1. Inverse Modeling of NH3 EmissionsUsingTime-Averaged Concentrations Kira Shonkwiler Department of Atmospheric Science, Colorado State University

2. Inverse Modeling What ifwind You cant directly Cattle PensNorth measure emissions? West Base The instruments are too expensive? 700 m South You only know N concentration? Know average concentration, windcharacteristics, and site layout Can estimate how much was emitted for that location to report that concentration! 3. FIDES Flux Interpretation by Dispersion Exchangeover Short-range (FIDES) Inverse model (inputs: u* and L) Solves the advection-dispersion equation Uses concentration ( ) from a location (x, z) to estimatesource strength of a different location (xs, zs) Cbgd is the constant background concentration S is the source strength D is a dispersion functionLoubet et al., 2001; 2010 4. FIDES Applied successfully in Europe (Loubet et al., 2001; 2009; 2010) NH3 concentrations measured with high-speedinstrumentation Expensive Work at CSU is first attempt at modeling NH3emissions from time-averaged data (i.e., theconditional passive samplers) 5. Model Output Emissions Average emissions for each deployment cycle (Oct 2012 Feb 2013) Decrease in volatilization from surface during winter 6. Model Output EmissionsHistogram (frequency distribution) of output emissions from FIDES Skewed distribution, 92% of values fall between 20 100 g m-2 s-1 7. Model Output EmissionsEmissions summary Average Emissions: 4.7 g m-2 d-1; 41 g head-1 d-1 Percent of Fed-Nitrogen emitted as NH3 averaged 53% 8. Conclusions Emissions decreased throughout the winter as volatilization decreased Predicted emissions have a skewed distribution Average output from the model was 20 100 g m-2 s-1 Emissions averaged 41 g head-1 d-1 and 4.7 g m-2 d-1 53% of Fed N emitted to air as NH3 9. References1. FdfsThank You!