Atmospheric Carbon and Land-Atmosphere Interactions Research

Description

Carbon and water cycles are tightly coupled in terrestrial ecosystems, giving rise to ecosystem-atmosphere feedbacks that affect surface energy forcing, clouds, and atmospheric CO2 concentrations. Understanding ecosystem influences on atmospheric conditions and CO2 concentrations, and accurately representing the effects of CO2 concentrations on radiative forcing, are critical to predicting climate change due to anthropogenic CO2 emissions and land use change. We will present an overview of the Atmospheric System Research Scientific Focus Area at Lawrence Berkeley National Laboratory (LBNL ASR SFA) on atmospheric carbon and land-atmosphere interactions. Our main goal is to better understand ecosystem-climate interactions, and especially those mediated by carbon, water, and energy exchanges. This work bridges spatial scales from the plot to the region, using a combination of measurements and models meet the following objectives: • Quantify and analyze atmospheric sources, sinks, and concentrations of CO2 and other carbon cycle tracers in the continental U.S., Arctic, and Amazonia (ARM SGP, NSA, and GOAmazon sites, respectively). We are making a comprehensive set of carbon cycle measurements (with support from ARM, ASR, and TES). • Analyze observed responses of surface CO2, water, and energy fluxes to diffuse radiation from aerosols and clouds, and improve land model representations of these responses (Task 2) • Determine impacts of climate extremes and land management on observed surface CO2, water, and energy fluxes in temperate and tropical systems, and improve model representation of these impacts. • Reduce model precipitation biases through improved representation of land-atmosphere coupling in land surface models on diurnal through synoptic time-scales • Improve climate model prediction of CO2 and CH4 surface radiative forcing, by comparing predicted surface radiative forcing with well-calibrated observations over diurnal to decadal timescales. We will present some highlights of our work, including: The first empirical confirmation of radiative forcing from observed increases in atmospheric CO2 (30 ppm from 2000-2010); application of a novel tracer (carbonyl sulfide) to empirically partition ecosystem fluxes to GPP and respiration; and revised understanding of the effect of the diffuse-direct radiation GPP and land surface fluxes of CO2, water, and energy.