Above: Arunima Prakash
Header Image: A lidar beam shooting into the night sky from Xinzhao Chu's lab in Antarctica.

Arunima Prakash is preparing to study the upper atmosphere from one of the coldest and most desolate places on Earth: Antarctica.

Prakash, an aerospace PhD student at the University of ŷ���ڱ���Ƶ Boulder, is studying polar mesospheric clouds and their relation to the solar cycle and polar vortex effects.

“There has been a long debate about how the solar cycle affects these clouds,” Prakash said. “Past satellite observations say the sun had a dominant effect, but we’re not seeing that correlation anymore. We want to study why. It could be a long-term indicator of climate change.”

Prakash is part of a team working under Xinzhao Chu, a professor in the Ann and H.J. Smead Department of Aerospace Engineering Sciences at ŷ���ڱ���Ƶ Boulder. Chu has a dedicated facility located at McMurdo Station, Antarctica. There, she uses specialized lidar systems that shoot pulsed laser beams into the sky to observe conditions from roughly 10-200 km (6-124 miles) in altitude, where terrestrial weather and space weather processes influence each other.

The frozen tundra of Antarctica may seem an unlikely place to conduct complex space-atmospheric research, but the unique atmospheric conditions available only at extreme latitudes make the location perfect for these studies.

Prakash’s work was recognized at the 2022 International Laser Radar Conference for and earned at the Coupling, Energetics and Dynamics of Atmospheric Regions Program workshop in June.

Her work thus far has only been through complex analyses of already collected data. So she is eager to get to Antarctica to do her own hands-on research.

She is part of a team that will depart from Boulder for Antarctica within the next few weeks. Although Chu’s lab is well established at McMurdo, the facility has sat unused for the last two years due to the COVID-19 pandemic.

Prakash said the team is uncertain what they will find once they are on site.

“We are preparing for the worst,” Prakash said. “You generally want lasers to be continuously running, but these have been off for two years. We don’t know what kind of problems we’ll face and are gathering all sorts of extra parts to bring.”

Although it would be ideal if everything works fine, Prakash is also excited about the potential for diagnosing and solving electronics problems.

“For my degree, I didn’t want to be in one hole doing just one thing,” she said. “With Dr. Chu, I have the chance to work on science and engineering. We do a lot of electronics, lasers, photonics, optics, and data analysis. It’s a very good chance to learn more and keep in touch with what I know.”

Prakash plans to stay at the lab in Antarctica for six months. Once the equipment there is up and running, she will have near uninterrupted opportunities to conduct her research.

“Being in Antarctica I will have absolutely no distractions in terms of productivity,” Prakash said. “I’m looking forward to it as much as I’m looking forward to seeing the auroras, and the stars, and improving these atmospheric models.”

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It is one of the coldest and most isolated places on Earth, but for a team of scientists and engineers from ŷ���ڱ���Ƶ Boulder, it is the ideal location to conduct complex space-atmospheric research: the frozen tundra of Antarctica.

Xinzhao Chu has earned a $3.3 million, five-year to study complex interactions between the Sun and Earth’s upper atmosphere that impact our climate, life on Earth, and orbiting satellites. The research utilizes advanced lidar systems and is conducted primarily from McMurdo Station, Antarctica.

Chu is a professor in the Ann and H.J. Smead Department of Aerospace Engineering Sciences and a fellow in the ŷ���ڱ���Ƶ Boulder

“By more fully understanding the Sun-Earth interactions, we can understand space weather better to guide spacecraft to avoid problems from solar storms, we can improve upper atmosphere climate models and better predict climate change,” Chu said.

Lidar research has been a cornerstone of Chu’s career, with a focus in Antarctica. Unique atmospheric conditions available only at extreme latitudes make the location perfect for these studies. Her specialized lidar systems shoot pulsed laser beams into the sky to observe conditions ranging from roughly 10-200 km (6-124 miles) in altitude, where terrestrial weather and space weather processes influence each other.

This NSF award marks her fourth to conduct studies from Antarctica. By this grant’s end, she will have conducted research for more than a full solar cycle, which lasts 11 years.

“The sun is coming out of solar minimum and will begin to ramp up to solar max,” Chu said. “During that time we’ll see much more activity in the ionosphere and solarsphere. With these long-term measurements, we can confirm long-term trends.”

Chu has a dedicated facility at near McMurdo Station from her previous grants, but it has been inaccessible for the last 12 months due to the ongoing COVID-19 pandemic.

“It will be nearly two years of a gap before we’re using the laser again,” Chu said.

During the time her team has been away from McMurdo, they have been analyzing earlier data and preparing for a new deployment. Her past research has netted dozens of published papers, including a discovery last year of a critical connections between wind patterns at the equator and atmospheric waves 6,000 miles away in Antarctica.

“It’s challenging to get this data, but once we get it the science pays off,” Chu said.

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Twice a day, at dusk and just before dawn, a faint layer of sodium and other metals begins sinking down through the atmosphere, about 90 miles high above the city of Boulder, ŷ���ڱ���Ƶ. The movement was captured by one of the world’s most sensitive “lidar” instruments and reported Tuesday in the AGU journal . 

The metals in those layers come originally from meteoroids blasting into Earth’s atmosphere, which bring an unknown amount of material to earth; and the regularly appearing layers promise to help researchers understand better how earth’s atmosphere interacts with space, ultimately supporting life.

“This is an important discovery because we have never seen these dusk/dawn features before, and because these metal layers affect many things. The metals can fall into the ocean and act as fertilizer for ecosystems, the ionized metals can affect GPS radio signals….” said Xinzhao Chu, CIRES Fellow, ŷ���ڱ���Ƶ Boulder professor of Aerospace Engineering Sciences, and lead author of the new assessment. 

It is the first time that the metal layers have been seen so regularly at these extreme heights in the atmosphere. Such high-altitude metal layers were by Chu’s group just 10 years ago above McMurdo, , but there they occur more sporadically. Above Boulder, they’re consistent, daily, and synched with high-atmospheric “tidal winds” created by the sun’s periodic appearance. To understand those winds, the research team relied on data from satellite.    

“This work was the very first use of the ICON tidal wind product. The product allowed Xinzhao’s team to calculate the flow of metal ions over Boulder. It’s a great example of how these tides seem to affect everything in space near Earth,” said Thomas Immel, Principal Investigator of the ICON Mission and a physicist at UC Berkeley's Space Sciences Laboratory.

“Consistent daily patterns seen in our Boulder observations tell us that there are unknown processes at play, a golden opportunity for atmospheric scientists to discover new phenomena and mechanisms,” said Jackson Jandreau who worked alongside Chu and Yingfei Chen in this study. Chen and Jandreau are both PhD students in . 

The discovery also gives researchers a window into a crucial part of the atmosphere that is challenging to observe. It’s a complicated region where interactions between the sun, earth, our planet’s magnetic field, and other phenomena end up creating environmental conditions in which surface life can thrive, protected from the harsh space environment.

Intriguingly, Chu said, “There are metals in the atmospheres of other planetary bodies, such as Mars, and researchers look for Earth-like features on exoplanets as indicators for hospitable environments. Can these metal layers be one of these features?” 

Her team used a powerful atmospheric lidar to detect and measure very small quantities of particles in the high atmosphere. Lidar is similar to radar: a signal is sent out towards a target and the target returns part of that signal which is collected by a receiver. In radar, the signal is radio waves; in lidar, it is photons from a laser. The return signal can be analyzed to learn about the targets hit and the space that the beam traveled through. Chu’s group developed the highly sensitive instrument with funding from the National Science Foundation.

The National Science Foundation funded both the Boulder and McMurdo lidar projects, grants AGS-1452351, AGS-2029162, and OPP-1443726.

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ŷ���ڱ���Ƶ Boulder-led team is first to observe new equatorial wind patterns in Antarctica, revealing new connections in global circulation.

A CIRES-led team has uncovered a critical connection between winds at Earth’s equator and atmospheric waves 6,000 miles away at the South Pole. The team has found, for the first time, evidence of a Quasi-Biennial Oscillation (QBO)—an atmospheric circulation pattern that originates at the equator—at McMurdo, Antarctica.

The discovery highlights how winds in the deep tropics affect the remote South Pole, in particular the polar vortex, which can trigger outbreaks of cold weather patterns in mid latitudes. Scientists will be able to use this information to better understand the planet’s weather and climate patterns and fuel more accurate atmospheric models, the authors say.

“We have now seen how this atmospheric pattern propagates from the equator all the way to the high latitudes of Antarctica, showing how these far-away regions can be linked in ways we didn’t know about before,” said , a former CIRES research assistant who did this work at ŷ���ڱ���Ƶ Boulder, and lead author of the study out today in the .

“This can better our understanding of how large-scale atmospheric circulation works, and how patterns in one area of the world can ripple across the entire globe,” said Xinzhao Chu, CIRES Fellow, professor in the Ann & H.J. Smead Department of Aerospace Engineering Sciences at the University of ŷ���ڱ���Ƶ Boulder, and corresponding author on the new work.

Every two years or so, the QBO causes the stratospheric winds at Earth’s equator to switch direction, alternating between easterly and westerly. , a researcher at ŷ���ڱ���Ƶ’s Laboratory for Atmospheric and Space Physics (LASP) and a coauthor on the study, helped the team study the polar vortices, the massive swirls of cold air that spiral over each of Earth’s poles. The study reports that the Antarctic vortex expands during the QBO easterly phase and contracts during the westerly phase. The team suspects that when the QBO changes the polar vortex behavior, that, in turn, affects the behavior of atmospheric waves called gravity waves, which travel across different layers of the atmosphere. They identified specific kinds of changes in those gravity waves: The waves are stronger during the easterly period of the QBO and weaker when the QBO is westerly. 

For the last nine years, members of have spent long seasons at McMurdo Station, Antarctica, braving 24-hour darkness and frigid temperatures to operate custom lasers and measure patterns in Earth’s atmosphere. These long-term measurements, along with 21 years of NASA MERRA-2 atmospheric records, were critical to the new findings. Each QBO cycle takes years to complete, so long-term data streams are the only way to identify interannual connections and patterns.

“Atmospheric scientists can use this information to improve their models—before this nobody really knew how QBO impacts gravity waves in this polar region,” said , researcher at Clemson University and a coauthor on the study. “Researchers can use this information to better model and predict climate, including the variability of atmosphere and space and long-term change.”

“First Lidar Observations of Quasi-Biennial Oscillation-Induced Interannual Variations of Gravity Wave Potential Energy Density at McMurdo via a Modulation of the Antarctic Polar Vortex” published in Journal of Geophysical Research: Atmospheres on 26 July, 2020. Authors include: Zimu Li (CIRES), Xinzhao Chu (CIRES, ŷ���ڱ���Ƶ Boulder Ann & H.J. Smead Department of Aerospace Engineering Sciences), V. Lynn Harvey (ŷ���ڱ���Ƶ Laboratory for Atmospheric and Space Physics), Jackson Jandreau (CIRES, ŷ���ڱ���Ƶ Boulder Department of Aerospace Engineering Sciences, Smead Scholar), Xian Lu (Clemson University, Department of Physics and Astronomy), Zhibin Yu (CIRES, Harbin Institute of Technology), Jian Zhao (CIRES), Weichun Fong (CIRES).

We gratefully acknowledge the graduate students and research scientists who made contributions to the McMurdo lidar campaign, including many winter-over lidar scientists. We sincerely appreciate the staff of the United States Antarctic Program, McMurdo Station, Antarctica New Zealand and Scott Base for their superb support over the years.The lidars were housed in the Arrival Heights Observatory run by Antarctica New Zealand, and the lidar observations were enabled by a collaboration between the United States Antarctic Program and Antarctica New Zealand. This project was supported by the National Science Foundation grants OPP-0839091, OPP-1246405, and OPP-1443726.

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Headline Photo: (From left) Jackson Jandreau, Xinzhao Chu, Amanda Steckel; touchdown after a long and loud flight!
Above: Penguins really do just waddle around and slide on their bellies.

Greetings from Antarctica!

I can’t believe I am living and learning in one of the coolest (literally coldest) places on the planet. It is also one of the ugliest and simultaneously most beautiful. 50 acres of muddy ground and metal buildings, contrastingly surrounded by the breathtakingly beautiful frozen Ross Island.

I arrived here in December as a University of ŷ���ڱ���Ƶ Boulder aerospace PhD student and Smead Scholar working under professor Dr. Xinzhao Chu. She has been conducting research in Antarctica for years using two sophisticated lidar systems to do remote sensing of the upper atmosphere.

Making the Trip

Early explorers spent months of sea travel aboard steam vessels to do their science. In contrast, my colleague Amanda Steckel, Dr. Chu, and I flew here from Denver International in only about 24 hours. Our flights took us through Los Angeles, Auckland, and eventually to Christchurch, New Zealand, home of the US Antarctic Program (USAP) gateway to McMurdo Station.

At USAP we were issued our trademark red parkas, massively clunky “bunny boots”, and other extreme weather gear.

The next morning, we boarded a C130 aircraft headed straight to McMurdo on a very long, loud (and crowded) flight.

Life at the Bottom of the World

The living situation down here is pretty nice, considering you’re at the bottom of the world! Conditions have definitely improved a lot since the days when Robert Scott and Ernest Shackleton slept out in tents and sleeping bags.

All of us in the Lidar group are housed in the same dorm, a three-story building of suites with two per room.

The bed we saw inside Discovery Hut, built in 1902, vs. the accommodations we sleep in today.

If you aren’t bothered by the lack of fresh fruits, vegetables, and eggs, the meals provided by the galley staff are great.

It's cafeteria style, but there’s plenty of choices and they even make it possible to keep up most diets while you’re here (vegetarian, keto, gluten-free, etc). We look forward to mealtimes as a good opportunity to set work aside for a moment and enjoy a cup of coffee with coworkers and friends.

Frozen Holiday Season

The holiday season is a pretty big deal around McMurdo. From Christmas dinner, to holiday parties and art galleries, there are many activities centered around the season.

For celebrations, the galley breaks out special foods they’ve imported just for these events. They also had a Christmas party with a Santa sitting in the back of a Pisten Bully snowcat! All this was topped off with the annual Christmas Day baseball tournament held down by the sea ice.

  What a privilege it is to be among those able to follow in the footsteps of those early pioneers of science. 

A special treat was getting to step inside Scott’s 1902 Discovery Hut from one of his early voyages to Antarctica. Other than the weather, there isn’t much here to damage or break down the building over the years. We were excited to see that some of their original scientific experiments were still visible! What a privilege it is to be among those able to follow in the footsteps of those early pioneers of science.

Right next to the hut was a small group of Adélie Penguins out on the ice harassing the sunbathing seals.

Midnight Sun for New Years

The New Year celebration gets its own spotlight at McMurdo. The biggest celebration for this holiday is the annual Icestock, the “southernmost music festival in the world”, with bands made up of USAP staff and NSF grantees/employees performing until midnight.

Icestock was probably the longest I have spent outside in my whole time down here, and it was definitely not a warm day.

It was surreal counting down to 2020 with the sun still far above the horizon -- the next sunset in Antarctica won't be until March 3! New Year’s day itself saw a lot of hikers exploring the area around the base via the various hiking trails. I’m looking forward to venturing out for some hiking when the chance presents itself.

Lidar Systems

We are having a great time down here so far, enjoying the opportunity to learn about our own work, as well as the work our new friends are doing. Dr. Chu has run this campaign for almost 10 years now; it is a long campaign for many reasons, but one of the main goals is to identify how the behavior of the atmospheric layers relate to long-term solar and terrestrial events.

We’ve been learning about the lidar system all semester, and took a whole lidar class back in Boulder but are thrilled to finally get our hands on the actual system itself.

The lidar is being operated for the Antarctic winter by two of Dr. Chu's research assistants, Cissi Lin and Xianxin Li. Amanda and I are training so that in the coming years, we’ll be able to run the system over the winter. We’ve still got about six weeks left on this deployment, and there’s a lot of work to be done!

Good luck to our lidar team members over the long winter!
From left: Jandreau, Amanda Steckel, Cissi Lin, Xinzhao Chu, and Xianxin Li.

Hungry for more Antarctica? Check out Ian Geraghty's A Year on the Ice blog. Ian just wrapped up 13 months as a student researcher working in Antarctica, also under Xinzhao Chu.

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Ian Geraghty and Xinzhao Chu in Antarctica.

In the early 1900’s, Ross Island acted as a base for multiple Antarctic exploration expeditions led by the likes of Ernest Shackleton and Robert Falcon Scott. Remnants of the heroic age of Antarctic exploration can be found all over the island, along with the United States’ largest Antarctic research station, McMurdo Station, which is managed by the National Science Foundation.

Scenic is an understatement for the landscape around McMurdo. Across the McMurdo Sound, the Transantarctic mountains stretch out with glacial ice creeping slowly through the valleys enroute to the ocean. In the summer, pods of orcas can be spotted navigating the icy waters while seals and penguins lounge casually on ice floes. In the winter, the Milky Way can be seen with astounding clarity and auroras paint the sky vivid hues of green.

  The Milky Way can be seen with astounding clarity and auroras paint the sky vivid hues of green. 

Aside from the stunning surroundings, McMurdo is home to a unique community made up of some of the most interesting individuals I’ve ever met.

I arrived at McMurdo in October 2018 eager to experience as much as possible during my 13-month deployment as a research assistant. The group that I work with uses two sophisticated lidar systems to do remote sensing of the upper atmosphere.

Dr. Xinzhao Chu of the Cooperative Institute for Research in Environmental Sciences and the Smead Aerospace Engineering Sciences department at ŷ���ڱ���Ƶ Boulder designed these lidars and coordinates the project. Various members of the group have been at McMurdo continuously since 2010 operating the instruments with the ultimate goal of making observations over an entire solar cycle, which is approximately 11 years.

The lidar lab is located in Antarctica New Zealand’s building at Arrival Heights near McMurdo. The orange laser beam is the sodium lidar at a wavelength of 589 nm.

Using Lasers to Study the Atmosphere

The systems we use are called resonance fluorescence lidars. Basically, it’s a pulsed laser that we shoot into the sky. Meteors that enter the atmosphere burn up and deposit a whole layer of metal between ~80 – 115 km.

These two lidars are designed to observe specifically the iron and sodium in this layer. The lasers are tuned to wavelengths that excite these atoms and a telescope on the ground is used to count how much light is emitted as the atoms de-excite. With some special techniques, these photon counts can be processed into density, temperature, and even wind speed measurements. The data is used to study a variety of atmospheric properties at altitudes that are so high up that terrestrial weather and space weather processes influence each other.

A lot of work goes into a long-term observational campaign in Antarctica such as this. There are two of us at McMurdo working on the project this year. As lidar operators we need to be deeply familiar with all the hardware that makes up the lidar systems so that when equipment starts to fail we are prepared to fix it and get everything up and running again.

We work opposite 12-hour shifts so that we can have 24-hour coverage on any given day, but we don’t take data every day. Clouds scatter the laser too much so data collection is restricted to times when the sky is clear. Therefore, we are constantly monitoring the weather and prepared to drive to our lab which is located nearby McMurdo in an area called Arrival Heights.

Looking down on McMurdo Station

Life At McMurdo

Our group is just one of many doing science at McMurdo and the Albert P. Crary Science and Engineering Center (known locally just as “Crary”) is the hub of it all. In the summer, there is a nearly constant flow of researchers stopping through from New Zealand, the South Pole Station, and various field camps around Antarctica.

The research that takes place at McMurdo is very interdisciplinary and ŷ���ڱ���Ƶ Boulder has a huge presence here. Just this year I’ve had the pleasure of interacting with ŷ���ڱ���Ƶ graduate students and faculty that operate a meteor radar, collect biological samples in the McMurdo Dry Valleys, collect meteorites in the more remote parts of Antarctica, service automatic weather stations, and launch high-altitude balloons to study atmospheric aerosols. 

  The research that takes place at McMurdo is very interdisciplinary and ŷ���ڱ���Ƶ Boulder has a huge presence here.  

Most of the population at McMurdo, which can be greater than 1,000 people in the summer, aren’t scientists though. The majority of people are contractors like electricians, plumbers, cooks, and physicians, but at its core McMurdo is an entire community dedicated to performing and supporting world-class scientific research. The widespread mutual interest in the sciences and the comradery that comes with just making it to one of the more remote locations in the world makes for a friendly atmosphere on station.

After work hours people can relax at one of the bars, go hiking, or attend science lectures. On the weekends there are more community events like softball games, live music, and infamous holiday parties. Contrary to popular belief, there are plenty of opportunities to be social and stay busy down here.

24 Hours of Night

The summer at McMurdo is lively with 24 hours of daylight, mild temperatures, and hundreds of people, but the winter is a whole different story. The calm winter season is a nice respite from the hectic summer. For the most part, Crary is quiet except for the howling of fierce winds outside.

Taking in the last sunset before 4 months of darkness on April 22, 2019.

There’s less than a handful of scientists here and only 140 people in total on station. The Sun stays below the horizon between late April to August and as a result this is the time of year when we collect the best data. Since we are counting photons coming back from the upper atmosphere it’s best if we don’t have to compete with the light from the Sun. 

Antarctic winters are generally known for being cold and they live up to the hype. Once you get ambient temperatures around -40 ºF and wind speeds up to 50 mph the wind chill can hit – 70 ºF pretty easily. However, if you can avoid the gale force winds, the temperatures are pretty manageable with your issued extreme cold weather gear.

If you do take the time to layer up and go outside you’re rewarded with incredible views of the night sky. That being said, the first sunrise in August is going to be a welcome sight. I’m not even going to get into how stoked I am to eventually make it back to ŷ���ڱ���Ƶ.

These few paragraphs are a poor attempt to convey what it’s like to spend a year at McMurdo Station. It’s an esoteric place in the sense that only people who have been here really understand why it’s so special.

So, if the chance to come to “the ice” presents itself, get after it. If doing research in Antarctica is your goal, ŷ���ڱ���Ƶ Boulder is a great place to be. There are more opportunities than you’d expect. If you’re interested in travelling to Antarctica in a different capacity, a few of the companies that hire contractors are based out of Denver so there’s other opportunities nearby as well.

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Download the Lecture slides

Congratulations to professor Xinzhao Chu for being selected to give the 2019 CEDAR Prize Lecture. Chu received the honor for her scientific contributions to understanding coupling from the stratosphere to the mesosphere and lower thermosphere resulting from Lidar development and observations at McMurdo Station in Antarctica.

CEDAR, the Coupling, Energetics and Dynamics of Atmospheric Regions program, is a National Science Foundation initiative that provides funding to engineers and scientists investigating the make-up and behavior of the middle and upper atmosphere, which extends 6,000 miles above Earth’s surface.

This region where the tenuous atmosphere links to space is also home to orbiting military, communications and research satellites. Even the low concentrations of atmospheric gases can be significantly impacted by radiation and storms from the sun.

Previous CEDAR Prize Lecture honorees from Smead Aerospace Engineering Sciences include research professor Delores Knipp in 2017 and professor Jeff Forbes in 2014.

The 2019 CEDAR Summer Workshop is being held June 16-21 in Santa Fe, New Mexico.

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New research by Xinzhao Chu, a professor of Smead Aerospace and the Cooperative Institute for Research in Environmental Sciences, and her team shows gravity waves above Antarctica exhibit seasonal patterns that peak in winter, which could help researchers trace the source of the mysterious phenomenon.

Gravity waves are enormous vertical oscillations of air that propagate through the atmosphere like ripples in quiet water, and they are perpetually present in the Antarctic atmosphere.

Because these waves can create air turbulence and affect weather and climate by transporting energy and momentum between atmospheric layers, researchers have diligently searched for their sources.

Any gravity wave source must be constrained by wave properties observed in the atmospheric layers between 50 and 115 kilometers above Earth’s surface, where persistent gravity waves were first documented, and in the underlying stratosphere, where gravity waves have not yet been rigorously characterized.

To help fill this gap, Chu et al. report the results of a detailed statistical analysis of gravity wave characteristics in the stratosphere. Their data, which span from 2011 to 2015, are derived from the first multiyear, year-round measurements of temperature fluctuations made using an iron Boltzmann lidar system at the Arrival Heights observatory near Antarctica’s McMurdo Station.

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Ian Geraghty (AeroEngr’18) spent his first season in Antarctica in 2017. Now a research assistant at ŷ���ڱ���Ƶ, he’s part of an engineering team using laser equipment to study the mysteries of Earth’s atmosphere, including persistent gravity waves that could influence air circulation and weather patterns worldwide.

To obtain the most precise measurements, the delicate setup must be operated by hand around the clock, he said. This would be a true feat in Boulder, let alone at the ends of the earth. Geraghty and a colleague work in shifts, squeezing themselves into narrow alleys between banks of machinery filling an entire shack.

"It’s good to bring spare parts,” he said. “Because you can’t just go to the hardware store.”

Geraghty marvels over the many quirks of life at McMurdo. Hiking trails abound with curious penguins, and the night sky dazzles with aurora. Communication with the outside world is limited, and internet bandwidth is late ’90s-era slow. The accommodations are akin to army barracks or college dorms, with bunk beds and shared bathrooms down the hall

Researchers invariably lament the scarcity of fresh produce. When fruit and vegetables arrive by plane — infrequently, given weather patterns — it’s instantly the talk of camp.

But the rest of the menu is surprisingly good: Contractors in the restaurant-quality mess hall prepare impressive rotating fare such as Mongolian barbecue, Italian pasta and burgers. (The late celebrity chef Anthony Bourdain paid a visit in 2017.)

Much like summer camps elsewhere, there is a certain unshakable camaraderie among the 500 or so people who return to populate McMurdo every year.

“It’s funny because you’ll hear someone say they’re not coming back, and then you’ll see them next year, as usual,” says Xinzhao Chu, a professor and researcher at ŷ���ڱ���Ƶ’s Cooperative Institute for Research in Environmental Sciences (CIRES). She has led the atmospheric laser project since 2010 and has been traveling to Antarctica since 1999.

Chu marvels at her students’ willingness to travel so far and endure so much in the name of research that can only be accomplished in polar conditions.

“Everything that they are doing contributes to getting a bigger picture of the makings of the atmosphere,” she said.

Standing at the base of an Antarctic glacier in 2016, Pacifica Sommers watched the transport helicopter fly away, leaving her and a few fellow ŷ���ڱ���Ƶ biologists all alone in one of the coldest and most remote places on Earth.

“You do sort of realize at that point that a rescue wouldn’t be cheap or easy,” the postdoctoral researcher said.

It was quite a change of scenery for Sommers, who had completed her doctoral studies in the Arizona desert. She remembers standing sideways next to a Saguaro cactus to make use of its narrow band of shade in 100-plus-degree heat.

Now, she was strapping on crampons and setting up camp in the McMurdo Dry Valleys, the only area of Antarctica that isn’t permanently covered by snow. The dark, exposed soil on the hillsides resembles ŷ���ڱ���Ƶ’s alpine landscapes: beautiful, rugged, desolate.

But while the world’s coldest, windiest, driest continent may appear hostile to life, Sommers knows it’s quite the opposite. Small pockets in the surface known as cryoconite holes teem with microorganisms, all of which have adapted to survive an extreme environment. These naturally occurring test tubes could help scientists better understand evolutionary selection on Earth and even life on other planets.

“Ecosystems depend on historical contingency and randomness,” Sommers said. “We want to study how chance affects what biological communities look like and how they assemble.”

Antarctica’s 5.4 million square miles make for a pristine, if imposing, natural laboratory: All but 2 percent of the surface is covered in thick ice. The vast continent, nearly one and a half times the size of the contiguous U.S., has little in the way of commerce, government or human habitation. At the summer peak, in January, around 5,000 scientists and contractors occupy a handful of international stations near the coasts. In winter, when temperatures reach 50 degrees below zero, that population drops to roughly 1,000.

The thrill of scientific discovery in a place most people will never visit is matched by its challenges. The months-long work is grueling, the isolation is daunting and the days are long — literally, since the polar summer months bring near-constant sunshine. And yes, it’s pretty cold.

In Sommers’ first season on the ice, she wasn’t sure what to expect and admits she might have overpacked. By year two, she was a seasoned pro reveling in the occasionally balmy December weather.

“It can get up to 30 degrees or so,” she said. “We took our shoes off and played frisbee.”

ŷ���ڱ���Ƶ researchers usually begin arriving in November. Their first stop after a six-hour military aircraft flight from Christchurch, New Zealand, is McMurdo Station, the continent’s population hub, known colloquially as “town.” Year after year, this international outpost becomes a temporary home away from home.

Engineering professor Michael Gooseff (CivEng’98) is another Antarctic long-timer. He’s been making the trip annually for over two decades, first as a ŷ���ڱ���Ƶ graduate student, now as principal investigator of the National Science Foundation’s Long-Term Ecological Research (LTER) project, which studies the unique Dry Valleys ecosystem.

“Every time I go in the Valleys, it feels like a place where no one has been before,” Gooseff says. “There’s an obvious Martian analogue here. You fly over and see no sign of life, but on the ground and in the streams and lakes, you see beautiful microbial mats filled with color.”

Gooseff lauds ŷ���ڱ���Ƶ’s commitment to Antarctic studies and cites scientific operations on the continent broadly as a model of international collaboration. New Zealand, China, Italy and South Korea all have stations within an hour of McMurdo by helicopter, and it’s not uncommon for the scientists of several nations to help each other out — a kind of United Nations on ice.

“I think we all realize that it takes a lot of investment to work down here,” Gooseff said. “That raises the requirement on us to produce as much quality research as we can and get the results out there to the public in a relatable way.”

This year, Geraghty is headed back for another tour of duty. Except this time, when the last summer transport leaves in February, he won’t be on it. He and graduate student Zimu Li, will stay at McMurdo through October 2019 with a skeleton crew to manage the laser equipment in winter’s pervasive darkness.

“It’s a lot of responsibility,” he said. “But it feels good to work really hard and contribute to a big project with some of the most interesting people I’ve ever met.”

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ŷ���ڱ���Ƶ Boulder team led by Xinzhao Chu finds link between gravity waves in the upper and lower Antarctic atmosphere, helping create a clearer picture of global air circulation.

Two years after a CIRES and ŷ���ڱ���Ƶ Boulder team discovered a previously unknown class of waves rippling continuously through the upper Antarctic atmosphere, they’ve uncovered tantalizing clues to the waves’ origins. The interdisciplinary science team’s work to understand the formation of “persistent gravity waves” promises to help researchers better understand connections between the layers of Earth’s atmosphere—helping form a more complete understanding of air circulation around the world.

"A big picture of Antarctic gravity waves from the surface all the way to the thermosphere is emerging from the studies, which may help advance global atmospheric models,” said CIRES Fellow and ŷ���ڱ���Ƶ Boulder Professor of Aerospace Engineering Sciences Xinzhao Chu, lead author of the new study published in the Journal of Geophysical Research - Atmospheres. “The new understanding results from a series of journal publications, based on multiple years of lidar observations, many made by winter-over students, from Arrival Heights near McMurdo Station in Antarctica.”

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