TY - JOUR
T1 - Seasonal variation of CH4 emissions from central California
JF - Journal of Geophysical Research - Atmospheres
Y1 - 2012/
A1 - Seongeun Jeong
A1 - Chuanfeng Zhao
A1 - Arlyn E. Andrews
A1 - Laura Bianco
A1 - James M. Wilczak
A1 - Marc L. Fischer
KW - atmospheric transport
KW - emission inventory
KW - greenhouse gas
KW - inverse model
KW - methane
AB - We estimate seasonal variations in methane (CH4) emissions from central California from December 2007 through November 2008 by comparing CH4 mixing ratios measured at a tall tower with transport model predictions based on a global 1° a priori CH4emissions map (EDGAR32) and a 10 km seasonally varying California-specific map, calibrated to statewide by CH4emission totals. Atmospheric particle trajectories and surface footprints are computed using the Weather Research and Forecasting and Stochastic Time-Inverted Lagrangian Transport models. Uncertainties due to wind velocity and boundary layer mixing depth are evaluated using measurements from radar wind profilers. CH4signals calculated using the EDGAR32 emission model are larger than those based on the California-specific model and in better agreement with measurements. However, Bayesian inverse analyses using the California-specific and EDGAR32 maps yield comparable annually averaged posterior CH4emissions totaling 1.55 ± 0.24 times and 1.84 ± 0.27 times larger than the California-specific prior emissions, respectively, for a region of central California within approximately 150 km of the tower. If these results are applicable across California, state total CH4 emissions would account for approximately 9% of state total greenhouse gas emissions. Spatial resolution of emissions within the region near the tower reveal seasonality expected from several biogenic sources, but correlations in the posterior errors on emissions from both prior models indicate that the tower footprints do not resolve spatial structure of emissions. This suggests that including additional towers in a measurement network will improve the regional specificity of the posterior estimates.
VL - 117
IS - D11
DO - 10.1029/2011JD016896
ER -
TY - JOUR
T1 - Seasonal variations in N_{2}O emissions from central California
JF - Geophysical Research Letters
Y1 - 2012/
A1 - Seongeun Jeong
A1 - Chuanfeng Zhao
A1 - Arlyn E. Andrews
A1 - Edward J. Dlugokencky
A1 - Colm Sweeney
A1 - Laura Bianco
A1 - James M. Wilczak
A1 - Marc L. Fischer
KW - atmospheric transport
KW - inverse modeling
KW - nitrous oxide
AB - We estimate nitrous oxide (N2O) emissions from Central California for the period of December 2007 through November 2009 by comparing N2O mixing ratios measured at a tall tower (Walnut Grove, WGC) with transport model predictions based on two global a priori N2O emission models (EDGAR32 and EDGAR42). Atmospheric particle trajectories and surface footprints are computed using the Weather Research and Forecasting (WRF) and Stochastic Time-Inverted Lagrangian Transport (STILT) models. Regression analyses show that the slopes of predicted on measured N2O from both emission models are low, suggesting that actual N2O emissions are significantly higher than the EDGAR inventories for all seasons. Bayesian inverse analyses of regional N2O emissions show that posterior annual N2O emissions are larger than both EDGAR inventories by factors of 2.0 ± 0.4 (EDGAR32) and 2.1 ± 0.4 (EDGAR42) with seasonal variation ranging from 1.6 ± 0.3 to 2.5 ± 0.4 for an influence region of Central California within approximately 150 km of the tower. These results suggest that if the spatial distribution of N2O emissions in California follows the EDGAR emission models, then actual emissions are 2.7 ± 0.5 times greater than the current California emission inventory, and total N2O emissions account for 8.1 ± 1.4% of total greenhouse gas emissions from California.
VL - 39
IS - 16
DO - 10.1029/2012GL052307
ER -
TY - JOUR
T1 - Atmospheric inverse estimates of methane emissions from Central California
JF - Journal of Geophysical Research - Atmospheres
Y1 - 2009/
A1 - Chuanfeng Zhao
A1 - Arlyn E. Andrews
A1 - Laura Bianco
A1 - Janusz Eluszkiewicz
A1 - Adam Hirsch
A1 - Clinton MacDonald
A1 - Thomas Nehrkorn
A1 - Marc L. Fischer
KW - atmospheric transport
KW - inverse modeling
KW - methane
AB - [1] Methane mixing ratios measured at a tall tower are compared to model predictions to estimate surface emissions of CH4 in Central California for October–December 2007 using an inverse technique. Predicted CH4 mixing ratios are calculated based on spatially resolved a priori CH4 emissions and simulated atmospheric trajectories. The atmospheric trajectories, along with surface footprints, are computed using the Weather Research and Forecast (WRF) coupled to the Stochastic Time-Inverted Lagrangian Transport (STILT) model. An uncertainty analysis is performed to provide quantitative uncertainties in estimated CH4 emissions. Three inverse model estimates of CH4 emissions are reported. First, linear regressions of modeled and measured CH4 mixing ratios obtain slopes of 0.73 ± 0.11 and 1.09 ± 0.14 using California-specific and Edgar 3.2 emission maps, respectively, suggesting that actual CH4 emissions were about 37 ± 21% higher than California-specific inventory estimates. Second, a Bayesian "source" analysis suggests that livestock emissions are 63 ± 22% higher than the a priori estimates. Third, a Bayesian "region" analysis is carried out for CH4 emissions from 13 subregions, which shows that inventory CH4 emissions from the Central Valley are underestimated and uncertainties in CH4 emissions are reduced for subregions near the tower site, yielding best estimates of flux from those regions consistent with "source" analysis results. The uncertainty reductions for regions near the tower indicate that a regional network of measurements will be necessary to provide accurate estimates of surface CH4 emissions for multiple regions.
VL - 114
IS - D16
ER -