Atmospheric Simulations of Total Column CO2 Mole Fractions from Global to Mesoscale within the Carbon Monitoring System Flux Inversion Framework

Martha P. Butler,Junjie Liu,Sha Feng,Thomas Lauvaux,Kenneth J. Davis,Kevin W. Bowman

doi:10.3390/atmos11080787

Abstract

Quantifying the uncertainty of inversion-derived CO2 surface fluxes and attributing the uncertainty to errors in either flux or atmospheric transport simulations continue to be challenges in the characterization of surface sources and sinks of carbon dioxide (CO2). Despite recent studies inferring fluxes while using higher-resolution modeling systems, the utility of regional-scale models remains unclear when compared to existing coarse-resolution global systems. Here, we present an off-line coupling of the mesoscale Weather Research and Forecasting (WRF) model to optimized biogenic CO2 fluxes and mole fractions from the global Carbon Monitoring System inversion system (CMS-Flux). The coupling framework consists of methods to constrain the mass of CO2 introduced into WRF, effectively nesting our regional domain covering most of North America (except the northern half of Canada) within the CMS global model. We test the coupling by simulating Greenhouse gases Observing SATellite (GOSAT) column-averaged dry-air mole fractions (XCO2) over North America for 2010. We find mean model-model differences in summer of ∼0.12 ppm, significantly lower than the original coupling scheme (from 0.5 to 1.5 ppm, depending on the boundary). While 85% of the XCO2 values are due to long-range transport from outside our North American domain, most of the model-model differences appear to be due to transport differences in the fraction of the troposphere below 850 hPa. Satellite data from GOSAT and tower and aircraft data are used to show that vertical transport above the Planetary Boundary Layer is responsible for significant model-model differences in the horizontal distribution of column XCO2 across North America.

Highlights

One of the persistent challenges in the study of the global carbon cycle is the quantification of the uncertainty in inferred biogenic carbon sources and sinks [1]
This first result demonstrates the decrease in the bias introduced in Weather Research and Forecasting (WRF) by using a mass-conserved coupling scheme, whereas the original coupling artificially increases the amount of CO2 molecules in the atmosphere
In order to understand the differences in total columns, we present an analysis of vertical profiles of CO2 mole fractions in Figure 10 focusing on two NOAA aircraft profile sites, one near West Branch, Iowa (WBI) in the central part of the US Corn Belt, and a second on the East Coast of the US near

Summary

Introduction

One of the persistent challenges in the study of the global carbon cycle is the quantification of the uncertainty in inferred biogenic carbon sources and sinks [1]. Contemporary solution methods include atmospheric inversions while using general circulation models and in situ or satellite observations of carbon dioxide (CO2 ) to correct vegetation model or flux-derived estimates of these biogenic surface. In spite of increasing sophistication in the optimization methods and observation systems, annual inverse fluxes vary widely at continental scales, e.g., from 0 to. Atmosphere 2020, 11, 787 from the Orbiting Carbon Observatory (OCO)-2 NASA mission estimated the range of uncertainties between −0.5 to −1.6 PgC over North America. Contributions to this disagreement include poor representation of the heterogeneous land surface in relatively coarse general circulation models [7], as well as aggregation and atmospheric transport errors [8].

Objectives

Results

Discussion

Conclusion