Identifying CO2 advection on a hill slope using information flow

Abstract

In hilly terrain affected by drainage flow, the horizontal advection of CO 2 makes it difficult to accurately observe the net ecosystem exchange of CO 2 by the eddy covariance technique. Downslope drainage can result in an overestimation of respiration at the bottom of a hill slope and an underestimation at the top, resulting in discrepancies among different flux corrections using filters based on the friction velocity, light response curve, and timing of advection. Vertical profiles of the CO 2 concentration from the ground to above the canopy were measured along with above-canopy EC flux measurements at the top and bottom of a hill slope at the Gwangneung KoFlux sites from 2008 to 2010. To infer the timing, direction, temporal scale, and structure of CO 2 advection from uphill to downhill, we constructed an information flow dynamical process network (DPN) based on the observed multi-level CO 2 concentrations. A sitespecific quality control filter was developed to eliminate data strongly affected by CO 2 advection, which identifies the observations when strong downslope information flow exists in the DPN. This site-specific filter considerably reduced the discrepancies among different traditional flux corrections. This research provides a method for the general characterization of advection using information flow, and application of the method as a site-specific filter for eddy covariance observations in hilly and complex terrain.

Process connectivity in a naturally prograding river delta

“…Similarly, a study by Kang et al . [] used information theory to identify CO 2 advection on a hillslope and found good agreement between information flow and physical advection.…”

Robust observations of land-to-atmosphere feedbacks using the information flows of FLUXNET

“…11 Information flow statistics are a robust and mature method for delineating PNs, and have been previously applied to the direct and explicit measurement of feedback between the land surface and atmosphere using flux tower observations. [35][36][37][38][39] PNs have been shown to accurately diagnose interactions between turbulent fluxes and the atmosphere in ecohydrological systems, [35][36][37]40 and have accurately described functional differences between starkly diverse land surface ecosystems at continental scales. 35,41,42 This paper's choice of Transfer Entropy to delineate PNs 43 is ideal to measure directional, scale-specific, and nonlinear couplings that characterize land-to-atmosphere feedbacks.…”

New gap-filling and partitioning technique for H<sub>2</sub>O eddy fluxes measured over forests

“…Compared to the GDK site, the GCK site is in a lower area and is a flat, plantation forest with the dominant species of Abies holophylla (approximately 80 years old) with a mean canopy height of ∼ 23 m and a maximum LAI of ∼ 8 m 2 m −2 in June. Further descriptions of the sites can be found in Kim et al (2006) and Kang et al (2017).…”

“…This depends on data availability, temporal scale of the process, and ecosystem state change. Those processes require extra care in measurement in complex mountainous terrain (e.g., van Gorsel et al, 2009;Kang et al, 2017).…”