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Ammonia Emissions in China: Bottom-Up vs. Top-Down Estimates

This study compares bottom-up and top-down estimates of ammonia emissions in China, highlighting strong seasonality and the need for improved quantification of fertilizer use. The results show large uncertainties in bottom-up estimates and suggest the importance of considering agricultural practices for better emission seasonality.

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Ammonia Emissions in China: Bottom-Up vs. Top-Down Estimates

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  1. Bottom-up and top-down estimates of ammonia emissions over China 1. Peking U. 2. Chinese Academy of Sciences 3. U. of Colorado, Boulder Lin Zhang1 (zhanglg@pku.edu.cn), Yuanhong Zhao1, Youfan Chen1, Yuepeng Pan2, Yuesi Wang2, Daven Henze3 • Key messages: • Top-down NH3 emission estimates over China suggest a strong seasonality with emission in summer much higher than winter. • We provide a new bottom-up estimate of Chinese NH3 emissions from fertilizer use which better quantifies the fertilizer application procedure to improve the emission seasonality. The GEIA 2015 Conference 18-20 November 2015

  2. Large uncertainties in bottom-up Asian NH3 emissions NH3 emissions from REAS-2 (Kurokawa ACP 2013) Differences with Streets et al. (JGR 2003) 50%-100% difference

  3. Bayesian inversion of NH3 emissions over the North China using measurements of concentrations and wet deposition fluxes Observations (2007-2010) GEOS-Chem (REAS-2 no seasonality) GEOS-Chem (Optimized) NH4+ wet 10 sites from CAS NH3 concentration

  4. Adjoint inversion of Asian NH3 emissions for July using the TES satellite measurements Scaling factors r = 0.56 bias=-43% r = 0.63 bias=-0.1% 1.3 r = 0.29 bias=-65% r = 0.49 bias=-9% 2.1 r = 0.59 bias=-38% r = 0.62 bias=-14% 1.4 The inversion results show large sensitivity to the prior emissions used and the model horizontal resolution. Inverse results for July would give a range of 1.62-2.61 Tg.

  5. Revisiting bottom-up NH3 emission estimates from fertilizer use Needs to better quantify how fertilizers are applied in China over different agricultural crops (more practical timing and magnitude of fertilizer use) Total fertilizer application rates over China in 2008 for 18 crop types

  6. Improved seasonality of Chinese NH3 emissions from fertilizer use 2008 fertilizer use over China: spatial and seasonal variations 2008 NH3 emissions from fertilizer use over China Annual total 4.95 Tg NH3, peaking in late spring and early summer [Zhang et al. in prepare]

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