New Publication: Air turbulence characteristics in and above the Amazon rainforest canopy

One of our major goals at ATTO is understanding how the Amazon rainforest interacts with the atmosphere above. This includes studying how the characteristics of the air change within and above the tree canopy in terms of atmospheric turbulence. The strength of the wind and the thickness of the canopy determine, among other things, how well the air can mix and to what degree gases from the atmosphere may reach the forest floor and vice versa.

In a new study, the scientists were looking into these processes at two Amazon sites, including ATTO. They found that the lowermost air-layer from the forest floor to about half the tree height is largely decoupled from the air in the upper part of the canopy and above. That is an important finding, as this process may limit the extent to which plant-emitted gases are transported out of the forest canopy into the atmosphere above.
Raoni Aquino and co-authors now published their findings in a new study called “Air turbulence characteristics at multiple sites in and above the Amazon rainforest canopy” in the journal Agricultural and Forest Meteorology, Volume 260-261.

New Publication: Variability of black and brown carbon concentrations

We are currently in the middle of the dry season in the central Amazon basin, where ATTO is located. This time of year is always characterized by lots of biomass burnings, both natural and anthropogenic. Fires produce aerosols, such as black and brown carbon. But the situation isn’t the same every year.

Our researchers studied the concentration of light-absorbing aerosol particles at ATTO over a 5-year period from 2012 to 2017. They found that the aerosol concentration increased significantly during the El Niño of 2015-2016. During that time, the dry season lasted longer than normal and forest and agricultural fires occurred much more frequently compared to other years. The fires produce large amounts of black and brown carbon. These are able to absorb radiation, which has two important effects: firstly, it warms the atmosphere, and secondly, less radiation is able to reach the canopy and forest floor, thus affecting the primary production of the forest. That means that a climatic shift to warmer and drier conditions and potentially stronger and more frequent El Niños could affect the Amazon rainforest in the future.

First-author Jorge Saturno just published the study in Atmospheric Chemistry and Physics (ACP) Issue 18. It is available Open Access and thus freely available for everyone.

New Publication: Aerosol composition and cloud dynamics

The properties and dynamics of clouds are strongly dependent on the types and amounts of aerosol particles in the atmosphere. They act as so-called cloud condensation nuclei as they initiate the formation of cloud droplets. Therefore, it is crucial to gain a sound understanding of the emission patterns, properties, and seasonal variability of aerosols in relation to the cloud life cycles. In order to achieve this goal, our aerosol group was able to record such data at ATTO. Over the course of a full year, they continuously measured aerosols and their properties in the atmosphere at the 80 m tower. Thus, they created the first such long-term record in the Amazon.

The results of the study were published in two parts; the first was released in 2016 and focused on the parameterization of the aerosol properties. This provides the scientific community with input for models to better predict atmospheric cycling and future climate. Because clouds are such a vital and highly complex component of the climate system, it is important for models to get them “right” in order to make reliable predictions.

In this newly published second part of the study, the authors focused on defining the most distinctive states of aerosol composition and associated cloud formation conditions in the ATTO region. They distinguished between four separate regimes that alternate throughout the year. For example, they discovered that the atmosphere is practically pristine during certain episodes in the wet season (from March to May), with no detectable influence of pollution. However, throughout the rest of the year, “foreign” aerosols arrive at the site in varying amounts. They include natural aerosol particles such as Saharan dust, but also pollutants such as smoke from biomass burning (wildfires and much more often deforestation fires) within the Amazon or even in Africa.

Part 1 and Part 2 of this study were published by first author Mira Pöhlker in Atmospheric Chemistry and Physics (ACP) Issues 16 and 18. They are available Open Access and thus freely available for everyone.

New publication: African volcanic emissions reach Amazon

One of the objectives of ATTO is to study the long-range transport of particles, such as sulfate, across the Atlantic to the Amazon rainforest and to better understand atmospheric cycling.

A good opportunity for that arose in 2014. Some of the most active volcanoes worldwide, the Nyamuragira and Mount Nyiragongo volcanoes in Congo in Central Africa, erupted violently. During this eruption, they emitted a lot of sulfur dioxide (SO2) into the atmosphere. This gas that is later converted to sulfate particles by oxidation. Usually, these particles are diluted in the atmosphere as they mix with other particles. It thus becomes difficult to distinguish them far away from their source. However, the emissions of 2014 were so strong that the sulfate particles originating from the volcanic gas were observed over the Amazon rainforest by ground-based instruments at our ATTO site (specifically at the 80 m tall triangular mast) and by aircraft measurements (during the ACRIDICON-CHUVA campaign). This observation is now being used by ATTO scientists as a case study to understand how gas and particle emissions from Africa are transported over the Atlantic Ocean and reach the Amazon Basin.

For scale, the volcanoes in Congo are almost 10,000 km away from ATTO, and it took the particles around 2 weeks to bridge that distance!

The full study was just published in Atmospheric Chemistry and Physics (ACP) Issue 18 by first author Jorge Saturno. It is available Open Access and thus freely available for everyone.

 

New publication on aerosols in the Amazon

Scientists from our Aerosol group published a new “Long-term study on coarse mode aerosols in the Amazon rainforest with the frequent intrusion of Saharan dust plumes”.

They analyzed the coarse fraction of aerosols (those that are at least 1 micrometer in diameter) every 5 minutes for over 3 years and were surprised to find that over this period the size and abundance of these “large” aerosol particles remained fairly constant. In contrast, the smaller aerosols are heavily influenced by the seasonal occurrence of smoke from fires. This coarse fraction, however, is mainly comprised of aerosols derived from the rainforest itself (such as pollen). That pattern only changes during the wet season (December through April), when Saharan dust, sea salt particles from the Atlantic and smoke from fires in Africa episodically make their way to the Amazon. Especially in February and March, pulses of African aerosols become so frequent they are the norm rather than the exception. Our scientists then used these data to estimate how much dust is deposited in the ATTO region each year: 5-10 kg per hectare, or 0.5-1 g per square meter.

You can read the full study by lead author Daniel Moran-Zuloaga in Atmospheric Chemistry and Physics Issue 18. It is published Open Access and thus freely available online. The data set is also available for further analysis (see publication for details)!