High-quality atmospheric CO2 measurements are sparse across the Amazon rainforest. Yet they are important to better understand the variability of sources and sinks of CO2. And indeed, one of the reasons ATTO was built was to obtain long-term measurements in such a critical region.
ATTO scientists first installed measurement systems for CO2 in March 2012 at the 81 m walk-up tower at ATTO. Since then, inlets continuously collect air at five heights (4 m, 24 m, 38 m 53 m and 79 m). Therefore, they measure at the ground, within the forest canopy, and above it. Santiago Botía and his colleagues now published the first 6 years of continuous, high-precision measurements of atmospheric CO2 at ATTO. Based on this 6-year long record, they were to gain insights into some of the processes that affect trace gases in the Amazon rainforest.
For their study, they looked at half-hour data during daytime, when the atmosphere is generally well mixed. At nighttime, there is often intense atmospheric stratification. This means that local signals (like from small stream valleys or even single trees) could easily dominate the measured signal. That would make it impossible to learn more about larger-scale processes.
Seasonal and inter-annual variability of CO2
Comparing data to model simulations
Ramsay et al. developed a new model to assess nitrogen exchange between atmosphere and biosphere based on observations at ATTO. This model includes parameters controlling both nitrogen deposition and emissions in tropical forests.
Ramsay et al. measured inorganic trace gases such as ammonia and nitric acid and aerosols in the dry season at ATTO. They are to serve as baseline values for their concentration and fluxes in the atmosphere and are a first step in deciphering exchange processes of inorganic trace gases between the Amazon rainforest and the atmosphere.
Pfannerstill et al. compared VOC emissions at ATTO between a normal year and one characterized by a strong El Nino with severe droughts in the Amazon. The did not find large differences, except in the time of day that the plants release the VOCs. They published their results in the journal Frontiers in Forest and Global Change.