High above mountains of Nepal, detectors study impact of Asian monsoon on climate

As rain sheeted down on the roof of an airplane hangar in the mountains of Nepal, a group of researchers watched a small, strangely shaped airplane disappear into the clouds. The plane, laden with custom-built detectors and instruments, was headed for the top of the most powerful, organized weather system in the world: the monsoon over southeast Asia.

“We all had our hearts in our mouths,” said Assoc. Prof. Liz Moyer, a University of Chicago geophysical scientist who studies the atmosphere and the effects of climate change.

The mission had been scheduled with an ambitious goal: to better understand the monsoon structure and its role in the global climate. More than one such mission had already been canceled for weather, customs, regulations or other difficulties. But this one, held together with the hopes of more than 50 scientists, was headed for a different fate.

Accompanied by UChicago graduate and undergraduate students, Moyer was part of a July 2017 international collaboration funded by the European Commission to send a plane over the monsoon for the first time. Their results, which will be discussed this week at a meeting in Italy for the science teams in the project, reveal new details about how pollution and water from near the ground is transported to the stratosphere during the monsoon.

Their questions: How high do the clouds of the monsoon reach? Are they boiling up over into the stratosphere—the second major layer of the Earth’s atmosphere? And to what extent do they carry surface pollution high enough to contribute to ozone destruction? “These seem like simple questions, but no one had ever been to the top of the monsoon before,” Moyer said.

Clouded with mystery

The Asian monsoon is the most massive weather event on the planet, and even apart from the treacherous winds and temperature shifts across altitudes, it makes its own chaos on the ground.

Even getting equipment in had been a struggle for the scientists: They had shipped some of the equipment overseas to India, but trucks struggled to cross flooded roads on the way to Nepal. By go time, not everything had made it—they had to push the plane in and out of the hangar by hand, because that equipment was stalled—but the crucial parts were all there, and they could “MacGyver” the rest of it, Moyer said.

Despite the challenges, the scientists felt the chance for knowledge was too important to pass up. Their work would not only help better understand the monsoon, which affects the livelihoods of billions of people, but also the climate for the entire planet.

“By far the biggest uncertainty in our global climate models today is clouds,” said Moyer. Much of this uncertainty is about lower clouds, but we also don’t know as much as we’d like about cloud formation at the highest altitudes and over the tropics, where the plane was headed. And it’s difficult to study, because clouds at such altitudes are often made up of ice particles invisible to the naked eye. But they may deeply affect the global climate, including storms, the ozone layer and how much heat is reflected from Earth.

Other scientists on the collaboration were studying whether particles from the lower layers of the atmosphere were being pulled up by the powerful winds of the monsoon. If so, pollution from the ground could be traveling into the upper atmosphere, which would affect cloud formation. Moyer’s lab, on the other hand, was tracking water on its journey to the stratosphere.

That led them to the hangar in Nepal. Borrowing a crane, they lifted the 330-pound detector, built over three years in Moyer’s lab, onto the plane. “That was probably the most terrifying two minutes of my life,” said undergraduate Clare Singer, a fourth-year who traveled with Moyer for the mission.

The plane, a Russian-made Myasishchev M-55 Geophysica, is one of just a few in the world suited to fly at that altitude: 65,000 feet into the atmosphere.

After its four-and-a-half-hour trip, the plane finally came back into view. It landed, its Russian pilot unconcerned by the perilous trip. The scientists, less unruffled, rushed to download the data.

‘We could see it immediately’

Even without analysis, Moyer said they took one look and immediately knew their first question had been answered.

Their detector was looking for the isotopic makeup of water in the highest altitudes. Certain heavier isotopes would mark water as having recently come from the ocean, pulled up as ice by the powerful forces of the storm. Those signatures were all over the readings.

“We could see it immediately. There was just abundant evidence that the lid of the troposphere had been punctured,” she said. “What remains to be seen is how that influences the highest reaches, closest to the ozone layer. These are the questions we’ll tackle at the meeting in May.”

Buoyed by the results, Moyer recently received a five-year, $5 million National Science Foundation grant to study high-altitude sub-visible cirrus clouds. In conjunction with Princeton, Harvard and the University of Washington, her group will work to better model the formation and evolution of these thin ice clouds in the uppermost reaches of the troposphere, to understand how they may change in the future.

“I am concerned, though,” Moyer said. “Now the students might think you can do one run and always have new science come pouring right out the first time.”