Christopher Pöhlker and co-authors published an extensive new paper, characterizing the footprint region of ATTO. They hope that fellow researchers in the Amazon region can use this publication as resource and reference work to embed ATTO observations into a larger context of Amazonian deforestation and land use change. Pöhlker et al. published the paper Open Access in Atmospheric Chemistry and Physics Volume 19.
In their study, they used backward trajectories to first define the ATTO footprint region. With this modeling approach, you can trace air masses in the atmosphere back along their presumed transport path to ATTO. Because the source regions of observed trace gases and aerosols might be thousands of kilometers away, they did not necessarily trace it all the way back. Instead, they defined the region on the South American continent over which the atmosphere interacts most intensely with the land surface below. Such interactions might be the exchange of gases, taking up water vapor or releasing it through precipitation, or altering the aerosol content (e.g. washing out of aerosols with rain or taking up new aerosols that are dispersed into the atmosphere).
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In a new study, Marco A. Franco and his colleagues analyzed when and under what conditions aerosols grow to a size relevant for cloud formation. Such growth events are relatively rare in the Amazon rainforest and follow and pronounced diurnal and seasonal cycles. The majority take place during the daytime, and during the wet season. But the team also discovered a few remarkable exceptions.
It is long known that aerosols, directly and indirectly, affect clouds and precipitation. But very few studies have focused on the opposite: the question of how clouds modify aerosol properties. Therefore, Luiz Machado and his colleagues looked into this process at ATTO. Specifically, they studied how weather events influenced the size distribution of aerosol particles.
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