We used WRF-Chem to simulate ash transport from eruptions of Chile’s Calbuco volcano on 22–23 April 2015. Massive ash and SO₂ ejections reached the upper troposphere, and particulates transported over South America were observed over Argentina, Uruguay, and Brazil via satellite and surface data. Numerical simulations with the coupled Weather Research and Forecasting–Chemistry (WRF-Chem) model from 22 to 27 April covered eruptions and particle propagation. Chemical and aerosol parameters utilized the GOCART (Goddard Chemistry Aerosol Radiation and Transport) model, while the meteorological conditions came from NCEP-FNL reanalysis. In WRF-Chem, we implemented a more efficient methodology to determine the Eruption Source Parameters (ESP). This permitted each simulation to consider a sequence of eruptions and a time varying ESP, such as the eruption height and mass and the SO₂ eruption rate. We used two simulations (GCTS1 and GCTS2) differing in the ash mass fraction in the finest bins (0–15.6 µm) by 2.4% and 16.5%, respectively, to assess model efficiency in representing plume intensity and propagation. Analysis of the active synoptic components revealed their impact on particle transport and the Andes’ role as a natural barrier. We evaluated and compared the simulated Aerosol Optical Depth (AOD) with VIIRS Deep Blue Level 3 data and SO₂ data from Ozone Mapper and Profiler Suite (OMPS) Limb Profiler (LP), both of which are sensors onboard the Suomi National Polar Partnership (NPP) spacecraft. The model successfully reproduced ash and SO₂ transport, effectively representing influencing synoptic systems. Both simulations showed similar propagation patterns, with GCTS1 yielding better results when compared with AOD retrievals. These results indicate the necessity of specifying lower mass fraction in the finest bins. Comparison with VIIRS Brightness Temperature Difference data confirmed the model’s efficiency in representing particle transport. Overestimation of SO₂ may stem from emission inputs. This study demonstrates the feasibility of our implementation of the WRF-Chem model to reproduce ash and SO₂ patterns after a multi-eruption event. This enables further studies into aerosol–radiation and aerosol–cloud interactions and atmospheric behavior following volcanic eruptions.

The behavior of ozone gas (O₃) in the atmosphere varies according to the region of the globe. Its formation occurs mainly in the tropical stratosphere through the photodissociation of molecular oxygen with the aid of the incidence of ultraviolet solar radiation. Still, the highest concentrations of O₃ content are found in high-latitude regions (poles) due to the Brewer–Dobson circulation, a large-scale circulation that takes place from the tropics to the pole in the winter hemisphere. This work presents a multi-instrumental analysis at two Brazilian sites, a subtropical one (Santa Maria – 29.72° S, 53.41° W) and an equatorial one (Natal – 5.4° S, 35.4° W), to investigate ozone distributions in terms of vertical profiles (2002–2020) and total abundance in terms of total columns of ozone (1979–2020). The study is based on the use of ground-based and satellite observations. Ozone profiles over Natal, from the ground up to the mesosphere, are obtained by radiosonde experiments (0–30 km) in the framework of the SHADOZ program and by satellite measurements from the SABER instrument (15–60 km). This enabled the construction of a continuous time series for ozone, including monthly values and climatological trends. There is a good agreement between the two measurements in the common observation layer, mainly for altitudes above 20 km. Below 20 km, SABER ozone profiles showed high variability and overestimated ozone mixing ratios by over 50 %. Dynamic and photochemical effects can interfere with O₃ formation and distribution along higher latitudes through the Brewer–Dobson circulation. The measurements of the total ozone columns used are in good agreement with each other (TOMS/OMI × Dobson for Natal and TOMS/OMI × Brewer for Santa Maria) in time and space, in line with previous studies for these latitudes. Wavelet analysis was used over 42 years. The investigation revealed a significant annual cycle in both data series for both sites. The study highlighted that the quasi-biennial oscillation (QBO) plays a significant role in the variability of stratospheric ozone at the two study sites – Natal and Santa Maria. The QBO's contribution was found to be stronger at the Equator (Natal) than at the subtropics (Santa Maria). Additionally, the study showed that the 11-year solar cycle also has a significant impact on ozone variability at both locations. Given the study latitudes, the ozone variations observed at the two sites showed different patterns and amounts. Only a limited number of studies have been conducted on stratospheric ozone in South America, particularly in the region between the Equator and the subtropics. The primary aim of this work is to investigate the behavior of stratospheric ozone at various altitudes and latitudes using ground-based and satellite measurements in terms of vertical profiles and total columns of ozone.

O trabalho proposto tem como intuito avaliar as condições sinóticas durante o evento de queimadas na região amazônica no mês de agosto de 2019 o qual acabou acarretando no transporte de particulados para a região sudeste, impactando diretamente na cidade de São Paulo no dia 19 transformando o dia em noite. Para a avaliação, foi utilizado os dados de reanálise do ERA5 juntamente aos dados modelo HYSPLIT com objetivo de analisar a trajetória das parcelas de ar durante o evento. A partir das avaliações observou-se a passagem de um sistema frontal o qual teve como função a convergência de umidade e escoamento de ventos sobre a região de São Paulo favorecendo o desenvolvimento de nebulosidade. Além disso, o aumento de particulados ao longo da atmosfera pode ter contribuido como núcleo de condensação, podendo assim favorecer o aumento considerável de nuvens escuras durante o perı́odo da tarde no municı́pio impactando diretamente na radiação refletida dando um aspecto noturno para a cidade.

The Weather Research and Forecasting (WRF) model is used to study the transport of a passive scalar plume, representing smoke from biomass burning in South America (SA). In this context, the Mellor–Yamada–Nakanishi–Niino (MYNN), Yonsei University (YSU), and Bougeault-Lacarrere (BouLac) Planetary Boundary-Layer (PBL) schemes were utilized. A total of three simulations were conducted, one for each PBL scheme, starting on August 15, 2019, and ending on August 20, 2019. This period was characterized by a high concentration of smoke, which were transported to the southern and southeastern regions of South America. During this period, the direct impact of these particulates was observed in the São Paulo Metropolitan Area (SPMA). To determine the positions of the passive tracers, data from the Fire Information for Resource Management System (FIRMS) were used to identify the regions with the highest Fire Radiative Power (FRP) during the study period. Based on this analysis, three locations in different areas were selected. To analyze the transport, synoptic fields were examined during the study period to provide a better description of the atmospheric dynamics. On the mesoscale, the impact of diffusivity was assessed for each PBL scheme. For validation, surface data from the Light Detection and Ranging (LiDAR) system, located in the São Paulo region was utilized. It was observed that one of the tracers reached the SMPA in all three simulations. However, when analyzing the other tracers, the BouLac scheme failed to transport the particulates to this region. Dynamically, the low-level jet played an active role in transporting the tracers across the southern part of domain and subsequently toward the southeastern region.

Large Eddy Simulation (LES) have been employed to investigate turbulent flows. In atmospheric turbulence, this methodology is widely used and, sometimes is complementary to field experiments, leading a more detailed about turbulent flow. In this work a LES model was utilized to describe the influence exerted by a hot plume, emitted for a thermal power-plant in the atmospheric flow in the planetary boundary-layer.

This single high-impact case study investigates the impact of planetary boundary layer (PBL) representation on long-range transport of Amazon fire smoke that reached the Metropolitan Area of São Paulo (MASP) from 15 to 20 August 2019, using the WRF model to compare three PBL schemes (MYNN 2.5, YSU, and BouLac) and three source-tagged tracers. The simulations are evaluated against MODIS-derived aerosol optical depth (AOD), the Light Detection and Ranging (LiDAR) time–height curtain over MASP, and HYSPLIT forward trajectories. Transport is diagnosed along the source-to-MASP pathway using six-hourly cross-sections and two integrative metrics: the projected mean wind in the 700–600 hPa layer and the vertical moment of tracer mass above the boundary layer. Outflow and downwind impact are strongest when a persistent reservoir between 2 and 4 km coexists with projected winds for several hours. In this episode, MYNN maintains an elevated 2–5 km transport layer and matches the observed arrival time and altitude, YSU yields a denser but delayed column, and BouLac produces discontinuous pulses with reduced coherence over the city. A negatively tilted trough, jet coupling, and a nearly stationary front establish a northwest-to-southeast corridor consistent across model fields, trajectories, and satellite signal. Seasonal robustness should be assessed with multi-event, multi-model analyses.