Is air pollution making Northeast Asian storms more powerful?

January 22, 2014
Stormy weather in Northeast Asia

Extreme air pollution in Asia is affecting weather and climate patterns, according to a new study. Using climate models and data collected about aerosols and meteorology data from the last 30 years, the researchers found that air pollution over Asia – much of it coming from China – is impacting global air circulations.

Winter cyclones in northwestern latitudes including China, Korea and Japan have packed stronger winds and more rain as a result of rising levels of particulate pollution, they said. Conditions tend to worsen during winter months when a combination of stagnant weather patterns mixed with increased coal burning in many Asian cities can create pollution and smog that can last for weeks.

“The models clearly show that pollution originating from Asia has an impact on the upper atmosphere and it appears to make such storms or cyclones even stronger.  This pollution affects cloud formations, precipitation, storm intensity and other factors and eventually impacts climate,” said Renyi Zhang, an atmospheric scientist at Texas A&M University and co-author of the paper, published in the journal Nature Communications.

The scientists drew up a computer model to simulate aerosol pollution flowing downwind from East Asia to a cyclonic breeding ground east of Japan in January and February, a zone lying north of 30 degrees latitude.

They found a good match with two decades of satellite data: 1979-1988; and 2002-2011, when Asian growth really hit its stride, especially in China. In the latter period, there was a clear rise in cyclone intensity but no change in frequency of storms or location.

According to Yuan Wang, a co-author from California Institute of Technology’s Jet Propulsion Laboratory, dusty fallout, known as aerosols, affects how moisture develops in clouds and how heat is distributed in storm systems.

He said aerosols accelerate the formation of droplets because they provide a nucleus on which water vapor condenses. Clouds influenced by aerosols carry as much as four times more droplets, leading to a roughly seven-percent increase in rainfall across the region, it found.

The aerosols are also likelier to encourage the formation of brighter high-altitude cirrus or "anvil" clouds, which help to warm the sea surface, thus providing heat to fuel cyclones. The additional warming effect can be as much as 11 percent, according to the research team.

They point out, however, that research into the effect of aerosols on clouds has returned highly variable findings and is considered to be one of the biggest areas of uncertainty in climate science.

That said, co-author R. Saravanan from Texas A&M says the models used by the team and the data are very consistent with the results reached. “Huge amounts of aerosols from Asia go as high as six miles up in the atmosphere and these have an unmistakable impact on cloud formations and weather.”

Looking ahead, Texas A&M’s Zhang said that future research is needed into exactly how aerosols are transported globally and impact climate. “There are many other atmospheric observations and models we need to look at to see how this entire process works,” he said.