Jorge Saturno

Amazon boundary layer aerosol concentration sustained by vertical transport during rainfall

The nucleation of atmospheric vapours is an important source of new aerosol particles that can subsequently grow to form cloud condensation nuclei in the atmosphere. Most field studies of atmospheric aerosols over continents are influenced by atmospheric vapours of anthropogenic origin (for example, ref. 2) and, in consequence, aerosol processes in pristine, terrestrial environments remain poorly understood. The Amazon rainforest is one of the few continental regions where aerosol particles and their precursors can be studied under near-natural conditions, but the origin of small aerosol particles that grow into cloud condensation nuclei in the Amazon boundary layer remains unclear. Here we present aircraft- and ground-based measurements under clean conditions during the wet season in the central Amazon basin. We find that high concentrations of small aerosol particles (with diameters of less than 50 nanometres) in the lower free troposphere are transported from the free troposphere into the boundary layer during precipitation events by strong convective downdrafts and weaker downward motions in the trailing stratiform region. This rapid vertical transport can help to maintain the population of particles in the pristine Amazon boundary layer, and may therefore influence cloud properties and climate under natural conditions.

Efflorescence upon humidification? X‐ray microspectroscopic in situ observation of changes in aerosol microstructure and phase state upon hydration

The phase and mixing state of atmospheric aerosols is a central determinant of their properties and thus their role in atmospheric cycling and climate. Particularly, the hygroscopic response of aerosol particles to relative humidity (RH) variation is a key aspect of their atmospheric life cycle and impacts. Here we applied X-ray microspectroscopy under variable RH conditions to internally mixed aerosol particles from the Amazonian rain forest collected during periods with anthropogenic pollution. Upon hydration, we observed substantial and reproducible changes in particle microstructure, which appear as mainly driven by efflorescence and recrystallization of sulfate salts. Multiple solid and liquid phases were found to coexist, especially in intermediate humidity regimes. We show that X-ray microspectroscopy under variable RH is a valuable technique to analyze the hygroscopic response of individual ambient aerosol particles. Our initial results underline that RH changes can trigger strong particle restructuring, in agreement with previous studies on artificial aerosols.

Black and brown carbon over central Amazonia: Long-term aerosol measurements at the ATTO site

The Amazon rain forest is a sensitive ecosystem experiencing the combined pressures of progressing deforestation and climate change. Its atmospheric conditions oscillate between biogenic and biomass burning (BB) dominated states. The Amazon further represents one of the few remaining continental places where the atmosphere approaches pristine conditions during occasional wet season episodes. The Amazon Tall Tower Observatory (ATTO) has been established in central Amazonia to investigate the complex interactions between the rain forest ecosystem and the atmosphere. Physical and chemical aerosol properties have been analyzed continuously since 2012. This paper provides an