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.