Estimating CH4 Emissions in California Using Measurements from a Tower Network
Abstract
We estimate regionally resolved methane (CH4) emissions for California using a Bayesian inverse model driven by CH4 mixing ratios measured at a network of five towers across the Central Valley during 2010 - 2011. The method estimates emissions by comparing measurements with transport model predictions of CH4 signals obtained from two 0.1 degree prior emission maps: 1) seasonally varying "California-specific" emission maps, calibrated to State emission totals, and 2) the EDGAR4.2 static global emission map. Atmospheric transport is calculated from particle trajectories and surface footprints using the Weather Research and Forecasting (WRF) and Stochastic Time-Inverted Lagrangian Transport (STILT) models. Results for the 5-tower CARB-CEC-LBNL-NOAA network show that significant reductions in posterior emissions uncertainty are obtained for regions comprising ~ 90% of California's known CH4 emissions, with annually averaged emissions totaling 1.6+/-0.1 and 2.5+/-0.3 times California's inventory for the California-specific and EDGAR4.2 emissions maps, respectively. Assuming these results apply across California, total CH4 emissions account for approximately 8% - 14% of current state total greenhouse gas emissions. The magnitude and uncertainty of emissions from specific regions and source sectors (e.g., crop agriculture, waste management, livestock, and energy activities) are estimated by comparing region and source sector results obtained with the CA-specific and EDGAR4.2 emission maps.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFM.A24A..06J
- Keywords:
-
- 0365 ATMOSPHERIC COMPOSITION AND STRUCTURE / Troposphere: composition and chemistry;
- 0368 ATMOSPHERIC COMPOSITION AND STRUCTURE / Troposphere: constituent transport and chemistry;
- 0490 BIOGEOSCIENCES / Trace gases;
- 3355 ATMOSPHERIC PROCESSES / Regional modeling