(79-130415-A) Updated Estimates of California’s Urban and Rural Methane Emissions
M.L. Fischer1, S. Jeong1, E. Novakovskaia2, A.E. Andrews3, L. Bianco3, H. Graven4, Y. Hsu5, S. Newman6, P. Vaca5, A.V. Pelt7, R. Weiss4 and R. Keeling4
1Lawrence Berkeley National Laboratory, Berkeley, CA 94720; 510-486-5539, E-mail: email@example.com
2Earth Networks, Inc., Germantown, MD 20876
3NOAA Earth System Research Laboratory, Boulder, CO 80305
4University of California at San Diego, Scripps Institution of Oceanography, La Jolla, CA 92093
5California Air Resources Board, Sacramento, CA 95812
6California Institute of Technology, Pasadena, CA 91125
7Picarro Inc, Santa Clara, CA 94054
We present updated atmospheric inversion estimates of California’s total CH4 emissions for 3 months (June-August) in summer 2012. Measurements include data from 9 sites covering urban and rural areas of California’s South Coast Air Basin, Central Valley, San Francisco Bay Area, and North Coast. We use Bayesian inversions to estimate the CH4 emissions from discrete regions of California by combining the local CH4 measurements, background CH4, 0.1 degree prior model emission maps (one specific to California and one global), and predicted CH4 signals from the Weather Research and Forecasting/Stochastic Time-Inverted Langrangian Transport atmospheric transport model. We quantify site-specific model-measurement uncertainties due to: 1) transport using meteorological data from a network of atmospheric profilers and in situ sensors, 2) background using oceanic and aircraft observations, and 3) prior emissions using the spread results obtained with the two different maps. Bayesian inverse modeling using the network of measurements constrains a majority (>90%) of California’s emissions. Here, we update the emission estimates and uncertainties and compare our results with previous studies covering smaller areas and time periods.
Figure 1. CH4 emissions by region for California showing prior (annual average), and posterior estimates (June, July, August) from the inversion of network data.