An article by Atmospheric Technologies Group (ATG) scientists Dr. Stephen Noble, Dr. Brian Viner, Dr. Robert Buckley, and Dr. Steven Chiswell has been published in Atmosphere - an international, peer-reviewed scientific journal. The article titled ‘Skill of Mesoscale Models in Forecasting Springtime Macrophysical Cloud Properties at the Savannah River Site in the Southeastern US’ is included in the November 2020 issue of the journal.
Abstract: Predicting boundary layer clouds is important for the accurate modeling of pollutant dispersion. Higher resolution mesoscale models would be expected to produce better forecasts of cloud properties that affect dispersion. Using ceilometer observations, we assess the skill of two operational mesoscale models (RAMS and WRF) to forecast cloud base altitude and cloud fraction at the Savannah River Site in the southeastern US during the springtime. Verifications were performed at small spatial and temporal scales necessary for dispersion modeling. Both models were unreliable with a 50% (RAMS) and a 46% (WRF) rate of predicting clouds observed by the ceilometer which led to low cloud fraction predictions. Results indicated that WRF better predicted daytime cloud bases from convection that occurred frequently later in the period and RAMS better predicted nighttime cloud bases. Using root mean squared error (RMSE) to score the forecast periods also highlighted this diurnal dichotomy, with WRF scores better during the day and RAMS scores better at night. Analysis of forecast errors revealed divergent model cloud base biases—WRF low and RAMS high. A hybrid solution which weighs more heavily the RAMS nighttime forecasts and WRF daytime forecasts will likely provide the best prediction of cloud properties for dispersion. Doi:https://doi.org/10.3390/atmos11111202
An article by ATG Senior Scientist Brian Viner and former ATG Intern Sydney Goodlove from the SRNL Environmental Sciences and Dosimetry group, has been recently accepted to the Journal of Environmental Radioactivity. The article titled ‘Using a coupled dispersion model to estimate depletion of a tritium oxide plume by a forest’ will be included in the September issue for the journal Volumes 220–221 (2020).
Abstract: Tritium processing facilities may release tritium oxide (HTO) to the atmosphere which poses potential health risks to exposed co-located workers and to offsite individuals. Most radiological consequence analyses determine HTO dose by applying Gaussian plume models to simulate the transport of HTO. Within these models, deposition velocity is used to assess the sum of all deposition processes acting on the plume. While this may account for vegetative and soil uptake or respiration processes, it may currently lack inclusion of the complex interactions within heterogeneous forested environments. In this complex morphology, dispersion patterns are significantly altered by changing flow regimes above and below the forest canopy and by the transfer of plume material across the canopy boundary. To determine the effects of a heterogeneous forest canopy on an airborne HTO plume, a Gaussian plume model coupled with an advection-diffusion plume model was applied to estimate transport in the free atmosphere above the forest and within the forest canopy and understory. During 2012, wind speed and wind direction measurements taken at 5 heights, ranging from 2-m to 28-m, on an instrumented meteorological tower located in a loblolly pine forest at the Department of Energy (DOE) Savannah River Site (SRS), near Aiken, SC. From these measurements, model predictions were made over a full spectrum of meteorological conditions. Deposition and resuspension velocities were calculated based on the model-predicted flux of plume material across the top of the forest canopy. Additionally, net deposition velocity of the plume material was calculated as the difference between the deposition and resuspension velocities. The 1st and 5th percentile net deposition velocities were estimated to be 0.7 cm s-1 and 1.2 cm s-1, respectively. Ref. Journal of Environmental Radioactivity 220–221 (2020) 106316. Doi:https://doi.org/10.1016/j.jenvrad.2020.106316
Atmospheric Technologies Group (ATG) Meteorologist David Werth represented the lab at the annual SRNS “Teach -In” activities that reach several school systems near SRS. David provided a presentation and an interactive science demonstration on how computer modeling works at Jackson STEM Magnet Middle School in Jackson, SC and St. Mary on the Hill Catholic Middle School in Augusta, GA. SRNS “Teach-In” activities held every year during the month of February are an effort from the SRNS outreach programs to locally support and encourage STEM education with hands on experiences for students.
Atmospheric Technologies Group (ATG) meteorologists Steven Chiswell and Arelis Rivera-Giboyeaux represented the group at the 100th Annual Meeting of the American Meteorological Society (AMS) held in Boston, MA on January 12th-16th. This annual meeting brings together atmospheric scientists, operational meteorologists, broadcasters, as well as scientists in the related physical and social sciences and provides a prestigious venue to share new research, tools, and ideas that improve the field. This year Steven Chiswell chaired a session for the 36th Conference on Environmental Information Processing Technologies in which Arelis Rivera-Giboyeaux presented ATG’s meteorological quality control software.
The abstract for the presentation The Fishnet Approach of Data Quality Control at SRNL can be found at the AMS webpage https://ams.confex.com/ams/2020Annual/webprogram/Paper368484.html
Atmospheric Technologies Group (ATG) scientists David Werth and Stephen Noble represented the Savannah River National Laboratory at the American Geophysical Union (AGU) Centennial Meeting in San Francisco, CA. This meeting is the largest international Earth and Space science meeting in the world that brings together Earth and Space scientists to discuss “rapid developments in our science, new approaches to observing our Earth and beyond, the introduction of new data streams, growing demand for accessible science, the expansion of convergent science, and more” (https://www.agu.org/).Abstracts for these presentations have been attached below.
Abstract: Stephen Noble- Assessing Cloud Macrophysical Properties from an Operational Mesoscale Model
Forecasting or modeling clouds and precipitation is highly uncertain due to the lack of understanding of cloud microphysical processes. Because of their complexity, these poorly understood processes are parameterized in models. Comparisons between modeled and measured cloud macrophysical properties, such as cloud base altitude (CBA) and cloud sky fraction (CF), provide a simple but robust way to assess model skill in cloud formation and development. The numerical mesoscale model RAMS (Regional Atmospheric Modeling System) is used in operational forecasts performed at the Savannah River Site (SRS) in the southeastern US. These model runs are performed using a nested grid system with the finest grid at 1 km horizontal spacing. Modeled cloud macrophysical properties were assessed using a Vaisala CL31 ceilometer located at SRS. Initial results show model CF usually lower than detected by the ceilometer with limited instances where model CF is higher. Modeled CBA showed fair comparisons with ceilometer CBA for periods of non-convective stratus clouds. However, for more convective periods CBA was quite variable and did not always compare as well. This could be due to the difference in timing of convection in the model. However, good comparisons between model and measured CBA during times of stratus clouds provide confidence in the model ability to accurately represent CBA in these cases. This cannot be said for convective CBA. CF compared better in daily averages than 15-minute data and at later times of the year when synoptic features dominate cloud formation. Simulations covering May to November have been assessed. Research is ongoing to include data at all times of the year to provide more robust conclusions. Adding additional data or future model adjustments may improve or weaken these comparisons.
Abstract: David Werth- An Improved Method for Calculating the Lagrangian Time Scale in an Emergency Response Plume Dispersion Model
The Atmospheric Technologies Group (ATG) at the Savannah River National Laboratory in South Carolina is charged with consequence assessment in the event of the accidental airborne release of hazardous material. To accomplish this in a timely manner, ATG has developed the Puff-Plume software tool – a Gaussian model that can quickly provide expected surface concentration values and deposition values (if relevant) based on the estimated source term, the current (and forecasted) winds and turbulence, and the boundary layer stability.
To estimate the rate at which the contaminants will disperse vertically and crosswise to the wind direction, the model currently makes use of high-frequency wind measurements and several empirical approximations for stability characterization. A more explicit representation originally proposed by Taylor, however, characterizes the lateral dispersion of a Gaussian plume as a function of wind variability and the Lagrangian time scale. The latter can be calculated as either i) a function of the turbulent length scale, or as ii) a function of the Eulerian timescale (itself a function of the autocorrelation of the lateral wind fluctuations). Using both methods, we are revising the Puff-Plume model to conform to Taylor’s theory of dispersion, thereby making greater use of observed turbulence data in place of the currently parameterized values.
The new version of Puff-Plume has been validated against data from a field campaign, conducted in the vicinity of the Savannah River Site, in which a tracer was released and monitored as it traveled downwind, and ii) data from a high-resolution mesoscale simulation coupled to a dispersion model. We will discuss the results, and how the model is used in the context of emergency response.
Atmospheric Technologies Group (ATG) Meteorologist Arelis Rivera-Giboyeaux represented the lab at the Emergency Management Issues Special Interest Group (EMI SIG) in Knoxville, TN. The presentation focused on results of an evaluation of radar derived rainfall estimates against ground measurements at SRS and was presented at the DOE Meteorology Sub Committee (DMSC) meeting held on September 17th, 2019. The EMI SIG DMSC coordinates the exchange of expertise, ideas, and resources among DOE meteorologists and contractor emergency management personnel and is sponsored by the Department of Energy (DOE) Office of Plans and Policy (NA-41).
Abstract: Radar Derived Rainfall and Rain Gauge Measurements at SRS
Over the years much of the data available on rainfall amounts at the Savannah River Site has been obtained from ground level measurements made by rain gauges. These instruments have inherent errors or biases that can impact the measured rainfall totals but are assumed as ground truth for most climatological and weather applications. With the development of weather radar technologies, various methods to derive rainfall totals from radar reflectivity values have been developed and have continued to improve over the years. The Z-R relationship, which uses an exponential relationship to estimate rainfall rate based on radar reflectivity values, provides estimates of rainfall amounts for locations within a radar domain. The recently developed Multi-Radar Multi-Sensor (MRMS) dataset combines reflectivity-based estimates using the Z-R relationship with a network of gauges and other rainfall estimates to produce an enhanced set of precipitation estimates for each grid point within its domain. Comparisons were done between gauge observations and radar estimates for various SRS locations to assess whether radar derived estimates are representative of rainfall measurements at the site. Results obtained show good agreement between radar derived amounts and ground measurements, with MRMS showing stronger correlations and lower spread against gauge data. Outliers and errors observed are mostly due to problems associated to one particular rain gauge, proving that the physics behind the radar estimates and the corrections done by MRMS are correctly representing rainfall characteristics on site.
This summer SRNS welcomed approximately 140 interns to conduct research projects around the site. Among this group, two interns joined and collaborated with Atmospheric Technologies Group (ATG) to work on hydrodynamic modeling under Dr. Grace Maze, the results of which were presented on SRNL Interns’ Research Poster Session this past Wednesday, July 24th and at the ESSH/SRNL Technical Intern Seminar held on July 31st at the Applied Research Center.
Amanda Yancoskie, part of the DOE-FIU Science & Technology Workforce Development Program, developed inundation maps for potential dam failures at the Savannah River Site under the mentorship of ATG’s Grace Maze. Her project utilized the Hydrologic Engineering Center’s River Analysis System (HEC-RAS) to analyze both the Par Pond and L Lake earthen dams located on site. Her findings show under Probable Maximum Flood (PMF) conditions, Par Pond and L Lake dam failures result in flooding of all bridges and roads up to the Burtons Ferry Highway (southeast of the site, in Allendale County). Using HEC-RAS, Amanda was also able to generate water depth estimates for various points of interest along the projected flood area.
Atmospheric Technologies Group (ATG) Meteorologist Arelis Rivera-Giboyeaux represented the lab at the SRNL Science Day activities for Sanders-Clyde Elementary School in Charleston, SC. The activity held on May 30, 2019 was a joint effort between SRNS Education Outreach Program and the Charleston Promise Neighborhoods program to support STEM education with hands on activities.
Using hands-on demonstrations, Arelis focused on showing the importance of atmospheric pressure and its relationship to different weather events. Experiments showing how air pressure can be used to keep water in an upside-down glass (as shown in the attached image), demonstrating the Bernoulli principle with Bernoulli bags, and simulating how storm surge is formed in tropical systems, kept the 5th grade participants engaged and surprised.
Images courtesy of Laura Russo, SRNS Communications & Media Services
Atmospheric Technologies Group (ATG) Scientist Brian Viner was part of a contingent of SRNL scientists that attended the 12th International Conference on Tritium Science and Technology during April 2019 in Busan, South Korea. While there, he presented a poster detailing his current research titled “Evaluation of Tritium Transport in a Forested Environment.
The Atmospheric Technologies Group (ATG) attended the 25th Annual meeting of the Palmetto Chapter of the American Meteorological Society (PAMS) Allen Weber Mini-Technical Conference held on March 6th in Columbia, SC. This annual conference brings together professionals in the field of atmospheric sciences from the NWS, SCDHEC, SC Climate office, among others, to discuss topics of interest in the atmospheric and related sciences. ATG scientists presented their research conducted in diverse areas including forecasting applications of adaptive programing, development of aqueous modeling as a tool for emergency response, atmospheric dispersion modeling, and improvements to SRS meteorological monitoring tools and technologies. Additionally, two ATG scientists were elected as members of office for the local chapter for the upcoming year: Grace Maze (President), Arelis Rivera (Treasurer).
An article by ATG scientists R.J. Kurzeja, R.L. Buckley, D. W. Werth and S.R. Chiswell was recently published in the scientific journal Atmospheric Environment. In this article, they discuss a method to detect low level nuclear or chemical sources based on statistical ‘goodness of fit’ tests of downwind concentration measurements against high-resolution output from a mesoscale atmospheric transport and dispersion model. This study also provides an estimation of the probability of origin of a given concentration signature. The technique was applied to data from the Comprehensive Test Ban Treaty (CTBT) collection site in Russia after the underground nuclear test held in North Korea on February 12, 2013. Preliminary results from this evaluation suggest that radioxenon was likely emitted from the nuclear test at various times during the month of April 2013. Further research on the extension of the model to different datasets, and evaluation of the uncertainty of estimated probabilities of origin are still needed to expand the capabilities of this method.
The full article can be accessed online using the link below:
Every year the Savannah River Site receives approximately a hundred interns giving them the opportunity to learn, develop their skills and contribute with their ideas and new perspectives to the work done at SRS and SRNL. This year Sydney Sanders joins ATG to work with Dr. Grace Maze in a project that will generate new software that has the potential to serve as a national asset for emergency response. She will focus on developing input files for an aqueous release dispersion model that is currently under development. Sydney is currently a senior of the Civil Engineering program at the University of South Carolina (USC) – Columbia. Coming from a family of engineers, she plans to continue to pursue a graduate degree in the field of Civil and/or Resource Engineering. Her favorite part of civil engineering is the number of applications it has and the many areas of specialization found within the field.
For more information on internship opportunities and university partnerships available with ATG and SRNL, please visit the link below.
An article by ATG’s Senior Scientist Dr. Brian Viner, in collaboration with scientists from the USDA Forest Service Savannah River, Ohio State University (College of Health Sciences), and the University of Georgia School of Public Health, has been accepted for publication in the Journal of Environmental Radioactivity. The article is titled: Predicted cumulative dose to firefighters and the offsite public from natural and anthropogenic radionuclides in smoke from wildland fires at the Savannah River Site, South Carolina USA. More details about the study and its findings can be found in the abstract below.
Abstract: The contaminated ground surface at Savannah River Site (SRS) is a result of the decades of work that has been performed maintaining the country’s nuclear stockpile and performing research and development on nuclear materials. The volatilization of radionuclides during wildfire results in airborne particles that are dispersed within the smoke plume and may result in doses to downwind firefighters and the public. To better understand the risk that these smoke plumes present, we have characterized four regions at SRS in terms of their fuel characteristics and radiological contamination on the ground. Combined with general meteorological conditions describing typical and extreme burn conditions, we have simulated potential fires in these regions and predicted the potential radiological dose that could be received by firefighting personnel and the public surrounding the SRS. In all cases, the predicted cumulative dose was a small percent of the US Department of Energy regulatory limit (0.25 mSv). These predictions were conservative and assumed that firefighters would be exposed for the duration of their shift and the public would be exposed for the entire day over the duration of the burn. Realistically, firefighters routinely rotate off the firefront during their shift and the public would likely remain indoors much of the day. However, we show that even under worst-case conditions the regulatory limits are not exceeded. We can infer that the risks associated with wildfires would not be expected to cause cumulative doses above the level of concern to either responding personnel or the offsite public.
SRNL is dedicated to maintaining the scientific and technological vitality of the lab, fostering creativity and enhancing core lab capabilities through the Laboratory Directed Research and Development (LDRD) initiative. Each year, this program provides funding for innovative research projects in various areas that range from National Security to Environmental Stewardship. The very competitive selection process begins with a ‘pitch’ presentation of the proposed research, followed by a written proposal submission to a committee that selects projects to be funded under each of the areas supported by LDRD. In previous years, ATG scientists have been active participants of this program; and this year was no exception with three research projects presented at the End of the Year Review and Poster Session held at SRS on October 3, 2017.
The project titled Advanced Cloud Forecasting for Solar Energy’s Impact on Grid Modernization was presented by Dr. David Werth. This project studies the impacts of short-term variability in solar irradiance on solar power production. A comprehensive solar monitoring station was established to measure direct and indirect solar irradiance, infrared irradiance, and output from an adjacent solar panel. These data were used to study the impact of cloud type and aerosols on local solar irradiance and solar power production, and to evaluate a method to forecast the amount and variability of daily solar irradiance by using analog weather predictions, i.e. looking at weather conditions from the past to predict short term future weather conditions. Results show good agreement between analog forecasts and observations. Based on this project, ATG currently has the capability to create daily solar forecasts using the analog technique.
Dr. Robert Kurzeja, presented the project Evaluation and Uncertainty of a New Method to Detect Suspected Nuclear and WMD Activity. This study focused on assessing the ability to detect signals from Weapons of Mass Destruction (WMD) and nuclear activity using a time series of chemical or radiological measurements, and to calculate probability of origin of the signal in question using Bayesian statistics. Testing of this method with 2013 data from a Comprehensive Test Ban Treaty site showed small uncertainty values in the calculated probability of origin for the suspect activity. This evaluation also proved that the method remains reliable under conditions when chemical signals are weak, hence proving to be an important method to detect concealed nuclear activity.
Finally, Dr. Robert Buckley discussed Advanced Atmospheric Modeling Techniques for Non-Proliferation Applications. In an extension to work done the previous year (also under LDRD), this project evaluates atmospheric transport models and compares 3 ensemble techniques: standard ensemble, adaptive programming, and data assimilation (Ensemble Kalman Filter), on a small spatial scale and complex terrain. Field data collected during field tracer experiments conducted at Diablo Canyon, CA were used to evaluate the different techniques. Results of ensemble model against observations show improvement in downwind concentration estimations using the Kalman Filter and Adaptive Programming ensemble techniques. These results demonstrate the importance of adapting model physics to specific location and time, and assimilating local data into the simulation to obtain better transport accuracy.
New and exciting projects led by, or in collaboration with ATG members were also awarded funding for this upcoming year (2018) during the presentation.
This summer SRNL welcomed approximately 140 interns to conduct research projects around the site. Among this group, 3 interns joined and collaborated with Atmospheric Technologies Group (ATG) to work on exciting projects, the results of which were presented on SRNL Interns’ Research Poster Session this past Thursday, July 26th at the Applied Research Center.
Michael Stewart, from the University of South Carolina, studied solar power generation, under the guidance of ATG’s David Werth. His research examined the intermittency of power output and the contribution of direct and indirect radiation to photovoltaic (PV) power generation. Results suggest that although direct radiation is a major contributor to power generation, indirect radiation is also significant. Additionally, a large variation in PV output over a short time scale was observed, as well as significant spatial variation across Savannah River Site. Future research will examine a bimodal distribution of power generation against indirect and direct radiation that was observed during this study.
Nicolet Chovancak, also from the University of South Carolina, focused on our STREAMII aqueous model under the mentorship of Grace Maze (ATG) and Vidya Samadi (USC). Her project, titled Uncertainty Analysis in Streamflow Data, looked at the change in transport and fate of materials given the uncertainty in the monthly stream flow values currently used by the model. Her findings show that the variation in transport times and maximum concentration is not large when minimum, average, and maximum flow values are compared.
Additionally, Beth Mitchell from Winthrop University – working for her second year as intern with the SRNL Chief Information Office and Scientific Computing - continued her work on developing and updating the ATG webpage. In 2016, under the mentorship of Cory Herbst and Andrew Kail, Beth had created the ATG business page that is currently active. This year, her efforts focused on updating ATG’s weather web page and forecast input pages. The web page Beth created is expected to go live as the new official weather web page soon!
It is with very heavy hearts that we announce the passing of our esteemed friend and colleague Matt J. Parker. Our group, and the entire meteorological enterprise, has had a sudden and big loss. Below is a tribute to Matt given by ATG Group Manager Chuck Hunter, during the Funeral Service on March 24, 2017:
It’s my honor and privilege to speak to the life of Matt Parker on behalf of his work family – the Atmospheric Technologies group at SRNL.
I first met Matt in the fall of 1988. He was a grad student at North Carolina State University at the time, and had come down for several weeks with a group from State to participate in a DOE-sponsored nighttime field data collection experiment that was being coordinated by Dr. Allen Weber of our group. We were impressed by Matt and so we hired him the following year after completing his Master’s degree.
Dr. Weber was a former professor at NC State, and he always took a very nurturing approach with young scientists – mentoring them with their work and encouraging them to become active in our professional society, the American Meteorological Society. So, as the new young scientist in our group, Allen naturally took Matt under his wing. And as many of us here today would later come to appreciate, this experience would have a very profound and life-long impact on Matt. When it was our turn, we all very much appreciated Allen’s advice and wise counsel, but mostly we would just nod with a bit of ambivalence at Allen’s not so subtle prodding that, first: we become active in the Society and, and then, more importantly, work towards obtaining the professional status of Certified Consulting Meteorologist.
But not Matt Parker! With Allen, Matt was all in. Both feet.
Throughout this journey, he enthusiastically took his mentor to heart when it came to serving the young scientist – whether it be in his AMS activities or in his work with us at SRNL, it was vitally important to Matt to reach out to the students, the interns, the new hires to provide advice and counsel, cajole them to become AMS certified, guide them through their work without an air of condescension, to readily offer praise and encouragement.
Family was always most important to Matt – both his personal family and his professional family. And even though Matt earned wonderful individual accolades, I know personally through my many, often lengthy, conversations with him, that as far as his professional life, his work family came first. Certainly, he took great pride in his own achievements, but part of his motivation to pursue these goals was to contribute to the greater good of our group through greater recognition and creating contacts that would help our team develop new business.
He was the consummate teammate, willing to give selflessly to achieve our common goals.Whether he was just a contributor to the project or leading the project, you could count on Matt to give his full effort, reach out to pull in the right set of skills, then work together to achieve the desired result. Always with diligence and excellence.
Matt firmly believed that we were the best meteorology group throughout the Department of Energy or anywhere else for that matter. Naturally, I believe that to be that case as well.
But whatever our group’s status may be, it’s in no small part because of our world class meteorological measurements and observations program, a program that thrived under Matt’s technical expertise and leadership, and more importantly how effective he was in nurturing the small cadre of engineering specialists that turned his ideas into reality in the field.
Because of his caring relationship with his specialists – and, his ability to explain technical details in ways that led to the job at hand being thoroughly understood, there are no bigger fans of Matt Parker than the three guys that supported Matt over the years. Without fail, I would get e-mail from Matt praising their work after a major job was completed.
Our work group at SRNL has always been close, and Matt was a beloved member of our workplace family. We’ve now lost a close family member and it hurts. And although it sounds clichéd, we’re determined to pull together to carry on his work, our work, because we know Matt would have wanted it this way….
March 24, 2017
Reid Memorial Presbyterian Church
Founded in 1919, AMS is the nation’s premier scientific and professional organization promoting and disseminating information about the atmospheric, oceanic and hydrologic sciences. The membership includes scientists, researchers, educators, broadcast meteorologists, students, and other professionals in the fields of weather, water and climate. As president, he will represent the Society’s 13,000 members (both domestically and abroad), and will lead the AMS Council, the governing body of the organization. The president also determines the theme for the Annual Meeting. Parker will preside over the 2018 event in Austin, TX under the theme ‘Transforming Communication in the Weather, Water, and Climate Enterprise: Focusing on Challenges Facing Our Sciences’.
Parker plans to use his leadership position to provide outreach to industry, academia and the public; and to enhance partnerships with other countries to share measurement and forecast data. “Relationships with colleagues abroad are critical for ensuring sharing of measurement and modeling data, as well as enhancing ‘universal’ professional development principles. Weather and climate know no geopolitical boundaries.” - He adds.
The official SRNL Press Release can be accessed here:
ATG members, David Werth and Robert Buckley, recently submitted an article on emission signals from nuclear detonations. The article titled ‘Characterizing the detectability of emission signals from North Korean nuclear detonation’ has now been accepted for publication in the Journal of Environmental Radioactivity Volumes 169-170, pages 214 – 220.
Abstract: The detectability of emission sources, defined by a low-level of mixing with other sources, was estimated for various locations surrounding the Sea of Japan, including a site within North Korea. A high-resolution meteorological model coupled to a dispersion model was used to simulate plume dynamics for four periods, and two metrics of airborne plume mixing were calculated for each source. While emissions from several known sources in this area tended to blend with others while dispersing downwind, the North Korean plume often remained relatively distinct, thereby making it potentially easier to unambiguously ‘backtrack’ it to its source. Ref. Journal of Environmental Radioactivity 169-170 (2017) 214e220. Doi: 10.1016/j.jenvrad.2016.12.002
Intermediate Time-Scale Response of Atmospheric CO2 following Prescribed Fire in a Longleaf Pine Forest by B. Viner, M. Parker, G. Maze, P. Varnadoe, M. LeClerc, G. Starr, D. Aubrey, G. Zhang, and H. Duarte was published in the Journal of Geophysical Research: Biogeosciences (online)
Abstract - Fire plays an essential role in maintaining the structure and function of longleaf pine ecosystems. While the effects of fire on carbon cycle have been measured in previous studies for short periods during a burn and for multi-year periods following the burn, information on how carbon cycle is influenced by such changes over the span of a few weeks to months has yet to be quantified. We have analyzed high-frequency measurements of CO2 concentration and flux, as well as associated micrometeorological variables, at three levels of the tall Aiken AmeriFlux tower during and after a prescribed burn. Measurements of the CO2 concentration and vertical fluxes were examined as well as calculated net ecosystem exchange (NEE) for periods prior to and after the burn. Large spikes in both CO2 concentration and CO2 flux during the fire and increases in atmospheric CO2 concentration and reduced CO2 flux were observed for several weeks following the burn, particularly below the forest canopy. Both CO2 measurements and NEE were found to return to their pre-burn states within 60-90 days following the burn when no statistical significance was found between pre-burn and post-burn NEE. This study examines the micrometeorological conditions during a low-intensity prescribed burn and its short-term effects on local CO2 dynamics in a forested environment by identifying observable impacts on local measurements of atmospheric CO2 concentration and fluxes. Ref: Journal of Geophysical Research: Biogeosciences DOI:10.1002/2016JG003351
Matt Parker was the featured speaker at a seminar sponsored by the Department of Chemistry and Physics at Augusta University in Augusta, GA. Matt's talk, 'Atmospheric Research at the Savannah River National Laboratory', touched on the wide variety of applied studies conducted by ATG related to emergency response, long-range atmospheric transport, climate change impacts and renewable wind and solar energy, and included discussion of some of the advanced modeling techniques and innovative meteorological monitoring technologies currently being developed. Matt also discussed the ties between weather, climate and human health as well as his work as the President Elect of the American Meteorological Society. Comments on career development for students were also covered.
The paper ‘On dispersion above a forest – measurements and methods’ by B. B. Hicks, C. H. Hunter, and A. H. Weber was published in the Journal of the Air and Waste Management Association (Aug 2016).
Abstract - High frequency (10 hz) measurements over a mixed conifer/deciduous forest at the Savannah River Site in South Carolina using sonic anemometry reveal that on-site and real-time measurements of the velocity component standard deviations, σv and σw, are preferred for dispersion modeling. Such data are now easily accessible, from the outputs of cost-effective and rugged sonic anemometers. The data streams from these devices allow improvements to conventional methodologies for dispersion modeling. In particular, extrapolation of basic input data from a nearby location to the site of the actual release can be facilitated. In this regard reliance on the velocity statistics σv and σw appears to be preferred to the conventional σθ and σϕ. In the forest situations addressed here, the uncertainties introduced by extrapolating initializing properties (u, θ, σθ, and σϕ, or alternatively, σv and σw) from some location of actual measurement to some nearby location where an actual release occurs are similar to those associated with the spread of the plume itself and must be considered in any prediction of the likelihood of downwind concentration (exposure) exceeding some critical value, i.e., a regulatory standard. Consideration of plume expansion factors related to meander will not necessarily cause predicted downwind maxima within a particular plume to be decreased; however, the probability of exposure to this maximum value at any particular location will be reduced. Three-component sonic anemometers are affordable and reliable, and are now becoming a standard for meteorological monitoring programs subject to regulatory oversight. The time has come for regulatory agencies and the applied dispersion community to replace the traditional discrete sets of dispersion coefficients based on Pasquill stability by the direct input of measured turbulence data. Ref.- J Air Waste Manag Assoc. 2016 Aug;66(8):768-85. doi: 10.1080/10962247.2016.1178189.
Brian Viner and Sydney Goodlove (ATG summer intern) presented a poster at the AMS 32nd Conference on Agricultural and Forest Meteorology entitled ‘Using Atmosphere-Forest Flux Measurements to Examine Potential for Reduced Downwind Dose ‘(poster). Wind and moisture flux data from ATG’s forest flux tower (the Aiken Ameriflux Tower) are being used as input to coupled Gaussian dispersion model (above canopy) and a 2-D advection diffusion model (within canopy) to characterize the fate of an airborne plume of radioactive tritium oxide (H3O) as it interacts with a forested surface. For a short-term release (a few hours), we expect this interaction will lead to an effective removal of material from the airborne plume, resulting in lower concentration and radiological dose to the affected public than would otherwise be obtained from standard models used in nuclear facility safety analysis. The goal is to define an ‘effective’ deposition velocity to account for these interaction in the standard models.
Plume characteristics above and within the forest were evaluated 10 km from the release point. A greater fraction of the plume was predicted to mix into the forest under very stable conditions (E/F Stability) or very unstable conditions (A/B Stability). Less mixing was predicted for near-neutral conditions (C/D Stability). Increased mixing during the day is attributed to increased turbulence during the day; the vertical convective turbulence in addition to the mechanical turbulence at the forest top combine to mix a greater fraction of the plume downward. In stable conditions, a narrow, highly concentrated plume constrained near the forest top creates a larger gradient between the atmosphere and forest airspace, increasing the downward flux of the plume into the forest. The next stage of this project will be to analyze the rates of mixing into the forest under these conditions to determine the appropriate estimates deposition velocity. This work is being funded primarily from a Nuclear Safety Research and Development Grant from the National Nuclear Security Administration (NNSA).
David Werth presented the paper ‘Novel Ensemble Atmospheric Modeling Techniques for the Simulation of Large-Scale Dispersion’ at the 20th George Mason University Conference on Atmospheric Transport and Dispersion Modeling. Abstract - Tracer release simulations have historically been performed using a single high-resolution meteorological simulation, making use of both 1) model parameters estimated by the user, and 2) observations from weather stations. Our knowledge of the initial atmospheric state is often guided by a small number of weather observations, while model ‘free’ parameters are often poorly constrained. Thus, a single model solution can be considered to be only one possible representation of the meteorology.
Ensemble modeling - running multiple simulations with various plausible values of such inputs - is used to allow for uncertainty in poorly understood model parameters or in sparse weather observations. This standard ensemble approach provides a range of possible model solutions, but may still experience systematic model errors. Our current research explores alternatives to the standard ensemble approach through the development of two novel methods: (1) minimizing model error through adaptive (physics-based) programming techniques and (2) reducing ensemble variance by applying an ensemble Kalman filter to optimize the assimilation of observational data. We will show that substantial improvement in transport accuracy can be achieved when a model is adapted to a particular location and time.
Chuck Hunter attended a bi-monthly meeting of the SRS Citizens Advisory Board in Savannah, GA to present an invited talk ‘Assessing Public Health Risks from SRS Air Emissions’. In a 2014 report, the Agency for Toxic Substance and Disease Registry concluded that radiological and most of the toxic air pollutant emissions from SRS facilities were unlikely to pose adverse health effects among members of the public. Nonetheless, the report identified eight toxic air pollutants for which an evaluation could not be completed due to insufficient data. The presentation to the CAB summarized results from a followup modeling study that examined an additional 10 years of emissions data for each of these eight chemicals, pursuant to ASTDR recommendations. In all cases, the modeling results indicated that it would be highly unlikely for the public to be exposed to concentrations exceeding either a concentration reference standard above which a non-cancer health effect could be expected, or producing an additional carcinogenic risk greater than one in 10,000.
Dr. Allen Weber was remembered for his long-standing contributions to the Chapter and founder of this highly successful annual event. Allen worked in ATG for more than 30 years and was integral to forging ATG’s long-standing mission.