{'fraction_non_alphanumeric': 0.04459016393442623, 'fraction_numerical': 0.04131147540983607, 'mean_word_length': 5.178137651821863, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
A multi-platform inversion estimation of statewide and regional methane emissions in California during 2014-2016.

California methane (CH4) emissions are quantified for three years from two tower networks and one aircraft campaign. We used backward trajectory simulations and a mesoscale Bayesian inverse model, initialized by three inventories, to achieve the emission quantification. Results show total statewide CH4 emissions of 2.05±0.26 (at 95% confidence) Tg/yr, which is 1.14 to 1.47 times greater than the anthropogenic emission estimates by California Air Resource Board (CARB). Some of differences could be biogenic emissions, super-emitter point sources, and other episodic emissions which may not be completely included in the CARB inventory. San Joaquin Valley (SJV) has the largest CH4 emissions (0.94±0.18 Tg/yr), followed by the South Coast Air Basin, the Sacramento Valley, and the San Francisco Bay Area, 0.39±0.18, 0.21±0.04, and 0.16±0.05 Tg/yr, respectively. The dairy and oil/gas production sources in the SJV contribute 0.44±0.36 and 0.22±0.23 Tg CH4/yr, respectively. This study has important policy implications for regulatory programs, as it provides a thorough multi-year evaluation of the emissions inventory using independent atmospheric measurements, and investigates the utility of a complementary multi-platform approach in understanding the spatial and temporal patterns of CH4 emissions in the state, and identifies opportunities for the expansion and applications of the monitoring network.