Evaluating Atmospheric Ammonia Dynamics: Open-path Measurements and Model Comparisons
Speaker: David Miller, Graduate Student
Series: EEWR Brown Bag Seminars
Location: Engineering Quad E225
Date/Time: Friday, March 2, 2012, 12:00 p.m. - 1:00 p.m.
Atmospheric ammonia, the third most abundant nitrogen species and dominant atmospheric base, is an important precursor to fine particulate matter. Gas phase ammonia measurements are crucial for understanding aerosol processes, with implications for air quality, climate change and reactive nitrogen cycling. Anthropogenic ammonia emission inventories exhibit larguncertainties in part due to a lack of measurements. A novel, compact, openpatquantum cascade laser-based atmospheric ammonia sensor has beedeveloped for high sensitivity, fast, ground-based measurements. The performance of this open-path ammonia sensor, including fast response to local emission sources and measurements in a range of field environments, will be presented. Field measurements during the CALNEX 2010 field campaign in Bakersfield, California are evaluated to analyze ammonia diurnal cycle contributions from emission sources, transport and boundary layer mixing processes. These measurements, along with urban measurements in Baltimore, Maryland, are compared with GFDL AM3 model simulation results. Significant discrepancies exist between observed and modeled ammonia concentrations, with emission inventories contributing to model prediction uncertainties. Future work will include extensive urban measurements, model sensitivity analyses and satellite observation comparisons.