A Journey through Terrain and Weather: Multiscale Influences on Potential Concentrations at Monitoring Sites

For many emissions monitoring applications, networks of measurement sites are used to detect and potentially attribute the source of the emissions. For example, atmospheric measurements of radionuclides (RN) can contribute to nuclear test monitoring. However, quantifying the effects of physical processes that affect the transport and dispersion of radionuclides between the source and measurement locations is an ongoing area of research. In addition, other RN sources, such as medical isotope production facilities, can potentially contribute to RN concentrations at measurement sites, complicating the interpretation of the measurements.

In an effort to better understand the behavior of releases to the atmosphere, we performed numerical simulations with the Weather Research and Forecasting Model coupled to Chemistry (WRF-Chem). This study investigates the hypothesis that complex topography near emissions sources can influence plume concentrations at measurement sites at local to continental distances from the source. Two hypothetical, non-buoyant tracer point sources are modeled during the two-week simulations that are initiated and nudged by synoptic weather from January 2011, over the continental U.S. The sources include a large, discrete source, near Salt Lake City, UT, representing a short duration event of interest on the fourth day of the simulations and a relatively low flux rate source that varied with time for the duration of the runs, at Reno, NV, representing a nuisance source that also contributes RN to the atmosphere. The impact of grid resolution on concentrations at simulated monitoring locations from kilometers to thousands of kilometers away will be presented. The importance of source location and the influence of the nuisance source on concentrations at measurement sites will also be analyzed. The discussion will include the collective roles of topography and synoptic weather on the plume transport.