clouds

Be There: The Kuo-Nan Liou Symposium

Highlighting Key Sessions at AMS 2024

The Kuo-Nan Liou Symposium at the 104th AMS Annual Meeting will celebrate Dr. Kuo-Nan Liou (1943-2021), a giant in the field of atmospheric physics who made crucial contributions in the areas of atmospheric radiation, remote sensing, and the greenhouse impacts of clouds and aerosols. Liou (pictured at right, image courtesy of Penny Jennings), received numerous accolades during his career, including the AMS’s Carl-Gustaf Rossby Research Medal and Charney Award, and he was part of the Intergovernmental Panel on Climate Change team who received the Nobel Peace Price in 2007.

We asked Symposium Co-Chair Ping Yang, University Distinguished Professor and David Bullock Harris Chair in Geosciences at Texas A&M University, about the Symposium and Dr. Liou’s impact. Here are some of his answers:

Dr. Kuo-Nan Liou (image credit: Penny Jennings)

Why are the areas of Dr. Liou’s research so important to understand right now?

As one of the most accomplished atmospheric scientists in the world, Dr. Liou made seminal contributions to atmospheric and climate sciences in many areas, particularly in atmospheric radiation. His radiative transfer model has been widely used in weather and climate models and satellite remote sensing implementations, and thus plays a central role in determining the radiation budget of the earth-atmosphere system and cloud-aerosol-radiation interactions and feedback in a changing world.

Radiative transfer is important because almost all the energy that drives the Earth’s atmosphere and ocean currents originates from the sun. Therefore, the climate of the Earth-atmosphere system is mainly determined by the radiation balance at the top of the atmosphere and the surface since radiation is the only mechanism by which the Earth-atmosphere system gains or loses energy.

What can attendees expect from the Symposium?

This symposium honors the legacy of Dr. Kuo-Nan Liou by bringing together researchers to share knowledge, foster collaborations and address current challenges in the fields where Dr. Kuo-Nan Liou left a lasting impact. Attendees, both in-person and virtual, can benefit from gaining insights into the latest research and advancements in these areas. Session topics include “Interactions Among Climate, Radiation, Clouds, Aerosols, and Surface”, “Radiative Transfer Theory & Spectroscopy,” “Remote Sensing of Clouds, Aerosols, and Surface Properties,” and “Light Scattering and Applications.” The Symposium will provide a platform for networking and engaging with experts and a forum for disseminating cutting-edge research findings.

The Symposium will delve into the forefront issues within these research areas. Noteworthy presentation topics include the lidar remote sensing of snow depth and density, sub-millimeter-wave remote sensing of ice clouds, Tibetan Plateau snowpack loss and its connection to extreme events, and more.

The first session aligns with the central focus of the 2024 AMS Annual Meeting, “Living in a Changing Environment.” It features invited speakers Drs. Ruby Leung, Dennis Hartmann, V. Ramaswamy, Zhanqing Li, Jonathan Jiang, and Yongkang Xue. 

How did Dr. Liou influence the fields of atmospheric and climate science?

Dr. Liou’s work left a profound mark on the atmospheric and climate sciences due to his seminal contributions to radiative transfer, atmospheric optics, cloud-aerosol-radiation-climate interactions, and remote sensing. He was a pioneering researcher who demonstrated that atmospheric radiation should no longer be consigned to the fringes of meteorology, but instead should take a central place in the new world of climate science.

His book, “An Introduction to Atmospheric Radiation,” now in its second edition (with the first edition published in 1980), has been an invaluable resource for students and researchers around the world studying atmospheric radiation and its applications in climate science and remote sensing. Accepting the Rossby Medal in 2018, Prof. Liou talked about how his own early-career exposure to books like Chandrasekhar’s “Radiative Transfer” and Born & Wolf’s “Principles of Optics” spurred his innovations. For example, his simplified solutions for understanding solar and heat energy transfer problems, and his application of geometric optics to understand the scattering, absorption, and polarization properties of soot aerosols and irregular ice crystals.

He also humbly thanked his graduate students at the University of Utah and UCLA, saying, “They deserve to share, in equal measure, any recognition I have received, including this great honor from AMS.” We, the organizers of the Symposium, in turn are grateful to Dr. Liou. Along with his exceptional impact on the atmospheric sciences, he was a true role model as a leader and educator.

Kuo-Nan Liou receiving the Carl-Gustaf Rossby Research Medal at the 2018 AMS Annual Meeting and celebrating with his family, students, and colleagues. Photos provided by Liou Symposium co-chairs.

The Kuo-Nan Liou Symposium will be held Tuesday, 30 January, 2024 at the AMS 104th Annual Meeting, in Baltimore and online; it will feature invited presentations and a poster session, along with a special luncheon. Learn more about the Symposium and view the program.

When Art Is a Matter of (Scientific) Interpretation

We’ve seen plenty of examples of scientists inspiring art at AMS conferences. It is also true that art can inspire scientists, as in the kick-off press conference at this week’s European Geophysical Union General Assembly in Vienna, Austria.
The_ScreamA team of scientists came forward with a new hypothesis about the origins of one of the icons of Western art–Edvard Munch’s The Scream. Since 1892, the man melting down on a bridge under a wavy, blood-red Oslo sunset has been a pillar of the modern age precisely because it expresses interior mentality more than objective observation. Or so art history tells us.
To be fair, some art historians also have made clear that there are honest clouds in Munch’s painting. In a 1973 monograph, the University of Chicago’s Reinhold Heller acknowledged Munch’s “faithfulness to meteorological and topographical phenomena” in a precursor canvas, called Despair. Even so, Heller went on to say that Munch’s vision conveyed “truthfulness solely in its reflection of the man’s mood.”
Take a Khan Academy course on the history of art and you’ll learn that Munch was experiencing synesthesia—“a visual depiction of sound and emotion….The Scream is a work of remembered sensation rather than perceived reality.”
Leave it to physical scientists, then, to remind us that nature, as an inspiration for artists, is far stranger than art historians imagine. Indeed, faced with The Scream, scientists have been acting just like scientists: iterating through hypotheses about what the painting really shows.
In a 2004 article in Sky and Telescope magazine, Russell Doescher, Donald Olson, and Marilynn Olson argued that Munch’s vision was inspired by sunsets inked red after the eruption of Krakatau in 1882.
More recently, atmospheric scientists have debunked the volcanic hypothesis and posited alternatives centered on specific clouds. In his 2014 book on the meteorological history of art, The Soul of All Scenery, Stanley David Gedzelman points out that the mountains around Oslo could induce sinuous, icy wave clouds with lingering tint after sunset. The result would be brilliant undulations very much like those in the painting.
At EGU this week, Svein Fikke, Jón Egill Kristjánsson, and Øyvind Nordli contend that Munch was depicting much rarer phenomenon: nacreous, or “mother of pearl,” clouds in the lower stratosphere. They make their case not only at the conference this week, but also in an article just published in the U.K. Royal Meteorological Society’s magazine, Weather.
Munch never revealed exactly when he saw the sunset that startled him. As a result, neither cloud hypothesis is going to be confirmed definitively.
Indeed, to a certain extent, both cloud hypotheses rest instead on a matter of interpretation about the timing of the painting amongst Munch’s works, about his diary, and other eyewitness accounts.
The meteorology, in turn, is pretty clear: The Scream can no longer be seen as solely a matter of artistic interpretation.
 

A Good Climate for Looking at Clouds

How much do we know about clouds and the effects they have on climate change? It’s a lingering source of uncertainty, with as many questions as answers. No wonder the National Science Foundation calls them “The Wild Card of Climate Change” on its new website about the effect of clouds in climate.
The site is good place to start thinking about this complicated issue. The NSF page features videos of cloud experts like David Randall of Colorado State University and AMS President Peggy LeMone of NCAR, as well as a slide show, animations, articles, and other educational material that address some of most salient cloud/climate questions, such as: Will clouds help speed or slow climate change? Why is cloud behavior so difficult to predict? And how are scientists learning to project the behavior of clouds?
The impression one gets from the website about the progress of the science in this area may vary depending on your point of view, but Randall, for one, sounds about as optimistic as you can get. In his video, he admits that optimism is a job requirement for climate modelers, but in his assessment, “We’re not in the infant stages of understanding [clouds] any more; we’re in first or second grade, and on the way to adolescence.” His hope for solving their role in climate and representing cloud effects in climate modeling rests in part on better computers and in part on the numerous bright people entering the field now, ready to overshadow the work of their mentors.
The AMS Annual Meeting in Seattle will be a good occasion to dig deeper at the roots of Randall’s optimism and sample some of the emerging solutions to the cloud/climate relationship. For example, Andrei Sokolov and Erwan Monier of MIT will discuss the influence that adjusting cloud feedback has on climate sensitivity  (Wednesday, 26 January, 11:30 a.m. in Climate Variability and Change). Basically, they’re using small adjustments to the cloud cover used to calculate surface radiation in a model to create a suite of results–an ensemble. The range of results better reflects the sensitivity of climate observed in the 20th century better than some other methods of creating ensembles, such as adjusting the model physics.
Randall says in his video that early predictions about climate change are already coming to pass and this leads to optimism that more predictions will verify well in the coming years as we scrutinize climate more and more closely. This of course presupposes sustained efforts to observe and verify. Laying the groundwork for this task–and for thus better climate models–are Stuart Evans (University of Washington) and colleagues in a study they are presenting in Seattle. According to their abstract, “Improving cloud parameterizations in large scale models hinges on understanding the statistical connection between large scale dynamics and the cloud fields they produce.” Their study focuses on the relationship between synoptic-scale dynamic patterns and cloud properties (Monday, 24 January, 11 a.m. in Climate Variability and Change). Evans et al. dig through 13 years of cloud vertical radar profiles from the US Southern Plains site of the DOE ARM program and relate it to atmospheric “states”, thus providing a metric for evaluating how well climate models relate cloudiness to radiation and other surface properties.
While Evans and colleagues use upward looking remote sensing, Joao Teixeira (JPL/Cal Tech) and coauthors look down at boundary layer cloudiness from above–using satellites. They expect to show how new methodologies with satellite data can improve the way low level clouds are parameterized in climate models (Thursday, 27 January, 9:30 a.m., in Climate Variability and Change). A recent workshop at Cal Tech on space-based studies of this problem stated:

Clouds in the boundary layer, the lowermost region of the atmosphere adjacent to the Earth’s surface, are known to play the key role in climate feedbacks that lead to these large uncertainties. Yet current climate models remain far from realistically representing the cloudy boundary layer, as they are limited by the inability to adequately represent the small-scale physical processes associated with turbulence, convection and clouds.

The lack of realism of the models at this low level is compounded by the lack of global observing of what goes on underneath the critical low-level cloud cover–hence the effort of Teixeira et al. (and others) to “leverage” satellite observing, with its global reach, to improve understanding of low level thermodynamics in the name of improving climate simulations.

From the new NSF web page on clouds and climate, this picture shows a series of mature thunderstorms in southern Brazil. Photo credit: Image Science & Analysis Laboratory, NASA Johnson Space Center

How to Spot a Cloud Enthusiast

Sunday night is movie night at this year’s Atlanta meeting. While weather-related flicks will be playing near continuously at the DVD theater this week, the 7 p.m. showing Sunday is U.S. premiere of the BBC4 program, “Cloudspotting,” a paean to the beauties, mysteries, and wonders of the sky. Narrator Gavin Pretor-Pinney, founder of the Cloud Appreciation Society, draws on art, science, mythology, and a deep love of the sky that will undoubtedly resonate with AMS attendees and their families. We suspect there will be plenty of true cloudspotters in the audience.
For a brief sample of the profound identification with the skies that Pretor-Pinney brings to this visually stunning 90-minute show, check out this little audio clip of him speaking at a recent author’s talk at Google, promoting his book, The Cloudspotter’s Guide.
Or follow up after the movie, when you have time, for the whole lecture:

Shedding New Light on Night-Shining Clouds

Photo credit: Pekka Parviainen

Scientists have been making new progress in solving the mysteries of noctilucent clouds [also known as Polar Mesospheric Clouds (PMCs)], thanks to NASA’s Aeronomy of Ice in the Mesosphere (AIM) satellite. AIM recently recorded a series of complete polar seasons of these clouds, which form in the mesosphere and are only visible on Earth when illuminated by sunlight from below the horizon. The satellite’s findings “have altered our previous understanding of why PMCs form and vary,” according AIM principal investigator James Russell III of Hampton University in Virginia.

AIM observed the PMCs in each hemisphere’s summer season at all longitudes and over a latitude range of 60°–85°; this video shows the clouds in the northern skies from late May to mid-August of 2009.

AIM’s data revealed that the clouds form and dissipate at very high speeds and may be affected by high-altitude weather systems.
“The cloud season abruptly turns on and off going from no clouds to near complete coverage in a matter of days, with the reverse pattern occurring at the season end,” Russell said.  Russell likens this seasonal on-off switch to a  “geophysical light bulb” in the presentation he will make about the new findings at the Space Weather Symposium during the AMS Annual Meeting in Atlanta (Tuesday, 8:30 AM, B303).
Noctilucent clouds are made of ice crystals that form when water vapor condenses onto dust particles at extremely cold temperatures (around -210° to -235°F). Scientists are using the new imagery as well as computer models to figure out more about what conditions trigger the clouds. So far, the new data indicate that high altitude temperature determines the onset, variability, and end of the cloud season. Satellite imagery also seems to show relationships to planetary waves as well as smaller scale gravity waves in the atmosphere.