GREGORI DE ARRUDA MOREIRA

GREGORI DE ARRUDA MOREIRA

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Comparing lidar and ceilometer backscattering measurements for the detection of aerosol layers in the PBL over São Paulo, Brazil
2021 - SANTOS, AMANDA V.; LANDULFO, EDUARDO; MOREIRA, GREGORI A.; MARQUES, MARCIA T.A.; ANDRADE, MARIA F.
The Planetary Boundary Layer (PBL) is the lowest part of the troposphere and it is directly influenced by the Earth’s surface and anthropogenic activities. The concentration of aerosol in the PBL is typically much higher than in the free troposphere. Given that most of the air pollution in the troposphere is capped by this layer, obtaining the PBL height (PBLH) and its evolution during the day can assist in monitoring and studying aerosol concentrations and properties and its impact on air quality. Multi-instrument monitoring of the PBLH can assist in identifying the arrival of different air masses and tracking the evolution of aerosol layers during the day. Due to their lower cost, ceilometers can be powerful tools to enhance these measurements, although such an instrument has a few limitations when compared to lidars. The weaker laser light source used in ceilometers can limit the detection of aerosol layers to a few kilometers in height, depending on the presence and distribution of clouds and aerosols in the atmosphere. Given that some methods to estimate the PBLH need strong gradients in the concentration of aerosols to identify it correctly, the improper identification of the aerosol layers can become problematic for obtaining the PBLH. We compared lidar and ceilometer data from two instruments located in the city of São Paulo, Brazil, approximately 15 km from each other. We found that, in clear sky conditions, it is possible to correctly identify aerosol layers in the PBL with data from both instruments. The presence of clouds, signal attenuation and noise can sometimes cause errors in the identification of aerosol layers, especially when using ceilometer data. We found that, despite not being co-located, both instruments show similar profiles, up to a few kilometers in height.
Performance assessment of aerosol-lidar remote sensing skills to retrieve the time evolution of the urban boundary layer height in the Metropolitan Region of São Paulo City, Brazil
2022 - MOREIRA, GREGORI de A.; OLIVEIRA, AMAURI P. de; SANCHEZ, MACIEL P.; CODATO, GEORGIA; LOPES, FABIO J. da S.; LANDULFO, EDUARDO; MARQUES FILHO, EDSON P.
This paper investigates the performance of seven methods of retrieving the planetary boundary layer height (PBLH) from lidar measurements carried out in the Metropolitan Region of S˜ao Paulo (MRSP) during two MCITY-BRAZIL field campaigns of 2013. The performance is objectively assessed considering as reference the PBLH retrieved from rawinsonde carried out every 3 h during these campaigns. The role of clouds and aerosol load in the performance of the seven methods is analysed considering three case study scenarios representative of typical atmospheric conditions in the MRSP: (a) winter clean atmosphere, (b) summer low clouds and aerosol multilayers, (c) summer sea-breeze intrusion. Corroborating the case study results, the objective analysis indicated that most of the lidar methods retrieved PBLH closer to the top of the entrainment zone than the mixed layer, contradicting their definition. During daytime, the Wavelet Covariance Transform Method performs better than all the other six methods. The Inflexion Point Method performed better to estimate the Residual Layer height during night-time. In average, the diurnal evolution of the PBLH and its local rate of change based on lidar and rawinsonde measurements are in agreement.
Aerosol number fluxes and concentrations over a southern European urban area
2022 - CASQUERO-VERA, J.A.; LYAMANI, H.; TITOS, G.; MOREIRA, G. de A.; BENAVENT-OLTRA, J.A.; CONTE, M.; CONTINI, D.; JARVI, L.; OLMO-REYES, F.J.; ALADOS-ARBOLEDAS, L.
Although cities are an important source of aerosol particles, aerosol number flux measurements over urban areas are scarce. These measurements are however important as they can allow us to identify the different sources/sinks of aerosol particles and quantify their emission contributions. Therefore, they can help us to understand the aerosol impacts on human health and climate, and to design effective mitigation strategies through the reduction of urban aerosol emissions. In this work we analyze the aerosol number concentrations and fluxes for particles with diameters larger than 2.5 nm measured by eddy covariance technique at an urban area (Granada city, Spain) from November 2016 to April 2018. This is the first study of particle number flux in an urban area in the Iberian Peninsula and is one of the few current studies that report long-term aerosol number flux measurements. The results suggest that, on average, Granada urban area acted as a net source for atmospheric aerosol particles with median particle number flux of 150 × 106 m−2 s−1. Downward negative fluxes were observed in only 12% of the analyzed data, and most of them were observed during high aerosol load conditions. Both aerosol number fluxes and concentrations were maximum in winter and 50% larger than those measured in summer due to the increased emissions from domestic heating, burning of residual agricultural waste in the agricultural area surrounding the site, as well as to the lower aerosol dilution effects during winter. The analysis of the seasonal diurnal variability of the aerosol number concentration revealed the significant impact of traffic emissions on aerosol population over Granada urban area in all seasons. It also shows the impact of domestic heating and agricultural waste burning emissions in winter as well as the influence of new particle formation processes in summer and spring seasons. Closer analysis by wind sector demonstrated that both aerosol concentrations and fluxes from urban sector (where high density of anthropogenic sources is located) were lower than those from rural sector (which includes agricultural area but also the main highway of the city). This evidences the strong impact of aerosol emissions from traffic circulating on the highway on aerosol population over our measurement site.
Lidar observations in South America
2021 - LANDULFO, EDUARDO; CACHEFFO, ALEXANDRE; YOSHIDA, ALEXANDRE C.; GOMES, ANTONIO A.; LOPES, FABIO J. da S.; MOREIRA, GREGORI de A.; SILVA, JONATAN J. da; ANDRIOLI, VANIA; PIMENTA, ALEXANDRE; WANG, CHI; XU, JIYAO; MARTINS, MARIA P.P.; BATISTA, PAULO; BARBOSA, HENRIQUE de M.J.; GOUVEIA, DIEGO A.; GONZALEZ, BORIS B.; ZAMORANO, FELIX; QUEL, EDUARDO; PEREIRA, CLODOMYRA; WOLFRAM, ELIAN; CASASOLA, FACUNDO I.; ORTE, FACUNDO; SALVADOR, JACOBO O.; PALLOTTA, JUAN V.; OTERO, LIDIA A.; PRIETO, MARIA; RISTORI, PABLO R.; BRUSCA, SILVINA; ESTUPINAN, JOHN H.R.; BARRERA, ESTIVEN S.; ANTUNA-MARRERO, JUAN C.; FORNO, RICARDO; ANDRADE, MARCOS; HOELZEMANN, JUDITH J.; GUEDES, ANDERSON G.; SOUSA, CRISTINA T.; OLIVEIRA, DANIEL C.F. dos S.; DUARTE, EDICLE de S.F.; SILVA, MARCOS P.A. da; SANTOS, RENATA S. da S.
In Part II of this chapter, we intend to show the significant advances and results concerning aerosols’ tropospheric monitoring in South America. The tropospheric lidar monitoring is also supported by the Latin American Lidar Network (LALINET). It is concerned about aerosols originating from urban pollution, biomass burning, desert dust, sea spray, and other primary sources. Cloud studies and their impact on radiative transfer using tropospheric lidar measurements are also presented.
Validation of AEOLUS L2A products using a multiwavelength lidar system at SPU Lidar Station - Brazil
2020 - LOPES, FABIO; YOSHIDA, ALEXANDRE; CACHEFFO, ALEXANDRE; SILVA, JONATAN; MOREIRA, GREGORI; LANDULFO, EDUARDO
Exploring the twilight zone
2020 - SILVA, JONATAN da; MORAIS, FERNANDO G.; FRANCO, MARCO A.; LOPES, FABIO J.S.; ARRUDA, GREGORI de A.; YOSHIDA, ALEXANDRE C.; CORREIA, ALEXANDRE; LANDULFO, EDUARDO
This study shows a set of analysis of measurements from ground-based and satellite instruments to characterize the twilight zone (TLZ) between clouds and aerosols in São Paulo, Brazil. In the vicinity of clouds turbulence measurements showed an intense upward movement of aerosol layers, while sunphotometer results showed an increase in aerosol optical depth, and lidar measurements showed an increase in the backscatter vertical profile signal.
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.
Analyzing the turbulent planetary boundary layer by remote sensing systems
2019 - MOREIRA, GREGORI de A.; GUERRERO-RASCADO, JUAN L.; BENAVENT-OLTRA, JOSE A.; ORTIZ-AMEZCUA, PABLO; ROMAN, ROBERTO; BEDOYA-VELASQUEZ, ANDRES E.; BRAVO-ARANDA, JUAN A.; REYES, FRANCISCO J.O.; LANDULFO, EDUARDO; ALADOS-ARBOLEDAS, LUCAS
The planetary boundary layer (PBL) is the lowermost region of troposphere and is endowed with turbulent characteristics, which can have mechanical and/or thermodynamic origins. This behavior gives this layer great importance, mainly in studies about pollutant dispersion and weather forecasting. However, the instruments usually applied in studies of turbulence in the PBL have limitations in spatial resolution (anemometer towers) or temporal resolution (instrumentation aboard an aircraft). Ground-based remote sensing, both active and passive, offers an alternative for studying the PBL. In this study we show the capabilities of combining different remote sensing systems (microwave radiometer – MWR, Doppler lidar – DL – and elastic lidar – EL) for retrieving a detailed picture on the PBL turbulent features. The statistical moments of the high frequency distributions of the vertical wind velocity, derived from DL, and of the backscattered coefficient, derived from EL, are corrected by two methodologies, namely first lag correction and 􀀀2=3 law correction. The corrected profiles, obtained from DL data, present small differences when compared with the uncorrected profiles, showing the low influence of noise and the viability of the proposed methodology. Concerning EL, in addition to analyzing the influence of noise, we explore the use of different wavelengths that usually include EL systems operated in extended networks, like the European Aerosol Research Lidar Network (EARLINET), Latin American Lidar Network (LALINET), NASA Micro-Pulse Lidar Network (MPLNET) or Skyradiometer Network (SKYNET). In this way we want to show the feasibility of extending the capability of existing monitoring networks without strong investments or changes in their measurements protocols. Two case studies were analyzed in detail, one corresponding to a well-defined PBL and another corresponding to a situation with presence of a Saharan dust lofted aerosol layer and clouds. In both cases we discuss results provided by the different instruments showing their complementarity and the precautions to be applied in the data interpretation. Our study shows that the use of EL at 532 nm requires a careful correction of the signal using the first lag time correction in order to get reliable turbulence information on the PBL.
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.