Using observations from the new ATTO-Campina site and LES modeling to study cloud organization and the shallow-to-deep transition

We first present a summary of results from ATTO-Campina, a new permanent observational site deployed in central Amazon, about 4 km from the ATTO towers. Those results are then complemented by preliminary modeling studies about shallow cumulus clouds organization. Operational since 2020, ATTO-Campina focuses on characterizing atmospheric, cloud and rainfall properties through remote sensing. The overarching goal is to provide continuous, complementary measurements to the ATTO towers, addressing the rainforest’s complex and unique gas-aerosol-cloud-precipitation dynamics. Previous studies have highlighted the critical role of convective clouds in the new particle formation (NPF) process, driven by the vertical transport of gasses and aerosol particles. Using a 3.5-year dataset, we classified convective clouds into three types: shallow cumulus (ShCu), congestus (Con) or (Deep) clouds. The shallow-to-deep transition takes about three hours, starting with ShCu formation at 11:00 local time. The accumulated rainfall peak follows at about 16:00 local time. Only weak downdrafts are present in the upper troposphere where NPF takes place, while strong downdrafts are mostly limited to heights below 5 km. Con and Deep convective days have higher concentrations of ultrafine aerosol and lower concentration of accumulation-mode particles compared to ShCu. Convective clouds also significantly modify gas mixing ratios, with a distinct background concentration of CO₂ for different cloud types. In addition, deep convective clouds considerably increase the O₃ mixing ratio close to the surface. Our results showcase the added detail achieved by integrating data from the ATTO towers and ATTO-Campina sites. Together, these sites support a better understanding of the interconnected gas-aerosol-cloud-precipitation processes in the Amazon and their evolution under the influence of climate change. On the modeling side, we provide preliminary results from 100-m resolution simulations of shallow cumulus cloud fields. The cloud fields are analyzed in terms of their organization indexes and the role of aerosols is quantified on changes of those indexes. Overall, we will discuss the characteristcs of shallow and deep convection in the Amazon, as well as how the organization indexes can be used to quantify the shallow-to-deep transition.