Inverse modeling of European CH&amp;lt;sub&amp;gt;4&amp;lt;/sub&amp;gt; emissions: sensitivity to the observational network

M G Villani,P Bergamaschi,F Dentener,J F Meirink,M Krol

doi:10.5194/acp-10-1249-2010

Abstract

Abstract. Inverse modeling is widely employed to provide "top-down" emission estimates using atmospheric measurements. Here, we analyze the dependence of derived CH4 emissions on the sampling frequency and density of the observational surface network, using the TM5-4DVAR inverse modeling system and synthetic observations. This sensitivity study focuses on Europe. The synthetic observations are created by TM5 forward model simulations. The inversions of these synthetic observations are performed using virtually no knowledge on the a priori spatial and temporal distribution of emissions, i.e. the emissions are derived mainly from the atmospheric signal detected by the measurement network. Using the European network of stations for which continuous or weekly flask measurements are available for 2001, the synthetic experiments can retrieve the "true" annual total emissions for single countries such as France within 20%, and for all North West European countries together within ~5%. However, larger deviations are obtained for South and East European countries due to the scarcity of stations in the measurement network. Upgrading flask sites to stations with continuous measurements leads to an improvement for central Europe in emission estimates. For realistic emission estimates over the whole European domain, however, a major extension of the number of stations in the existing network is required. We demonstrate the potential of an extended network of a total of ~60 European stations to provide realistic emission estimates over the whole European domain.

Highlights

Inverse modeling of atmospheric CH4 provides “top-down” emission estimates, and represents an important tool to analyze the global CH4 budget (Bergamaschi et al, 2009; Chen and Prinn, 2006; Bousquet et al, 2005; Mikaloff Fletcher et al, 2004a, b; Houweling et al, 1999; Hein et al, 1997)
We demonstrate the potential of an extended network of a total of ∼60 European stations to provide realistic emission estimates over the whole European domain
We first analyze the potential of single stations to retrieve CH4 emissions over Europe

Summary

Introduction

Inverse modeling of atmospheric CH4 provides “top-down” emission estimates, and represents an important tool to analyze the global CH4 budget (Bergamaschi et al, 2009; Chen and Prinn, 2006; Bousquet et al, 2005; Mikaloff Fletcher et al, 2004a, b; Houweling et al, 1999; Hein et al, 1997). Inverse modeling efforts have been extended to the regional scale (e.g. on the spatial scales of single countries), using high-resolution models and better coverage of measurements (Bergamaschi et al, 2005; Manning et al, 2005). Such regional top-down estimates can be potentially used for verification of international agreements on emission reductions, such as the Kyoto protocol, which requires constant monitoring in a dense network (Bergamaschi, 2007a; IPCC, 2000). Large observational data sets can be used, such as high frequency in situ measurements, providing constraints on monthly emissions from concentration variations at synoptic time scales

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