Study of the footprints of short-term variation in XCO<sub>2</sub> observed by TCCON sites using NIES and FLEXPART atmospheric transport models

Abstract

Abstract. The Total Carbon Column Observing Network (TCCON) is a network of ground-based Fourier transform spectrometers (FTSs) that record near-infrared (NIR) spectra of the sun. From these spectra, accurate and precise observations of CO 2 column-averaged dry-air mole fractions (denoted XCO 2 ) are retrieved. TCCON FTS observations have previously been used to validate satellite estimations of XCO 2 ; however, our knowledge of the short-term spatial and temporal variations in XCO 2 surrounding the TCCON sites is limited.In this work, we use the National Institute for Environmental Studies (NIES) Eulerian three-dimensional transport model and the FLEXPART (FLEXible PARTicle dispersion model) Lagrangian particle dispersion model (LPDM) to determine the footprints of short-term variations in XCO 2 observed by operational, past, future and possible TCCON sites. We propose a footprint-based method for the collocation of satellite and TCCON XCO 2 observations and estimate the performance of the method using the NIES model and five GOSAT (Greenhouse Gases Observing Satellite) XCO 2 product data sets. Comparison of the proposed apPublished by Copernicus Publications on behalf of the European Geosciences Union. proach with a standard geographic method shows a higher number of collocation points and an average bias reduction up to 0.15 ppm for a subset of 16 stations for the period from January 2010 to January 2014. Case studies of the Darwin and Reunion Island sites reveal that when the footprint area is rather curved, non-uniform and significantly different from a geographical rectangular area, the differences between these approaches are more noticeable. This emphasises that the collocation is sensitive to local meteorological conditions and flux distributions.

Total Carbon Column Observing Network Philippines: Toward Quantifying Atmospheric Carbon in Southeast Asia

“…To estimate the measurement sensitivity to surface fluxes (here called "footprints") at the TCCON site, the study employed the same method as described in Belikov et al (2017). Forward simulations for the footprints were derived from the NIES Eulerian three-dimensional transport model (TM).…”

“…FLEXPART considers atmospheric tracers as a discrete phase and tracks the pathway of each individual particle (Stohl et al, 2009). These footprints are also shown in Belikov et al (2017).…”

A segmentation algorithm for characterizing rise and fall segments in seasonal cycles: an application to XCO<sub>2</sub> to estimate benchmarks and assess model bias

“…Much focus has been put on accurately characterizing component fluxes from land use and land cover change simulated by DGVMs (Pongratz et al, 2014;Calle et al, 2016), but we also show that LUC influences the atmospheric seasonal cycle period and phase at a level that is comparable to the reference rates of interannual variation in those metrics ( Table 3). This underscores the complex problem of trying to simultaneously resolve the contribution of LUC fluxes to the long-term trend in atmospheric CO 2 (Le Quéré et al, 2018) and also to represent realistic LUC effects on seasonal-scale biosphere activity (Betts et al, 2013;Bagley et al, 2014). For instance, when land is converted from forest to pasture, the dominant land cover will affect the duration and timing of the surface fluxes (Fleischer et al, 2016) and this seems obvious.…”

Modelling CO<sub>2</sub> weather – why horizontal resolution matters

“…It is likely that the larger footprint of XCO 2 (Belikov et al, 2017) at most TCCON stations -associated with its sensitivity to large-scale flux patterns -(Keppel-Aleks et al, 2011, 2012) is causing most TCCON sites to be less sensitive to horizontal resolution. However, there is a large variation in RMSE between sites (see σ RMSE in Fig.…”