Monthly top‐down NO_x emissions for China (2005–2012): A hybrid inversion method and trend analysis

Abstract

We develop an approach combining mass balance and four‐dimensional variational (4D‐Var) methods to facilitate inversion of decadal‐scale total nitrogen oxides (NOx = NO + NO2) emissions. In 7 year pseudo‐observation tests, hybrid posterior emissions have smaller normalized mean square error (NMSE) than that of mass balance when compared to true emissions in most cases and perform slightly better in detecting NOx emission magnitudes and trends. Using this hybrid method, OMI NO2 satellite observations and the GEOS‐Chem chemical transport model, we find more than 30% increases of emissions over most of East China at the 0.5° × 0.667° grid cell level, leading to a 16% growth of emissions over all of China from 2005 to 2012, whereas emissions in several urban centers have decreased by 10–26% in the same period. From 2010 to 2012, a decline is found in the North China Plain, Hubei Province, and Pearl River Delta area, coinciding with China's enforcement of its twelfth “Five Year Plan.” Changes in individual grid cell may be different from changes over the entire city or province, as exemplified by opposite trends in Beijing versus the Mentougou district of Beijing from 2005 to 2012. Also, NO2 columns do not necessarily have the same trend as NOx emissions due to their nonlinear response to emissions and the influence of meteorology, the latter alone which can cause up to 30% interannual changes in NO2 columns. Compared to recent bottom‐up inventories, hybrid posterior emissions have the same seasonality, smaller emissions, and emission growth rate at the national scale.

The Ozone Monitoring Instrument: overview of 14 years in space

“…These describe trends in aerosol presence for the regions over the entire time range covered by the time series. port models (Qu et al, 2017). Streets et al (2013) reviewed the current capability to estimate emissions from space, and in this section we highlight studies of emissions using OMI data that have been published subsequently.…”

“…For total column O 3 the average differences were < 12 DU (or 3.9 %) with OMI greater than Pandora. Reed et al (2015) also compared Pandora with OMI during the Baltimore/Washington campaign and found that OMI pixel size, clouds, and aerosols affected OMI retrievals causing differences between Pandora and OMI of up to 65 % for total column NO 2 and 23 % for total column O 3 .…”

Agricultural ammonia emissions in China: reconciling bottom-up and top-down estimates

“…The model adjoint is first described by Henze et al (2007) for aerosols and Kopacz et al (2009) for carbon monoxide. It has been highly validated and applied in studies to analyze aerosol sensitivities and constrain aerosol sources in the United States Zhu et al, 2013;Mao et al, 2015) and China (Kharol et al, 2013;Zhang et al, 2015Zhang et al, , 2016Qu et al, 2017).…”

High-resolution inversion of OMI formaldehyde columns to quantify isoprene emission on ecosystem-relevant scales: application to the Southeast US

“…Here we 10 calculate the AMF by applying the local OMI scattering weights from the operational retrieval to the GEOS-Chem HCHO vertical profile (Qu et al, 2017 Single-scene measurement error includes (1) the spectral fitting error reported as part of the operational product, and (2) the error in the AMF calculation, which increases from 15% under clear sky conditions to 20% at a cloud fraction of 0.3 (Millet et al, 2006). We increase the spectral fitting error by a factor of 1.59, the same factor used to correct the mean bias in OMI VCDs.…”