Imposing strong constraints on tropical terrestrial CO₂ fluxes using passenger aircraft based measurements

Abstract

[1] Because very few measurements of atmospheric carbon dioxide (CO 2 ) are available in the tropics, estimates of surface CO 2 fluxes in tropical regions are beset with considerable uncertainties. To improve estimates of tropical terrestrial fluxes, atmospheric CO 2 inversion was performed using passenger aircraft based measurements of the Comprehensive Observation Network for Trace gases by Airliner (CONTRAIL) project in addition to the surface measurement data set of GLOBALVIEW-CO 2 . Regional monthly fluxes at the earth's surface were estimated using the Bayesian synthesis approach focusing on the period 2006-2008 using the Nonhydrostatic Icosahedral Atmospheric Model-based Transport Model (NICAM-TM). By adding the aircraft to the surface data, the posterior flux errors were greatly reduced; specifically, error reductions of up to 64% were found for tropical Asia regions. This strong impact is closely related to efficient vertical transport in the tropics. The optimized surface fluxes using the CONTRAIL data were evaluated by comparing the simulated atmospheric CO 2 distributions with independent aircraft measurements of the Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container (CARIBIC) project. The inversion with the CONTRAIL data yields the global carbon sequestration rates of 2.22 AE 0.28 Pg C yr À1 for the terrestrial biosphere and 2.24 AE 0.27 Pg C yr À1 for the oceans (the both are adjusted by riverine input of CO 2 ). For the first time the CONTRAIL CO 2 measurements were used in an inversion system to identify the areas of greatest impact in terms of reducing flux uncertainties.

A 4D-Var inversion system based on the icosahedral grid model (NICAM-TM 4D-Var v1.0) – Part 2: Optimization scheme and identical twin experiment of atmospheric CO<sub>2</sub> inversion

“…This property is absolutely necessary for transport simulations of long-lived tracers such as GHGs. Because of this, NICAM-TM has been developed and used for transport and inversion studies of CO 2 Patra et al, 2008;Niwa et al, 2011bNiwa et al, , 2012Peylin et al, 2013). Its fundamental transport performances have been evaluated satisfactorily using observations of radon ( 222 Rn) and sulfur hexafluoride (SF 6 ) (Niwa et al, 2011a(Niwa et al, , 2012.…”

“…Therefore, fluxes other than the fossil fuel emissions are optimized in the identical twin experiment. For the true flux dataset, we use the net ecosystem production (NEP) data of the Carnegie-Ames-Stanford Approach (CASA) model (Randerson et al, 1997) modified by the inversion of Niwa et al (2012), and the climatological pCO 2 -based sea-air exchange data of Takahashi et al (2009). The reason for the inversion modification of the CASA flux field is that the original CASA NEP is annually balanced (that is, annually integrated flux is zero everywhere).…”

Estimation of Asian and Global Carbon Fluxes Using Maximum Likelihood Ensemble Filter (MLEF)

“…Those studies highlighted the importance of the collecting more CO 2 observations using new methods in order to achieve good estimates for the CO 2 fluxes. Niwa et al (2012) has mentioned that the lack of measurements at the surface can be partially compensated by satellite observations and increasingly by aircraft measurements in the free troposphere.…”

“…The spatial and temporal distribution of CO 2 fluxes provides more information about the global carbon cycle, which has been analyzed using inverse methods to estimate regional sources and sinks. The literature is rich on inverse modelling and several applications to CO 2 fluxes are Tans et al, 1990;Gurney et al, 2002;Rodenbeck et al, 2003;Michalak et al, 2004;Bruhwiler et al 2005;Peters et al 2005;Zupanski et al 2007a;Lokupitiya et al 2008;"Carbon Tracker", 2011;Niwa et al 2012;Jiang et al 2014;Zhang et al 2014;Thompson et al 2016.…”

Evaluation of a new JMA aircraft flask sampling system and laboratory trace gas analysis system

“…Current attempts to infer trace gas emissions in East Asia by various top-down inverse methods are limited by the sparseness of the available observation data. In particular, aircraft measurements above the planetary boundary layer are useful in constraining and reducing larger uncertainties of regional flux estimates by inversion calculations (e.g., Stephens et al, 2007;Niwa et al, 2012). Thus, maintaining and expanding multispecies observations of atmospheric trace gases over the western North Pacific is necessary to evaluate rapid changes in anthropogenic emissions and their influences from East Asia.…”