GREGORI DE ARRUDA MOREIRA

GREGORI DE ARRUDA MOREIRA

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Influence of a biomass-burning event in PM2.5 concentration and air quality
2021 - MOREIRA, GREGORI de A.; ANDRADE, IZABEL da S.; CACHEFFO, ALEXANDRE; LOPES, FABIO J. da S.; YOSHIDA, ALEXANDRE C.; GOMES, ANTONIO A.; SILVA, JONATAN J. da; LANDULFO, EDUARDO
Severe biomass burning (BB) events have become increasingly common in South America in the last few years, mainly due to the high number of wildfires observed recently. Such incidents can negatively influence the air quality index associated with PM2.5 (particulate matter, which is harmful to human health). A study performed in the Metropolitan Area of São Paulo (MASP) took place on selected days of July 2019, evaluated the influence of a BB event on air quality. Use of combined remote sensing, a surface monitoring system and data modeling and enabled detection of the BB plume arrival (light detection and ranging (lidar) ratio of (50 ± 34) sr at 532 nm, and (72 ± 45) sr at 355 nm) and how it affected the Ångström exponent (>1.3), atmospheric optical depth (>0.7), PM2.5 concentrations (>25 µg.m−3), and air quality classification. The utilization of high-order statistical moments, obtained from elastic lidar, provided a new way to observe the entrainment process, allowing understanding of how a decoupled aerosol layer influences the local urban area. This new novel approach enables a lidar system to obtain the same results as a more complex set of instruments and verify how BB events contribute from air masses aloft towards near ground ones.
Retrieval of optical and microphysical properties of transported Saharan dust over Athens and Granada based on multi-wavelength Raman lidar measurements
2019 - SOUPIONA, O.; SAMARAS, S.; ORTIZ-AMEZCUA, P.; BOCKMANN, C.; PAPAYANNIS, A.; MOREIRA, G.A.; BENAVENT-OLTRA, J.A.; GUERRERO-RASCADO, J.L.; BEDOYA-VELASQUEZ, A.E.; OLMO, F.J.; ROMAN, R.; KOKKALIS, P.; MYLONAKI, M.; ALADOS-ARBOLEDAS, L.; PAPANIKOLAOU, C.A.; FOSKINIS, R.
In this paper we extract the aerosol microphysical properties for a collection of mineral dust cases measured by multi-wavelength depolarization Raman lidar systems located at the National Technical University of Athens (NTUA, Athens, Greece) and the Andalusian Institute for Earth System Research (IISTA-CEAMA, Granada, Spain). The lidar-based retrievals were carried out with the Spheroidal Inversion eXperiments software tool (SphInX) developed at the University of Potsdam (Germany). The software uses regularized inversion of a two-dimensional enhancement of the Mie model based on the spheroid-particle approximation with the aspect ratio determining the particle shape. The selection of the cases was based on the transport time from the source regions to the measuring sites. The aerosol optical depth as measured by AERONET ranged from 0.27 to 0.54 (at 500 nm) depending on the intensity of each event. Our analysis showed the hourly mean particle linear depolarization ratio and particle lidar ratio values at 532 nm ranging from 11 to 34% and from 42 to 79 sr respectively, depending on the mixing status, the corresponding air mass pathways and their transport time. Cases with shorter transport time showed good agreement in terms of the optical and SphInXretrieved microphysical properties between Athens and Granada providing a complex refractive index value equal to 1.4 + 0.004i. On the other hand, the results for cases with higher transport time deviated from the aforementioned ones as well as from each other, providing, in particular, an imaginary part of the refractive index ranging from 0.002 to 0.005. Reconstructions of two-dimensional shape-size distributions for each selected layer showed that the dominant effective particle shape was prolate with diverse spherical contributions. The retrieved volume concentrations reflect overall the intensity of the episodes.
Analyzing the atmospheric boundary layer using high-order moments obtained from multiwavelength lidar data
2019 - MOREIRA, GREGORI de A.; LOPES, FABIO J. da S.; GUERRERO-RASCADO, JUAN L.; SILVA, JONATAN J. da; GOMES, ANTONIO A.; LANDULFO, EDUARDO; ALADOS-ARBOLEDAS, LUCAS
The lowest region of the troposphere is a turbulent layer known as the atmospheric boundary layer (ABL) and characterized by high daily variability due to the influence of surface forcings. This is the reason why detecting systems with high spatial and temporal resolution, such as lidar, have been widely applied for researching this region. In this paper, we present a comparative analysis on the use of lidar-backscattered signals at three wavelengths (355, 532 and 1064 nm) to study the ABL by investigating the highorder moments, which give us information about the ABL height (derived by the variance method), aerosol layer movement (skewness) and mixing conditions (kurtosis) at several heights. Previous studies have shown that the 1064 nm wavelength, due to the predominance of particle signature in the total backscattered atmospheric signal and practically null presence of molecular signal (which can represent noise in high-order moments), provides an appropriate description of the turbulence field, and thus in this study it was considered a reference. We analyze two case studies that show us that the backscattered signal at 355 nm, even after applying some corrections, has a limited applicability for turbulence studies using the proposed methodology due to the strong contribution of the molecular signature to the total backscatter signal. This increases the noise associated with the high-order profiles and, consequently, generates misinformation. On the other hand, the information on the turbulence field derived from the backscattered signal at 532 nm is similar to that obtained at 1064 nm due to the appropriate attenuation of the noise, generated by molecular component of backscattered signal by the application of the corrections proposed.
Study of the planetary boundary layer by microwave radiometer, elastic lidar and Doppler lidar estimations in Southern Iberian Peninsula
2018 - MOREIRA, GREGORI de A.; GUERRERO-RASCADO, JUAN L.; BRAVO-ARANDA, JUAN A.; BENAVENT-OLTRA, JOSE A.; ORTIZ-AMEZCUA, PABLO; ROMAN, ROBERTO; BEDOYA-VELASQUEZ, ANDRES E.; LANDULFO, EDUARDO; ALADOS-ARBOLEDAS, LUCAS
The Planetary Boundary Layer (PBL) is a relevant part of the atmosphere with a variable extension that clearly plays an important role in fields like air quality or weather forecasting. Passive and active remote sensing systems have been widely applied to analyze PBL characteristics. The combination of different remote sensing techniques allows obtaining a complete picture on the PBL dynamic. In this study, we analyze the PBL using microwave radiometer, elastic lidar and Doppler lidar data. We use co-located data simultaneously gathered in the framework of SLOPE-I (Sierra Nevada Lidar aerOsol Profiling Experiment) campaign at Granada (Spain) during a 90- day period in summer 2016. Firstly, the PBL height (PBLH) obtained from microwave radiometer data is validated against PBLH provided by analyzing co-located radiosondes, showing a good agreement. In a second stage, active remote sensing systems are used for deriving the PBLH. Thus, an extended Kalman filter method is applied to data obtained by the elastic lidar while the vertical wind speed variance method is applied to the Doppler lidar. PBLH′s derived by these approaches are compared to PBLH retrieved by the microwave radiometer. The results show a good agreement among these retrievals based on active remote sensing in most of the cases, although some discrepancies appear in instances of intense PBL changes (either growth and/or decrease).
Sources and physicochemical characteristics of submicron aerosols during three intensive campaigns in Granada (Spain)
2018 - AGUILA, A. del; SORRIBAS, M.; LYAMANI, H.; TITOS, G.; OLMO, F.J.; ARRUDA-MOREIRA, G.; YELA, M.; ALADOS-ARBOLEDAS, L.
Aerosol particles in the submicron range and their physicochemical characteristics were investigated for the first time in Granada, southeastern Iberian Peninsula, during three intensive campaigns. The physical and chemical characteristics were analysed during two spring campaigns and one autumn campaign. New particle formation (NPF) events were found to be more frequent in spring than in autumn. The mean duration, growth rates and maximum diameters had ranges of 5.3–13.2 h, 2.4–4.0 nm h−1 and 35–47 nm, respectively. In addition, one shrinkage event occurred and had a duration of 2.2 h and a shrinkage rate of −2.5 nm h−1. During a period of atmospheric stagnation conditions under the influence of mountain breezes, three consecutive NPF events occurred. The high frequency of the NPF events was attributed to higher temperature and radiation levels and lower relative humidity than during a previous day with similar stagnant conditions but no nucleation occurrence. According to correlation analysis, mineral components correlated with particle number in the Aitken mode, while metals and secondary inorganic aerosols correlated with particle number in the finer and larger fractions, respectively. Pollutants such as CO, NO2, NO and black carbon showed moderate and high correlations with particle number in the submicron fraction. To assess the impact of the particle number contribution according to sources, a new approach was introduced using black carbon concentrations, resulting in four major contributors: urban background, traffic, NPF and biomass burning. The proposed approach was validated by means of different models based on the aerosol spectral dependencies and chemical compositions that classify aerosol populations. Both the models and the proposed approach identified biomass burning and fossil fuel particles during the same periods, and the results showed good agreement. The proposed approach can guide future studies attempting to account for submicron particle contributions in other urban environments.