MM5 simulations of the 4-7 August SCOS97-NARSTO ozone episode in the SoCAB showed that a relative... more MM5 simulations of the 4-7 August SCOS97-NARSTO ozone episode in the SoCAB showed that a relatively rare easterly upper-level background flow influenced surface wind flow directions at in-land sites. An inland-moving surface convergence zone resulted where the offshore background flow met an inland moving westerly (sea breeze plus thermal upslope) onshore flow. Maximum inland penetration of the zone was to the San Gabriel Mountains, where it produced peak observed ozone concentrations. MM5 reproduced the main qualitative features of the evolution of the diurnal sea breeze cycle, as it reproduced the opposing easterly flow, inland movement of the sea breeze front, and retreat of the land breeze front. The accuracy of predicted surface winds and temperatures were improved by modifications of MM5 and/or its input parameters, e.g., by use of the PSU MBLI scheme, analysis nudging with NCAR/NCEP model output, accurate specification of deep-soil temperature, observational nudging with SCOS97-NARSTO surface and upper level winds and temperatures, and use of updated urban land-use patterns.
This thesis investigates climatic variability of the winter season in the southern Appalachian Mo... more This thesis investigates climatic variability of the winter season in the southern Appalachian Mountains and identifies the associated large-scale atmospheric forcing patterns. Recognized as an anomalous region regarding climate change, this study identifies long-term trends and variation of temperature and snowfall during climatological winter (DJF) from 1910 to 2017. The identification of several teleconnection patterns, namely ENSO, NAO, and PDO, allow for further understanding of how this region has remained a climatic anomaly. Results of this study indicate that the southern Appalachian Mountains have experienced a statistically significant long-term cooling trend since the early 20th century, with recent decades suggesting a reversal of this cooling. Snowfall is characterized by high interannual variability, with the 1960s and 1970s producing anomalously high amounts of snowfall. Several atmospheric forcing couplings are identified that align with anomalous conditions in the region. Most notably, negative temperature anomalies and higher snowfall amounts are frequently found during moderate El Niño and negative NAO seasons, with the opposite being true during strong La Niña and positive NAO winters. The v influence of these teleconnection patterns is spatially dependent, with areas east of the Blue Ridge Escarpment highly dependent on the phase of ENSO, whereas higher elevations and western slopes favor the NAO. The identification of these pattern couplings is critical to not only improving understanding of the anomalous climate of the southern Appalachian Mountains but also in enhancing seasonal forecasting and predicting future climate change in the region. vii since my time at UNCA, I will always value the community building experiences that the university provided me. Following my time at UNCA, I envisioned remaining in the university environment, where important intellectual conversations regarding the issues of today are discussed freely. This ultimately led me to Appalachian State, where the transition from a humanities-based undergraduate experience to a science-based graduate program was difficult at times, but I truly believe that my multidisciplinary background enhanced my skills as a researcher. Dr. Baker Perry was an encouraging force in my academic pursuits in the Geography program and presented me with multiple opportunities to grow as a researcher and broaden the reach of my work by encouraging me to present my work both regionally and internationally. Along with presenting at the Annual Celebration of Student Research at Appalachian, I have also presented the findings of my work at the Eastern Snow Conference in Ottawa, Canada. Dr. Perry has provided a helpful hand in guiding my research and has been a constructive critic of every academic paper, presentation, and iteration of my thesis. My graduate experience at Appalachian State has been transformative, both academically and personally, allowing me to pursue opportunities and experiences that would not have been possible elsewhere. My friends within the program have also shaped my experience at Appalachian State. From late night edit sessions on final papers to finishing comprehensive exams, my peers in the program were always there when I needed support. Lauren Andersen, Abie Bonevac, Burke McDade, and Zach Osborne made completing R-modules, working in the Viz-lab, and doing academic research a fun and worthwhile experience. I will forever appreciate their willingness to sit through presentation practice sessions or provide last minute critiques of viii conference abstracts and final papers. I cannot thank them enough for their friendship and encouragement during the final few months of my time at Appalachian. Lastly, I want to thank my committee members for their guidance and support in completing my thesis. They were always available to lend a helping hand in understanding complex climatic patterns, performing data analysis, and providing critical feedback. As with any thesis or academic work, the availability of data is crucial for performing meaningful analysis. We are fortunate in climate studies to have a wide range of climate databases and I would like to acknowledge several organizations that provide these data to the public. Namely, I would like to recognize the Southeast Regional Climate Center and the sister climate centers across the country for providing climate interpretation tools to citizens across the United States. I would also like to thank the National Center for Environmental Information, National Center for Atmospheric Research, and the Earth System Research Laboratory for providing the necessary climatic data needed to complete this study. The analysis from these datasets allowed me to present my results both regionally and internationally, which not have been possible without funding from the Department of Geography and Planning as well as the Office of Student Research.
The error in mesoscale model forecasts on the West Coast of the United States often depends stron... more The error in mesoscale model forecasts on the West Coast of the United States often depends strongly on the quality of the synoptic scale forecast. Kuypers (2000) demonstrated that small differences in synoptic scale initial analyses due to different random samples of the large scale structure are sufficient to cause large errors in the mesoscale forecast. This dependence of the mesoscale on the synoptic scale is often mirrored in statements like, A good mesoscale forecast requires a good synoptic scale forecast. The method by which a good synoptic scale forecast is achieved is the subject of numerous efforts at improving the observations over the Pacific through targeting of observations.
During PACJET 2001, an intense extratropical cyclone rapidly developed off the Southern Californi... more During PACJET 2001, an intense extratropical cyclone rapidly developed off the Southern California coast and produced substantial rainfall as it interacted with coastal topography. Operational models tended to misplace the position and underforecast the intensity of the storm, which was due in part to a lack of observations over the cyclogenesis region off the coast of Southern California. PACJET made dropsonde and other insitu observations in the area, which were available for data assimilation tests using the Navy's COAMPS model.
In late October 2012, Hurricane Sandy tracked along the eastern U.S. coastline and made landfall ... more In late October 2012, Hurricane Sandy tracked along the eastern U.S. coastline and made landfall over New Jersey after turning sharply northwest and becoming posttropical while interacting with a complex upperlevel low pressure system that had brought cold air into the Appalachian region. The cold air, intensified by the extreme low pressure tracking just north of the region, combined with deep moisture and topographically enhanced ascent to produce an unusual and high-impact early season northwest flow snow (NWFS) that has no analog in recent history. This paper investigates the importance of the synoptic-scale pattern, forcing mechanisms, moisture characteristics (content, depth, and likely sources), and low-level winds, as well as the evolution of some of these features compared to more typical NWFS events in the southern Appalachian Mountains. Several other aspects of the Sandy snowfall event are investigated, including low-level stability and mountain wave formation as manifested in vertical profiles and radar observations. The importance to operational forecasters of recognizing and understanding these factors and differences from more common NWFS events is also discussed.
1 Appalachian State University, Boone, NC; 2 University of North Carolina at Asheville, Asheville... more 1 Appalachian State University, Boone, NC; 2 University of North Carolina at Asheville, Asheville, NC; 3 North Carolina State University, Raleigh, NC; 4 National Weather Service, Greer, SC; 5 National Weather Service, Blacksburg, VA. ... Atmospheric Influences on ...
Rainfall observations in the Pigeon River basin of the southern Appalachian Mountains over a 5-yr... more Rainfall observations in the Pigeon River basin of the southern Appalachian Mountains over a 5-yr period (2009–14) are examined to investigate the synoptic patterns responsible for downstream flooding events as observed near Knoxville, Tennessee, and Asheville, North Carolina. The study is designed to address the hypothesis that atmospheric rivers (ARs) are primarily responsible for the highest accumulation periods observed by the gauge network and that these periods correspond to events having a societal hazard (flooding). The upper 2.5% (extreme) and middle 33% (normal) rainfall events flagged using the gauge network observations showed that half of the heaviest rainfall cases were associated with an AR. Of those extreme events having an AR influence, over 73% had a societal hazard defined as minor-to-major flooding at the USGS river gauge located in Newport, Tennessee, or flooding observations for locations near the Tennessee and North Carolina border reported in the Storm Data p...
The challenge of simulating a realistic evolution of optical turbulence in the stable, free atmos... more The challenge of simulating a realistic evolution of optical turbulence in the stable, free atmosphere, even under the conditions of a strong jet-streak, by a state-of-the-art mesoscale model has been documented by Walters and Miller (1999). In the case presented, Walters and Miller (1999) showed that a modification of the shear and buoyancy contributions to the simulated turbulent kinetic energy (TKE) using a Mellor-Yamada 2.5 parameterization (Mellor and Yamada 1974, 1982; Yamada 1975) resulted in model predictions which had more realistic TKE magnitudes when compared to radar, balloon, and wind tunnel measurements. What has yet to be investigated is the sensitivity of the modified version of the Bougeault and Lacarrere (1989) mixing length parameterization to initial conditions and to model vertical and horizontal resolution. The sensitivity of simulated TKE will be the focus of this study under the conditions of low and moderate turbulence which occurred with the approach of a c...
Two heavy rainfall events occurring in early 2020 brought flooding, flash flooding, strong winds ... more Two heavy rainfall events occurring in early 2020 brought flooding, flash flooding, strong winds and tornadoes to the southern Appalachian Mountains. The atmospheric river-influenced events qualified as extreme (top 2.5%) rain events in the archives of two research-grade rain gauge networks located in two different river basins. The earlier event of 5–7 February 2020 was an event of longer duration that caused significant flooding in close proximity to the mountains and had the higher total accumulation observed by the two gauge networks, compared to the later event of 12–13 April 2020. However, its associated downstream flooding response and number of landslides (two) were muted compared to the April event (21). The purpose of this study is to understand differences in the surface response of the two events, primarily by examining the large-scale weather pattern and available space-based observations. Both storms were preceded by anticyclonic Rossby wave breaking events that led to...
The ability to forecast turbulence using mesoscale atmospheric models has proven challenging beca... more The ability to forecast turbulence using mesoscale atmospheric models has proven challenging because of the complexities of the dynamic processes responsible for its genesis. The necessity of turbulence forecasts has become clear for applications within the aviation industry, the astronomical community, and for effective laserbased defense programs. The challenge of utilizing today’s mesoscale models for generating deterministic turbulence forecasts has been documented by Walters and Miller (1999). In the case presented, Walters and Miller (1999) showed that a modification of the shear and buoyancy contributions to the simulated turbulent kinetic energy (TKE) using a Mellor-Yamada 2.5 parameterization (Mellor and Yamada 1982; Yamada 1975) resulted in model predictions which had more realistic TKE magnitudes when compared to radar, balloon, and wind tunnel measurements. Walters and Miller (1999) and Miller and Walters (2001) demonstrated a methodology for computing optical turbulence...
Precipitation forecasting in the mountainous region of Western North Carolina, Upstate South Caro... more Precipitation forecasting in the mountainous region of Western North Carolina, Upstate South Carolina, and Northeast Georgia is difficult due to the surrounding topographic features (Figure 1). The numerous microclimates in the region resulting from the mountains create challenges for environmental models to accurately predict the evolution of weather systems as they enter the region. This is particularly true during the cool weather season (Keeter et al. 1993).
Public reporting burden for the collection of information is estimated to average 1 hour per resp... more Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.
The long term goal of this project is to determine the mesoscale atmospheric predictability and h... more The long term goal of this project is to determine the mesoscale atmospheric predictability and how it relates to synoptic scale uncertainty due to sampling and data assimilation of incomplete samples on the larger scale.
The long term goal of this project is to determine the mesoscale atmospheric predictability and h... more The long term goal of this project is to determine the mesoscale atmospheric predictability and how it relates to synoptic scale uncertainty due to sampling and data assimilation of incomplete samples on the larger scale.
Well-managed forests and woodlands are a renewable resource, producing essential raw material wit... more Well-managed forests and woodlands are a renewable resource, producing essential raw material with minimum waste and energy use. Rich in habitat and species diversity, forests may contribute to increased ecosystem stability. They can absorb the effects of unwanted deposition and other disturbances and protect neighbouring ecosystems by maintaining stable nutrient and energy cycles and by preventing soil degradation and erosion. They provide much-needed recreation and their continued existence contributes to stabilizing rural communities Forests are managed for timber production and species, habitat and process conservation. A subtle shift from multiple-use management to ecosystems management is being observed and the new ecological perspective of multifunctional forest management is based on the principles of ecosystem diversity, stability and elasticity, and the dynamic equilibrium of primary and secondary production. Making full use of new technology is one of the challenges facing forest management today. Resource information must be obtained with a limited budget. This requires better timing of resource assessment activities and improved use of multiple data sources. Sound ecosystems management, like any other management activity, relies on effective forecasting and operational control. The aim of the book series Managing Forest Ecosystems is to present state-ofthe-art research results relating to the practice of forest management. Contributions are solicited from prominent authors. Each reference book, monograph or proceedings volume will be focused to deal with a specifi c context. Typical issues of the series are: resource assessment techniques, evaluating sustainability for evenaged and uneven-aged forests, multi-objective management, predicting forest development, optimizing forest management, biodiversity management and monitoring, risk assessment and economic analysis.
The challenge of simulating a realistic evolution of optical turbulence in the stable, free atmos... more The challenge of simulating a realistic evolution of optical turbulence in the stable, free atmosphere, even under the conditions of a strong jet-streak, by a state-of-the-art mesoscale model has been documented by Walters and Miller (1999). In the case presented, Walters and Miller (1999) showed that a modification of the shear and buoyancy contributions to the simulated turbulent kinetic energy (TKE) using a Mellor-Yamada 2.5 parameterization (Mellor and Yamada 1974, 1982; Yamada 1975) resulted in model predictions which had more realistic TKE magnitudes when compared to radar, balloon, and wind tunnel measurements. What has yet to be investigated is the sensitivity of the modified version of the Bougeault and Lacarrere (1989) mixing length parameterization to initial conditions and to model vertical and horizontal resolution. The sensitivity of simulated TKE will be the focus of this study under the conditions of low and moderate turbulence which occurred with the approach of a c...
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