Abstract
Feedbacks between atmospheric processes like precipitation and land surface fluxes including evapotranspiration are difficult to observe, but critical for understanding the role of the land surface in the Earth System. To quantify global surface-atmosphere feedbacks we use results of a process network (PN) applied to 251 eddy covariance sites from the LaThuile database to train a neural network across the global terrestrial surface. There is a strong land–atmosphere coupling between latent (LE) and sensible heat flux (H) and precipitation (P) during summer months in temperate regions, and between H and P during winter, whereas tropical rainforests show little coupling seasonality. Savanna, shrubland, and other semi-arid ecosystems exhibit strong responses in their coupling behavior based on water availability. Feedback couplings from surface fluxes to P peaks at aridity (P/potential evapotranspiration ETp) values near unity, whereas coupling with respect to clouds, inferred from reduced global radiation, increases as P/ETp approaches zero. Spatial patterns in feedback coupling strength are related to climatic zone and biome type. Information flow statistics highlight hotspots of (1) persistent land–atmosphere coupling in sub-Saharan Africa, (2) boreal summer coupling in the central and southwestern US, Brazil, and the Congo basin and (3) in the southern Andes, South Africa and Australia during austral summer. Our data-driven approach to quantifying land atmosphere coupling strength that leverages the global FLUXNET database and information flow statistics provides a basis for verification of feedback interactions in general circulation models and for predicting locations where land cover change will feedback to climate or weather.
Highlights
The terrestrial land surface and atmosphere are coupled through a complex set of interactions and feedbacks that determine the fluxes of mass and energy between the two systems
We focus on the land-to-atmosphere portion of land–atmosphere coupling, by investigating the directional information flow from H and LE to future states of atmospheric variables
The increase in feedback coupling between winter and summer within temperate regions coincides with a strong increase in vegetation density and greenness, represented here as the Normalized Difference Vegetation Index (NDVI)
Summary
The terrestrial land surface and atmosphere are coupled through a complex set of interactions and feedbacks that determine the fluxes of mass and energy between the two systems. An understanding of land–atmosphere feedbacks is essential for determining the regional impacts of climate variability and change on the ecosystem services humanity has come to depend, but remains a major challenge as analytical tools to quantify feedbacks have only recently been developed.[4,5,6,7,8,9,10] Feedback processes in nature are difficult to directly observe and to infer, as cause and effect relationships may become obscured or break down when a process influences itself through an intermediary,[11] as is often the case in the Earth System. This study presents direct observations of global land to atmosphere information flow through the use of a global network of surface energy flux and meteorological observations, introducing a statistical approach to characterize temporal and spatial variability in land–atmosphere coupling strength
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
