Amazonian aerosol size distributions in a lognormal phase space: characteristics and trajectories

Autor(es)

Unfer, Gabriela ; Machado, Luiz ; Artaxo, Paulo ; Franco, Marco ; Kremper, Leslie ; Poehlker, Mira ; Poeschl, Ulrich ; Poehlker, Christopher

• Tipo de documento: Artigo Científico
• Fonte: Atmospheric Chemistry and Physics; v. 24, n. 6, p. 14-pg., 2024-04-02.

Resumo

This study introduces a first glance at Amazonian aerosols in the N - D g - sigma phase space. Aerosol data, measured from May 2021 to April 2022 at the Amazon Tall Tower Observatory (ATTO), were fitted by a multi-modal lognormal function and separated into three modes: the sub-50 nm, the Aitken (50-100 nm), and the accumulation modes. The fit results were then evaluated in the N - D g - sigma phase space, which represents a three-dimensional space based on the three lognormal fit parameters. These parameters represent, for a given mode i , the number concentration ( N i ), the median geometric diameter ( D g , i ), and the geometric standard deviation ( sigma i ). Each state of a particle number size distribution (PNSD) is represented by a single dot in this space, while a collection of dots shows the delimitation of all PNSD states under given conditions. The connections in ensembles of data points show trajectories caused by pseudo-forces, such as precipitation regimes and vertical movement. We showed that all three modes have a preferential arrangement in this space, reflecting their intrinsic behaviors in the atmosphere. These arrangements were interpreted as volumetric figures, elucidating the boundaries of each mode. Time trajectories in seasonal and diurnal cycles revealed that fits with the sub-20 nm mode are associated with rainfall events that happen in the morning and in the afternoon. But in the morning they grow rapidly into the Aitken mode, and in the afternoon they remain below 50 nm. Also, certain modes demonstrated well-defined curves in the space, e.g., the seasonal trajectory of the accumulation mode follows an ellipsoid, while the diurnal cycle of the sub-50 nm mode in the dry season follows a linear trajectory. As an effect of the precipitation on the PNSDs and vice versa, N and D g were found to increase for the sub-50 nm mode and to decrease for the Aitken and accumulation modes after the precipitation peak. Afternoons with precipitation were preceded by mornings with larger particles of the accumulation mode, whose D g was similar to 10 nm larger than in days without precipitation. Nevertheless, this large D g in the morning seems to influence subsequent rainfall only in the dry season, while in the wet season both N and D g seem to have the same weight of influence. The observed patterns of the PNSDs in the N - D g - sigma phase space showed to be a promising tool for the characterization of atmospheric aerosols, to contribute to our understanding of the main processes in aerosol-cloud interactions, and to open new perspectives on aerosol parameterizations and model validation. (AU)

• Processo FAPESP: 21/03547-7 - Interações entre aerossóis e eventos de tempo na Amazônia
• Beneficiário: Gabriela Rosalino Unfer
• Modalidade de apoio: Bolsas no Brasil - Mestrado
• Processo FAPESP: 22/07974-0 - Efeitos sinergéticos das mudanças climáticas e do uso do solo nas fontes e sumidouros de carbono na Amazônia
• Beneficiário: Luiz Augusto Toledo Machado
• Modalidade de apoio: Auxílio à Pesquisa - Programa de Pesquisa sobre Mudanças Climáticas Globais - Temático
• Processo FAPESP: 22/01780-9 - Detecção da formação de novas partículas no ATTO: avaliação do efeito convectivo da nuvem
• Beneficiário: Gabriela Rosalino Unfer
• Modalidade de apoio: Bolsas no Exterior - Estágio de Pesquisa - Mestrado