Constraining historical black carbon emission inventory of United States for 1960 s2000 s

To improve the accuracy of black carbon emission inventory of US for 1960s to 2000s, we studied the relationship between emissions and ambient air concentrations of BC using the Community Atmosphere Model and formulated it into matrices that allow reconstruction of BC ambient concentration with emission inventory. Errors in model meteorology are corrected in the transport matrices by adjustment with measurements from NASA. We also applied Heating Degree Days data to estimate seasonal variation in emissions, as observed from the concentrations. Comparison between the reconstructed and measured BC shows that the magnitude of observations was decreasing throughout this period of time, while the reconstructed concentrations peaked in the 1980s. Also, scaling heating emissions by HDD can explain most of the trend in seasonal variation observed in the measurements. Acknowledging the inherent uncertainty in model-measurement comparison, we rely more on the trends comparison. Apparent adjustment factors are calculated for baseline and seasonal emissions for each decade. To reproduce the decreasing trend, higher emission factors are needed for 1960s to 1970s. More information is required to further improve the emission inventory on fuel consumption and technology level.