China used cloud seeding to trigger rainfall that would clear up air pollution in Beijing ahead of a major political event in July — the 100th anniversary of the Chinese Communist Party, the South China Morning Post reported.

According to the news outlet, scientists at Tsinghua University said the government laced clouds with chemicals to bring on rainfall over suburban Beijing and some neighboring areas hours before the July 1 centenary event.

In a research paper, the scientists estimated the artificial rain reduced the level of the air pollutant by more than two-thirds, and improved air quality from "moderate" to "good" under the World Health Organization standards, the news outlet reported.

The team, led by Wang Can, an environmental science professor, said it was unlikely the drop in pollution was natural occurring since "artificial rain was the only disruptive event in this period," the news outlet reported.

Their research was published in "Environmental Science," a peer-reviewed Chinese journal, on Nov. 26.

Tens of thousands of people attended the July 1 event in Tiananmen Square that began with overcast conditions, the South China Morning Post reported. And there was a downpour soon after the two-hour ceremony ended.

According to the news outlet, China’s weather authorities have been trying to alter the weather for important events since 2008, when Beijing hosted the Olympic Games. But according to the Tsinghua scientists, the party centenary presented unprecedented challenges.

One of them was an unexpected increase in air pollutants in the lead-up to the anniversary, the scientists said. While most industrial activities like factories and cargo trucks had been halted in Beijing and nearby provinces, air circulation had also slowed, making it harder for pollutants to dissipate, the news outlet reported.

Beijing also recorded its wettest summer on record this year, with almost twice the average amount of rainfall.

In the week before the July ceremony, it rained nearly every day, and on the day of the event, people at the event were given raincoats as part of a souvenir pack. According to the news outlet, a two-hour cloud-seeding operation began the night before.

According to The Hill, China announced last week it would be developing a weather modification system by 2025 that would produce artificial rainfall over 224,000 square miles. 

Cloud seeding has been around since the 1940s, and more than 50 countries around the world have tried it, but as climate change has worsened in recent years the practice has taken on renewed popularity, The Hill noted, adding states like Idaho, Wyoming, and Oregon have found success in cloud seeding.

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