This research seeks to improve understanding of the physics of convergent boundary zones (CBZ), focusing on the neutral to stable boundary layer, within which CBZ's and convective initiation (CI) are poorly understood. Two primary and closely related objectives include comprehensive investigations of: 1. CBZ kinematics and CI during the Afternoon to Evening Transition (AET); 2. Characteristics of CBZs (e.g., bores, gravity waves) within the stable (nocturnal) boundary layer and their impact on cloud formation and CI.

The project involves data collection, analysis, and numerical modeling activities. A major component of this research will be accomplished by deploying a mobile X-band dual polarization radar (MAX) and a mobile profiling system (MIPS) within a meso-Gamma-scale mesonet when CBZ's are anticipated from mid-afternoon to evening. The MIPS will be embedded within one lobe of a high-resolution dual Doppler network (18 km baseline), formed by the MAX and a fixed site C-band radar. Additional surface observations will include fixed and mobile platforms. The research team also plans to use data from the Department of Energy's Atmospheric Radiation Measurement-Southern Great Plains (ARM SGP) profiling site in Oklahoma, combined with multiple Doppler radar observations from a new network of radars installed around the ARM SGP central site. Numerical simulations, designed to complement the observations, will provide additional details on boundary layer and CI processes inferred from the observations. Results of this project will be compared to International H2O project (and other) studies, which have shown a highly 3-D structure of CBZ's within deep convective boundary layers, due to interactions of large eddies with cold front and drylines.

Intellectual merit. This project will provide considerable advances in our understanding of the physics of CBZ's and CI by examining these phenomena in a parameter space (neutral to stable) that has not been comprehensively explored in previous studies. The unique feature of this project is its emphasis on the AET and nocturnal boundary layer (neutral to stable conditions). Since the MAX and MIPS are mobile platforms, they will be utilized in a preconfigured dual Doppler network when CBZs are expected during the mid-afternoon to evening time periods. This flexibility will provide comprehensive datasets at low cost and low risk when compared to limited duration field campaigns. In addition, data from the ARM SGP site (northern OK) will be monitored and analyzed similarly. Both experimental locations will provide comprehensive data from wind profilers, vertically pointing radars, balloon soundings, ground-based IR/microwave profilers, and multiple Doppler radar arrays.

Broader impacts. Improved forecasting of CI, lightning, severe weather (tornadoes), and boundary-layer atmosphere transports (air quality) represent significant societal benefits of this research. The comprehensive nature of measurements (and the 24/7 capability) will increase probability of serendipitous scientific discoveries. The data collected at the Huntsville and Lamont (OK) sites, and the University of Alabama in Huntsville (UAH) instrumentation, will be utilized extensively in PI's (i) two graduate level courses, Boundary Layer Meteorology and Ground-Based Remote Sensing; and (ii) a book Ground-Based Remote Sensing. Two UAH graduate students and one postdoctoral associate will be actively engaged in all aspects of the field campaign and subsequent modeling activities. The UAH platforms will be made available to other UAH students who have research interests in related topics. The project will support and utilize MIPS and MAX, the former of which has been utilized in numerous scientific projects over the last decade. The datasets will contribute to other disciplines, such as mesoscale/microscale structure of fronts, gravity waves in the severe storms environment, boundary layer process, and properties of biological flyers.

National Science Foundation (NSF)
Division of Atmospheric and Geospace Sciences (AGS)
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A. Gannet Hallar
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University of Alabama in Huntsville
United States
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