Atmospheric constraints on 2004 emissions of methane and nitrous oxide in North America from atmospheric measurements and a receptor-oriented modeling framework

Abstract

Methane and nitrous oxide are potent greenhouse gases whose atmospheric abundances have increased significantly in the past 200 years, together accounting for approximately half of the radiative forcing associated with increasing concentrations of carbon dioxide. In order to understand the factors causing increase of these gases globally, we need to determine their emission rates at regional to continental scales. We directly link atmospheric observations with surface emissions using a Lagrangian Particle Dispersion Model, and then determine emission rates by optimizing prior emissions estimates. We use measurements from NOAA's tall tower and aircraft program in 2004, The Stochastic Time-Inverted Lagrangian Transport model (STILT) driven by meteorological fields from a customized version of the Weather Research and Forecasting (WRF) model, and EDGAR32FT2000 and Global Emissions Inventory Activity (GEIA) as prior emission estimates. In the US and Canada, methane emission rates are found to be consistent with observations, while nitrous oxide emissions are significantly low, by a factor 2.5-3 in the peak emissions time period found to be February through May.

Regional sources of nitrous oxide over the United States: Seasonal variation and spatial distribution

“…The budget numbers presented here compare well to those estimated in previous top‐down studies over North America, notably those by Kort et al [2008, 2010]. These studies estimated a US and Canada N 2 O budget of 0.23 TgN/month for spring and summer months in 2003 and 2004.…”

Nitrous Oxide Emissions Estimated With the CarbonTracker‐Lagrange North American Regional Inversion Framework

“…Several previous regional inversions over North America have suggested that the EDGAR inventory might underestimate U.S. Midwestern N 2 O emissions by a factor of~3 (Kort et al, 2008(Kort et al, , 2010Miller et al, 2012). This finding generally is not supported by our results, which extend over a longer time scale and are constrained by a more comprehensive network of measurements than previous results.…”

Anthropogenic emissions of methane in the United States

“…Most regional studies adopted one of three approaches: use a simple box model to estimate an overall CH 4 budget (14), estimate a budget using the relative ratios of different gases (15,(37)(38)(39), or estimate scaling factors for inventories by region or source type (13,(34)(35)(36). The first two methods do not usually give explicit information about geographic distribution.…”