Postdoc Position at the Atmospheric Physics Laboratory at the University of Sao Paulo

Introduction

Amazonian New Particle Formation: Resolving the Contributions of Local Formation, Primary Biological Sources and Atmospheric Transport

Cloud droplet formation and growth depend on aerosol particles acting as cloud condensation nuclei. Aerosol can be transported from natural sources or locally produced by primary biological aerosol particles and/or by gas oxidation, clustering, and condensation to form and grow new particles (Pöschl et al, 2010, Kulmala et. al, 2004). The new particle formation process could be responsible for up to 70% of ultrafine particles. New particle formation near the surface in Boreal Forests is well understood. It strongly depends on the gaseous sulfuric acid (Kulamala et. al, 2013). However, in pristine regions such as tropical forests, where sulfate concentrations are extremely low, the mechanisms driving new particle formation remain poorly understood. These events have traditionally been attributed primarily to particle transport from the upper troposphere rather than to local formation processes (Wang et al., 2016). More recently, however, studies have shown that pristine forests can experience new particle formation following rainfall events, largely due to increases in ozone concentrations and enhanced oxidation of volatile organic compounds (Machado et al., 2024).

Multiphase chemistry is fundamental to Earth system modeling. The size threshold separating gas-phase molecules from particulate matter is approximately 1 nanometer. Atmospheric aerosols are commonly classified into nucleation, Aitken, accumulation, and coarse modes according to their size distributions. Cloud droplets typically have diameters exceeding ~10 μm. This study focuses on the features related to the transformation from gas to particle, the gas clustering processes, and condensation growing up to coagulation and scavenging and on the aerosol and cloud interaction. On a planet undergoing rapid climate change and experiencing increasing anthropogenic modification of tropical forests, it is essential to understand the physicochemical processes involved in particle formation and their subsequent growth into cloud condensation nuclei. Developing the capability to accurately represent these processes in models is crucial for understanding and predicting how tropical forests will respond to and influence global climate change.

This proposal builds on measurement campaigns at the ATTO site aimed at quantifying new particle formation arising from multiple processes. Observations will be conducted both as part of continuous measurements at ATTO and during dedicated field campaigns, including AMAZE27 (Amazon Experiment Campaign 2027) and, pending approval, ATKO (Amazon Tethered Kite Observatory). The project will further benefit from new instrumentation, such as the LIDAR system currently being acquired by ATTO-INCT.

The main objective of this post-doc project is to characterize and quantify the new particle formation in the early morning, during rain events and during stable atmosphere for the different formation processes.