RAL

High-resolution regional modeling (no supercomputer needed)

Annual precipitation over Colorado as modeled by the low-resolution, global Community Earth System Model (top) compared to the high-resolution, regional Weather Research and Forecasting model (below). (Images courtesy Ethan Gutmann, NCAR.) February 13, 2017 | In global climate models, the hulking, jagged Rocky Mountains are often reduced to smooth, blurry bumps. It's a practical reality that these models, which depict the entire planet, typically need to be run at a relatively low resolution due to constraints on supercomputing resources. But the result, a virtual morphing of peaks into hills, affects the ability of climate models to accurately project how precipitation in mountainous regions may change in the future — information that is critically important to water managers.To address the problem, hydrologists have typically relied on two methods to "downscale" climate model data to make them more useful. The first, which uses statistical techniques, is fast and doesn't require a supercomputer, but it makes many unrealistic assumptions. The second, which uses a high-resolution weather model like the Weather Research and Forecasting model (WRF), is much more realistic but requires vast amounts of computing resources.Now hydrologists at the National Center for Atmospheric Research (NCAR) are developing an in-between option: The Intermediate Complexity Atmospheric Research Model (ICAR) gives researchers increased accuracy using only a tiny fraction of the computing resources."ICAR is about 80 percent as accurate as WRF in the mountainous areas we studied," said NCAR scientist Ethan Gutmann, who is leading the development of ICAR. "But it only uses 1 percent of the computing resources. I can run it on my laptop."Drier mountains, wetter plainsHow much precipitation falls in the mountains — and when — is vitally important for communities in the American West and elsewhere that rely on snowpack to act as a frozen reservoir of sorts. Water managers in these areas are extremely interested in how a changing climate might affect snowfall and temperature, and therefore snowpack, in these regions.But since global climate models with low resolution are not able to accurately represent the complex topography of mountain ranges, they are unsuited for answering these questions.For example, as air flows into Colorado from the west, the Rocky Mountains force that air to rise, cooling it and causing moisture to condense and fall to the ground as snow or rain. Once these air masses clear the mountains, they are drier than they otherwise would have been, so there is less moisture available to fall across Colorado's eastern plains.Low-resolution climate models are not able to capture this mechanism — the lifting of air over the mountains — and so in Colorado, for example, they often simulate mountains that are drier than they should be and plains that are wetter. For a regional water manger, these small shifts could mean the difference between full reservoirs and water shortages."Climate models are useful for predicting large-scale circulation patterns around the whole globe, not for predicting precipitation in the mountains or in your backyard," Gutmann said.Precipitation in millimeters over Colorado between Oct. 1 and May 1 as simulated by the Weather Research and Forecasting model (WRF), the Intermediate Complexity Atmospheric Research model (ICAR), and the observation-based Parameter-Elevation Regressions on Independent Slopes Model. (Images courtesy Ethan Gutmann.)A modeling middle groundA simple statistical fix for these known problems may include adjusting precipitation data to dry out areas known to be too wet and moisten areas known to be too dry. The problem is that these statistical downscaling adjustments don't capture the physical mechanisms responsible for the errors. This means that any impact of a warming climate on the mechanisms themselves would not be accurately portrayed using a statistical technique.That's why using a model like WRF to dynamically downscale the climate data produces more reliable results — the model is actually solving the complex mathematical equations that describe the dynamics of the atmosphere. But all those incredibly detailed calculations also take an incredible amount of computing.A few years ago, Gutmann began to wonder if there was a middle ground. Could he make a model that would solve the equations for just a small portion of the atmospheric dynamics that are important to hydrologists — in this case, the lifting of air masses over the mountains — but not others that are less relevant?"I was studying statistical downscaling techniques, which are widely used in hydrology, and I thought, 'We should be able to do better than this,'" he said. "'We know what happens when you lift air up over a mountain range, so why don’t we just do that?'"Gutmann wrote the original code for the model that would become ICAR in just a few months, but he spent the next four years refining it, a process that's still ongoing.100 times as fastLast year, Gutmann and his colleagues — Martyn Clark and Roy Rasmussen, also of NCAR; Idar Barstad, of Uni Research Computing in Bergen, Norway; and Jeffrey Arnold, of the U.S. Army Corps of Engineers — published a study comparing simulations of Colorado created by ICAR and WRF against observations.The authors found that ICAR and WRF results were generally in good agreement with the observations, especially in the mountains and during the winter. One of ICAR's weaknesses, however, is in simulating storms that build over the plains in the summertime. Unlike WRF, which actually allows storms to form and build in the model, ICAR estimates the number of storms likely to form, given the atmospheric conditions, a method called parameterization.Even so, ICAR, which is freely available to anyone who wants to use it, is already being run by teams in Norway, Austria, France, Chile, and New Zealand."ICAR is not perfect; it's a simple model," Gutmann said. "But in the mountains, ICAR can get you 80 to 90 percent of the way there at 100 times the speed of WRF. And if you choose to simplify some of the physics in ICAR, you can get it close to 1,000 times faster."About the articleTitle: The Intermediate Complexity Atmospheric Research Model (ICAR)Authors: Ethan Gutmann, Idar Barstad, Martyn Clark, Jeffrey Arnold, and Roy RasmussenJournal: Journal of Hydrometeorology, DOI: 10.1175/JHM-D-15-0155.1Funders:U.S. Army Corps of EngineersU.S. Bureau of ReclamationCollaborators:Uni Research Computing in NorwayU.S. Army Corps of EngineersWriter/contact: Laura Snider, Senior Science Writer

Scientists take to the skies to test cloud seeding

February 7, 2017 | Does cloud seeding successfully increase snowfall? This winter, scientists with the National Center for Atmospheric Research (NCAR) are taking part in a field project in Idaho that will help answer the question.The project, called SNOWIE (Seeded and Natural Orographic Wintertime Clouds — the Idaho Experiment), is taking place from Jan. 7 to March 17 in the Payette Basin region north of Boise. A public-private partnership, SNOWIE is led by scientists at the University of Wyoming and other universities in collaboration with NCAR, with funding from the National Science Foundation (which is NCAR's sponsor) and the Idaho Power Company.The research team is using airborne and ground-based radars, high-resolution snow gauges, and computer modeling to gain insights into what happens after clouds are seeded with silver iodide. Snow from winter storms develops when ice crystals form on dust and other particles known as "ice nuclei." In cloud seeding, silver iodide is used to make artificial nuclei to encourage snowflakes to form.Silver iodide is released during the SNOWIE field project in such a way that it disperses downwind to the east, with its highest concentrations forming a zigzag pattern (shown in red). This allows scientists to fly a research aircraft from west to east through both seeded and unseeded regions and compare differences in ice crystal formation. (Image by Lulin Xue, ©UCAR. This image is freely available for media & nonprofit use.)NCAR scientists are focusing much of their work on observations taken by a University of Wyoming King Air plane that is flying though plumes of silver iodide released by a seeding aircraft. The silver iodide disperses downwind in a zigzag pattern, enabling the King Air to intercept it multiple times. The scientists will compare the formation of ice crystals in regions of clouds that are seeded with those that are not.The results can also be used to improve the NCAR-based Weather Research and Forecasting model (WRF), especially its simulation of cloud microphysics related to cloud seeding.Although scientists think that cloud seeding and other types of weather modification can increase precipitation in certain circumstances, the effects are difficult to quantify."NCAR's role in these weather modification experiments is to provide an unbiased viewpoint," said NCAR scientist Sarah Tessendorf, a principal investigator on SNOWIE. "The project uses observations and computer models to determine what is happening during a cloud seeding program and whether it is effective as a water augmentation tool."For more about the project, see the NSF news release.Writer/contactDavid Hosansky, Manager of Media RelationsFundersNational Science FoundationIdaho Power CompanyPartnersUniversity of WyomingIdaho Power CompanyUniversity of Colorado BoulderUniversity of Illinois at Urbana-ChampaignBoise State UniversityCenter for Severe Weather ResearchWeather Modification, Inc.

RAL Seminar: Lightning Safety Impacts on Airline and Airport Operations, Dr. Matthias Steiner

Thunderstorms and lightning pose a safety risk to personnel working outdoors. Airport and airline operators, therefore, employ safety procedures that include observations and warnings of the onset and duration of lightning hazards. Ramp closures (i.e., bringing people inside) are needed to ensure the safety of outdoor personnel servicing gate-side aircraft. Yet halting outdoor work delays air traffic and can cause ripple effects beyond the impacted airport.

RAL Seminar: Coupling the Physical and Social Sciences Toward Understanding the Transmission Dynamics of Aedes-Borne Viruses

Aedes aegypti mosquitoes are the primary vectors for dengue, yellow fever, chikungunya and Zika viruses. In recent decades, this mosquito and a closely related vector, Aedes albopictus, have expanded rapidly in the Americas, including the United States due to changing environmental and human conditions. Viruses transmitted by Aedes mosquitoes are a growing threat in the United States as evidenced by the proliferation of dengue viruses and the recent introductions of Zika and chikungunya viruses.

Two NCAR scientists honored by American Geophysical Union

BOULDER, Colo. — Martyn Clark, senior scientist at the National Center for Atmospheric Research (NCAR), will be honored next week as a Fellow of the American Geophysical Union (AGU) for his exceptional contribution to Earth science.Clark is an expert in the numerical modeling and prediction of hydrologic processes. His current research includes developing new modeling methods to improve streamflow forecasts and better understand climate change impacts on regional water resources. Clark, who grew up in Christchurch, New Zealand, has authored or co-authored 135 journal articles since receiving his Ph.D. from the University of Colorado in 1998.NCAR Senior Scientist Martyn Clark (©UCAR. Photo by Carlye Calvin. This image is freely available for media & nonprofit use.)"This well-deserved honor reflects Martyn's eminent work in the increasingly critical area of water-resource prediction and management," said NCAR Director James W. Hurrell.Clark said he was delighted to see NCAR's hydrologic modeling recognized. "Hydrology is beginning to play a much stronger role in addressing important interdisciplinary science questions about Earth System change, such as how changes in the terrestrial water cycle affect biological productivity and how groundwater can buffer water stress in ecosystems and human societies. It's exciting to advance modeling capabilities in these areas."NCAR Senior Scientist Bette Otto-Bliesner. (©UCAR. Photo by Carlye Calvin. This image is freely available for media & nonprofit use.)Clark is among 60 individuals from eight countries recognized as Fellows this year; only one in one thousand AGU members receive this recognition in any given year. Nearly 40 percent of this year's fellows are from the 110 member colleges and universities of the University Corporation for Atmospheric Research (UCAR), which manages NCAR. This year's class will be honored next Wednesday at the 2016 AGU Fall Meeting in San Francisco.NCAR Senior Scientist Bette Otto-Bliesner, who was named an AGU Fellow last year, is being honored by her peers in the Paleoceanography and Paleoclimatology Focus Group and Ocean Sciences Section by being asked to give the 2016 Emiliani Lecture. She will give the lecture next Wednesday at the AGU Fall Meeting on the topic of "Resolving Some Puzzles of Climate Evolution Since the Last Glacial Maximum: A Melding of Paleoclimate Modeling and Data."The AGU, dedicated to advancing Earth and space sciences for the benefit of society, is a not-for-profit, professional organization representing 60,000 members in more than 140 countries. 

Extreme downpours could increase fivefold across parts of the U.S.

BOULDER, Colo. — At century's end, the number of summertime storms that produce extreme downpours could increase by more than 400 percent across parts of the United States — including sections of the Gulf Coast, Atlantic Coast, and the Southwest — according to a new study by scientists at the National Center for Atmospheric Research (NCAR).The study, published today in the journal Nature Climate Change, also finds that the intensity of individual extreme rainfall events could increase by as much as 70 percent in some areas. That would mean that a storm that drops about 2 inches of rainfall today would be likely to drop nearly 3.5 inches in the future."These are huge increases," said NCAR scientist Andreas Prein, lead author of the study. "Imagine the most intense thunderstorm you typically experience in a single season. Our study finds that, in the future, parts of the U.S. could expect to experience five of those storms in a season, each with an intensity as strong or stronger than current storms."The study was funded by the National Science Foundation (NSF), NCAR's sponsor, and the Research Partnership to Secure Energy for America.“Extreme precipitation events affect our infrastructure through flooding, landslides and debris flows,” said Anjuli Bamzai, program director in NSF’s Directorate for Geosciences, which funded the research.  “We need to better understand how these extreme events are changing. By supporting this research, NSF is working to foster a safer environment for all of us.”The figure shows the expected increase in the number of summertime storms that produce extreme precipitation at century's end compared to the period 2000 - 2013. (©UCAR. Courtesy Andreas Prein, NCAR. This image is freely available for media & nonprofit use.)A year of supercomputing timeAn increase in extreme precipitation is one of the expected impacts of climate change because scientists know that as the atmosphere warms, it can hold more water, and a wetter atmosphere can produce heavier rain. In fact, an increase in precipitation intensity has already been measured across all regions of the U.S. However, climate models are generally not able to simulate these downpours because of their coarse resolution, which has made it difficult for researchers to assess future changes in storm frequency and intensity.For the new study, the research team used a new dataset that was created when NCAR scientists and study co-authors Roy Rasmussen, Changhai Liu, and Kyoko Ikeda ran the NCAR-based Weather Research and Forecasting (WRF) model at a resolution of 4 kilometers, fine enough to simulate individual storms. The simulations, which required a year to run, were performed on the Yellowstone system at the NCAR-Wyoming Supercomputing Center.Prein and his co-authors used the new dataset to investigate changes in downpours over North America in detail. The researchers looked at how storms that occurred between 2000 and 2013 might change if they occurred instead in a climate that was 5 degrees Celsius (9 degrees Fahrenheit) warmer — the temperature increase expected by the end of the century if greenhouse gas emissions continue unabated.Prein cautioned that this approach is a simplified way of comparing present and future climate. It doesn't reflect possible changes to storm tracks or weather systems associated with climate change. The advantage, however, is that scientists can more easily isolate the impact of additional heat and associated moisture on future storm formation."The ability to simulate realistic downpours is a quantum leap in climate modeling. This enables us to investigate changes in hourly rainfall extremes that are related to flash flooding for the very first time," Prein said. "To do this took a tremendous amount of computational resources."Impacts vary across the U.S.The study found that the number of summertime storms producing extreme precipitation is expected to increase across the entire country, though the amount varies by region. The Midwest, for example, sees an increase of zero to about 100 percent across swaths of Nebraska, the Dakotas, Minnesota, and Iowa. But the Gulf Coast, Alabama, Louisiana, Texas, New Mexico, Arizona, and Mexico all see increases ranging from 200 percent to more than 400 percent.The study also found that the intensity of extreme rainfall events in the summer could increase across nearly the entire country, with some regions, including the Northeast and parts of the Southwest, seeing particularly large increases, in some cases of more than 70 percent.A surprising result of the study is that extreme downpours will also increase in areas that are getting drier on average, especially in the Midwest. This is because moderate rainfall events that are the major source of moisture in this region during the summertime are expected to decrease significantly while extreme events increase in frequency and intensity. This shift from moderate to intense rainfall increases the potential for flash floods and mudslides, and can have negative impacts on agriculture.The study also investigated how the environmental conditions that produce the most severe downpours might change in the future. In today's climate, the storms with the highest hourly rainfall intensities form when the daily average temperature is somewhere between 20 and 25 degrees C (68 to 77 degrees F) and with high atmospheric moisture. When the temperature gets too hot, rainstorms become weaker or don't occur at all because the increase in atmospheric moisture cannot keep pace with the increase in temperature. This relative drying of the air robs the atmosphere of one of the essential ingredients needed to form a storm.In the new study, the NCAR scientists found that storms may continue to intensify up to temperatures of 30 degrees C because of a more humid atmosphere. The result would be much more intense storms."Understanding how climate change may affect the environments that produce the most intense storms is essential because of the significant impacts that these kinds of storms have on society," Prein said.About the articleTitle: The future intensification of hourly precipitation extremesAuthors: Andreas F. Prein, Roy M. Rasmussen, Kyoko Ikeda, Changhai Liu, Martyn P. Clark, and Greg J. HollandJournal: Nature Climate Change, DOI: 10.1038/NCLIMATE3168Writer:Laura Snider, Senior Science Writer and Public Information Officer

A favorable forecast for Kenyan students

November 30, 2016 | As scientists expand a program to provide critically needed weather observations in developing countries, they are forging a partnership with local schoolchildren and their teachers.The students and teachers are helping to oversee and maintain innovative weather stations, built largely with 3D-printed parts, at four schools in Kenya. By transmitting information about temperature, rainfall, and other weather parameters, the stations can help alert communities to floods and other potential disasters, as well as provide improved weather forecasts to local farmers, who are deciding when to plant and fertilize crops.NCAR scientist Paul Kucera describes the various components of the 3D-PAWS at the Sirua Aulo Maasai High School. (©UCAR. Photo by Kristin Wegner. This image is freely available for media & nonprofit use.) The weather stations, known as 3D-PAWS (for 3D-Printed Automated Weather Stations), are built with components that can be easily replaced if they wear out in the field. They were designed by weather experts at the National Center for Atmospheric Research (NCAR) and its managing entity, the University Corporation for Atmospheric Research (UCAR)."In my 30 years of doing fieldwork, this is one of the best deployments I've ever had," said NCAR scientist Paul Kucera. "At every school, we were joined by hundreds of students and dozens of teachers who wanted to learn more about the weather stations and the value of these forecasts."The weather stations were installed as a partnership with the Global Learning and Observations to Benefit the Environment (GLOBE) program, an international science and education initiative that encompasses tens of thousands of schools. This approach means that 3D-PAWS serves the dual purpose of educating students and improving forecasts."This is a great partnership to now extend our weather stations to schools," said Kristin Wegner, a project manager with the GLOBE Implementation Office, based at UCAR. "There is so much enthusiasm among the teachers and students because it's such a great learning tool as well as helping their communities."Students will learn about local weather and climate by comparing their weather observations to those taken at other schools using science protocols established by GLOBE. They can also assess the impacts of climate change on society and the environment, as well as see how the observations help with farming, flood prediction, and other applications.The installments took place during GLOBE's biannual Lake Victoria Learning Expedition, in which students and scientists from around the world explore the environment around the lake and discuss potential research collaborations. The expedition was coordinated by GLOBE Africa Regional Coordinator Mark Brettenny and  GLOBE Kenya Assistant Country Coordinator Charles Mwangi. Schools also received equipment donated from Youth Learning as Citizen Environmental Scientists.Needed: more stationsLike many developing countries, Kenya does not have detailed forecasts, partly because weather stations are scarce. The density of stations in Africa is eight times lower than recommended by the World Meteorological Organization. Building out a network can be prohibitively expensive, with a single commercial weather station often costing $10,000 to $20,000, plus ongoing funding for maintenance and replacing worn-out parts.To fill this need, UCAR and NCAR scientists have worked for years to come up with a weather station that is inexpensive and easy to fix and can be adapted to the needs of the host country. The resulting 3D-PAWS are constructed out of plastic parts that are custom designed and can be run off a 3D printer, along with off-the-shelf sensors and a basic, credit card-sized computer developed for schoolchildren.The total cost is about $300 per station. As the stations age, the host country can easily have replacement parts printed.Funding for the project comes from the U.S. Agency for International Development's Office of Foreign Disaster Assistance and the U.S. National Weather Service.Scientists installed the 3D-PAWS in Zambia earlier this year. Kenya is the second country to receive them."We're looking forward to installing more stations," Wegner said. "Additional schools are already asking about them."FundersU.S. Agency for International Development's Office of Foreign Disaster Assistance U.S. National Weather Service.PartnerGlobal Learning and Observations to Benefit the Environment (GLOBE)Writer/contact:David Hosansky, Manager of Media Relations

MMM/RAL Seminar: Stochastic Ice Nucleation and its Effect on the Microphysical Properties of Mixed-Phase Stratiform Cloud

Stochastic ice nucleation and its effect on the microphysical properties of mixed-phase stratiform cloud

 Fan Yang
Atmospheric Sciences Program, Michigan Technological University

RAL Seminar An Overview of Air Force Weather Cloud Analysis and Forecast System and Plans for the Future

Title: An Overview of Air Force Weather Cloud Analysis and Forecast System and Plans for the Future
Presenter: Dr. Timothy Nobis, Chief Scientist SEMS III – Northrop Grumman

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