Observing the continental-scale carbon balance: assessment of sampling complementarity and redundancy in a terrestrial assimilation system by means of quantitative network design

T Kaminski,E Koffi,M Scholze,M Voßbeck,P J Rayner

doi:10.5194/acp-12-7867-2012

Abstract

Abstract. This paper investigates the relationship between the heterogeneity of the terrestrial carbon cycle and the optimal design of observing networks to constrain it. We combine the methods of quantitative network design and carbon-cycle data assimilation to a hierarchy of increasingly heterogeneous descriptions of the European terrestrial biosphere as indicated by increasing diversity of plant functional types. We employ three types of observations, flask measurements of CO2 concentrations, continuous measurements of CO2 and pointwise measurements of CO2 flux. We show that flux measurements are extremely efficient for relatively homogeneous situations but not robust against increasing or unknown complexity. Here a hybrid approach is necessary, and we recommend its use in the development of integrated carbon observing systems.

Highlights

CO2 and methane are the most important anthropogenic greenhouse gases
Quantitative Network Design (QND) is well-suited to explore the performance of observational networks of the carbon cycle
There are, a set of general findings that follow from the above-mentioned assumption of fundamental equations that govern the processes controlling the terrestrial carbon fluxes

Summary

Introduction

CO2 and methane are the most important anthropogenic greenhouse gases. Their increasing concentration is the major reason for global warming (Solomon et al, 2007). At a number of points on the globe, carbon and water fluxes are sampled directly (see, e.g. http://www.fluxnet.ornl.gov) The interpolation of these measurements to the globe (upscaling) requires external information about the uncertain spatio-temporal flux structure. The most sophisticated tools for quantifying the structure and variability of carbon fluxes are process models of the terrestrial carbon cycle like those used for the assessments of the IPCC (Solomon et al, 2007). Underlying these models is the assumption of fundamental equations that govern the processes controlling the terrestrial carbon fluxes. There is uncertainty about the state of the terrestrial biosphere at the beginning of the simulation

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Conclusion