New Publication: Footprint region of ATTO

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).

Wind direction and speed mainly shape the location and size of the footprint region. At ATTO, this largely depends on the seasonal shift of the intertropical convergence zone (ITCZ). The authors found a northeasterly path during the wet season, with the air moving largely over pristine rainforest. During the dry season, the air takes a more southeasterly path within the influence of agricultural areas.Secondly, they further characterized this ATTO footprint area. They looked at it in terms of climate, land cover and -use, fire regimes and present-day and future deforestation scenarios. They placed a large emphasis on human-caused transformations in Amazonia and how this will influence data observed at ATTO. While it is still possible to study unperturbed rainforest today, they conclude that this will likely decrease in the future. In contrast, atmospheric signals from human-made and climate-change-related forest perturbations will increase in frequency and intensity.