order to create rainfall, chemicals are dispersed on clouds, which induce freezing nucleation. The ice crystals formed as a result of the process are too heavy and fall from the clouds and melt to form water droplets causing artificial rain. 


Cloud seeding is used for many purposes, including enhancing rain, augmenting snowfall, dispersing fog and mitigating hail damage. 


Science Behind Artificial Rain


In order to understand the science behind artificial rain, let’s first take a look at how normal rain occurs.


When water from the rivers, seas, oceans and other water bodies evaporate, they rise up and the water vapour condenses into water droplets or ice crystals at higher altitudes. These water droplets or ice crystals aggregate to form clouds. 


The water vapour cools and condenses around dust particles or salt floating in the atmosphere. The dust or salt particles are known as condensation nuclei and without them raindrops or snowflakes cannot form and precipitation cannot occur. When the droplets in the cloud gets too heavy, they fall to the ground as rain or precipitation.


However, in the case of artificial rain or cloud seeding, tiny condensation nuclei or ice nuclei are introduced into subfreezing clouds to improve the clouds’ ability to produce rain or snow. These chemical particles serve as nuclei for water droplets to form around, potentially resulting in artificial rain. The nuclei serve as a base for raindrops or snowflakes to form. 


During the cloud seeding, chemicals like silver iodide, potassium iodide and dry ice are sent to the atmosphere through aircraft or helicopters.


Generally, there are two ways to implement cloud seeding, firstly, by seeding supercooled clouds with silver iodide or dry ice, causing ice crystals to grow and consume moisture from the cloud to start rainfall. 


The second process involves warm clouds and hygroscopic materials like salt particles, which take on water vapour, becoming bigger to fall faster.


Is The Concept Of Artificial Rain New?


Delhi's artificial rain solution to the AQI problem is not new. Last year, when the AQI exceeded 400, Delhi Environment Minister Gopal Rai said the government is planning to induce artificial rain through cloud seeding. 


Rai held a meeting with scientists from IIT-Kanpur with a proposal for artificial rain around November 20-21 last year, with the government seeking the Supreme Court’s approval and the Centre’s assistance. 


IIT-Kanpur scientists had presented cloud seeding and artificial rain as pollution reduction steps. IIT-Kanpur had emphasised the need for at least 40 per cent cloud cover for cloud seeding, with potential favorable conditions on November 20-21. 


Cloud seeding has been used by the United Arab Emirates government to tackle water scarcity challenges in the country.