Five Year Comparison of Mixing Height Determinations at the Savannah River Site
- Savannah River National Laboratory (SRNL), Aiken, SC (United States)
- Savannah River National Laboratory (SRNL), Aiken, SC (United States). Atmospheric Technologies Group
- Medical Univ. of South Carolina, Charleston, SC (United States)
Air quality dispersion modeling is performed for the Savannah River Site (SRS) to demonstrate compliance with applicable regulations. The AMS/EPA Regulatory Model (AERMOD) modeling system is an EPA recommended model for air quality applications with a data preprocessor (AERMET) to incorporate meteorological data collected on site. AERMET parameterizes or calculates meteorological variables that are not directly measured onsite. One of the parameters estimated by AERMET is the atmospheric mixing height. While the mixing height is not currently a measurement input into AERMET, SRS has the capability to measure the local mixing height. The Savannah River National Laboratory (SRNL) operates a Vaisala CL31 Lidar Ceilometer which estimates mixing height from aerosol backscatter. This study compares the parameterized mixing height from AERMET to the ceilometer estimated mixing height for the current regulatory period at SRS incorporating data from 2015-2019. Results from this study showed the average daily minimum values (morning) from AERMET were an order of magnitude lower than the commonly used Holzworth (1972) method and the ceilometer estimated mixing heights. Additionally, on average, the ceilometer exhibited a daily maximum mixing height value that occurred 1-3 hours later than the AERMET estimated maximum. This difference is likely due to the nighttime atmospheric mixing height assumptions and calculations used by AERMET. The AERMET algorithm cuts off mixing height growth at sunset while the ceilometer data show ongoing evening convection typical of the southeastern United States. These results suggest that the AERMET parametrization scheme assumptions may not be representative of a forested landscape and evening convection which could account for more mixing overnight. The results obtained in this study are significant for air dispersion modeling applications for regulatory purposes and worker safety. Mixing height can impact model estimated pollutant concentrations. A greater mixing height will provide more volume for pollutant dispersion. This report documents efforts to quantify the dependence of mixing height inputs toward a conservative estimated pollutant concentration.
- Research Organization:
- Savannah River National Laboratory (SRNL), Aiken, SC (United States)
- Sponsoring Organization:
- USDOE Office of Environmental Management (EM); USDOE Office of Science (SC), Office of Workforce Development for Teachers & Scientists (WDTS)
- DOE Contract Number:
- 89303321CEM000080
- OSTI ID:
- 2570402
- Report Number(s):
- SRNL--STI-2025-00294
- Country of Publication:
- United States
- Language:
- English
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