Browsing by Author "Fialho, Paulo"
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- 7Be as a tracer on the investigation of upper tropospheric dispersion of Saharan dust during the mid-winter 2000 storm events (Azores).Publication . Rodrigues, A. F.; Holmes, Charles; Pio, Casimiro; Marot, Marci; Fialho, Paulo7Be is a nuclide that acts like a tracer of input from the stratosphere and upper troposphere, where it is produced by spallation processes of light atmospheric nuclei such as nitrogen 14, oxygen 16 and carbon 12, with protons and neutrons (Zanis et al. 2000). By measuring the activity of beryllium isotopes attached to submicrometer aerosol particles, information on the mechanisms of exchange between the stratosphere and troposphere is obtained. […].
- Absorption coefficients by aerosols in remote areas: a new approach to decouple dust and black carbon absorption coefficient using seven-wavelength Aethalometer dataPublication . Fialho, Paulo; Hansen, Anthony; Honrath, RichardWe present a new approach to decouple aerosol absorption coefficients due to iron oxide in Sahara dust from those due to black carbon (BC) particles. Absorption coefficients, σaerosol(λ,t), were measured at the summit of Pico mountain (2225 m ASL) in the Azores Islands using a seven-wavelength Aethalometer. Measurements between 27th July and 1st August, 2001, are analyzed here. Variations in aerosol absorption coefficients were uncorrelated to those of CO during the latter part of this period, suggesting the presence of non-combustion-derived aerosol, apparently African dust. To differentiate between BC and other absorbing particles, we analyzed the wavelength dependence of σaerosol(λ,t) and determined a best-fit exponent during the later period equal to -2.9±0.2, somewhat lower than previously reported for soil dust. Using this method, it is possible to estimate the aerosol absorption due to BC and that due to soil dust separately through the full period analyzed.
- Aerosol chemical elemental mass concentration at lower free tropospherePublication . Freitas, Maria do Carmo; Dionísio, Isabel; Fialho, Paulo; Barata, FilipeThis paper shows the use of Instrumental neutron activation analysis (INAA) technique to determine elemental masses collected by a seven-wavelength Aethalometer instrument at the summit of Pico mountain in the Azorean archipelago, situated in the Central North Atlantic Ocean. Each sample corresponds to air particulate matter measured continuously for periods of approximately 24 h taken from 14th July 2001 through 14th July 2002. The statistical analysis of the coefficients of correlation between all the elements identified, permitted to establish six groups that could potentially be associated with the type of source responsible for the aerosol sampled in the lower free troposphere at the Azorean archipelago. Calculation of the synoptic back trajectories helped to corroborate the use of the iron/cesium relation as a tracer for the Saharan dust aerosol. It was demonstrated that INAA constituted an important tool to identify these events.
- Aerosol Measurements in the Free Troposphere at the North Atlantic Pico Mountain Observatory in the Azores.Publication . Mazzoleni, Claudio; Fialho, Paulo; Gorkowski, Kyle; Owen, Robert; Dziobak, Michael P.; Hueber, Jacques; Dzepina, Katja; Kramer, Louisa; Olsen, Seth C.; Kumar, Sumit; Helmig, DetlevPico is a small island (447 km2) in the archipelago of the Azores, Portugal, in the North Atlantic Ocean. The island has a very steep inactive volcano. An atmospheric monitoring station (Pico Mountain Observatory) was established close to the summit of the volcano by the late Dr. Richard Honrath and colleagues in 2001. The station, far from persistent local sources, is located near the northern cliff of the summit caldera at an altitude of 2225 meters. The station altitude is typically well above the boundary layer during summertime, when average marine boundary-layer heights are below 1200 meters and rarely exceed 1300 meters. Air masses reaching the station are often transported from North America and seldom from Europe or North Africa. The station’s uniqueness and significance lie in its location that allows study of the transport and evolution of gases and aerosols from North America in the free troposphere. Until recently, the focus was on the measurement and analysis of trace gases (ozone, carbon monoxide, non-methane hydrocarbons, nitrogen oxides) and light-absorbing aerosol (black carbon and iron oxide). Aerosol light attenuation has been measured at the site since 2001 using a seven-wavelengths aethalometer. An optical particle sizer was installed at the site in 2010 and has been running in parallel to the aethalometer for two seasons. A three-wavelength nephelometer, to measure the aerosol total- and back-scattering, and aerosol samplers for morphological and chemical analysis will be installed at the site in 2012. Our goal is to enhance the observatory monitoring capabilities for aerosol research. The objectives of this new research program are to: (a) assess background as well as specific event tropospheric aerosol properties, (b) compare aerosol and gases measurements with model outputs, and (c) use the data collected to provide satellite validation. This research is anticipated to enhance our understanding of the interactions between tropospheric aerosols, clouds, and climate by allowing, for example, the analysis of North American outflows and seasonal changes, the assessment of different source regions, the estimation of aerosol radiative forcing above marine clouds and in clear sky, and the study of the relative contribution of anthropogenic versus biomass burning emissions. In this poster we present a preliminary analysis of the black carbon and aerosol size data in conjunction with retroplume model analysis.
- Aerosol Optical Depth measurements in the Azores.Publication . Carvalho, Fernanda; Henriques, Diamantino; Fialho, PauloA preliminary analysis of AOD results from sun-photometer measurements collected at Jose Agostinho Observatory at Angra do Heroísmo (Terceira Island, the Azores) was presented. The observational period ranges from August 2004 to December 2007, using a SP02 sun-photometer at wavelengths 412, 500, 675, and 862 nm, coupled to a 2AXP sun-tracker. The sampling interval is 5 s and data is filtered for cloud contamination in a time window of 10 minutes. Most AOD 500 nm values are below 0.3, showing a small variation during the day; frequency distribution shows a typical right skew distribution. Alpha and beta Angstrom coefficients were also computed and analyzed in the same way. Alpha values are generally positive and lower than 4, while beta values are below 1.5. AOD results from the AERONET station at Horta Observatory (Faial Island, the Azores) were also used and compared with Angra data. AOD and Angstrom coefficients were also analyzed with wind results from the automatic weather station located at both observatories. Results show different wind distributions due to different exposures; however, systematic higher AOD values are found at Horta. The proximity of the two sites indicates that these differences are more likely due to different instruments and processing methods used.
- Aerosol optical properties at Santiago Island, Cape Verde.Publication . Cerqueira, Mário; Pio, Casimiro; Fialho, Paulo; Cardoso, João; Nunes, Teresa; Almeida, S. M.> huge amounts of mineral dust are emitted every year from the Sahara desert to the atmosphere; > optical parameters of mineral aerosols determine the direct interaction of solar and terrestrial radiation in the atmosphere through scattering and absorption; > mineral dust has a great impact on cloud formation leading to additional indirect radiation effects; > The dense haze from dust events is also known to affect visibility.
- Alterações Climáticas : O valor estratégico dos AçoresPublication . Fialho, PauloA crescente preocupação com as alterações climáticas tem levado à expansão da rede de monitorização da atmosfera (GAW) na sua vertente química e física. Esta rede tem na sua base as diversas plataformas terrestres de observação da atmosfera que se encontram associadas aos Serviços Nacionais de Meteorologia e de Hidrologia (SNMH) dos diversos países envolvidos no programa. A Organização Mundial de Meteorologia (OMM) pediu aos seus membros (os SMH) que fossem tidas em consideração as medidas da composição química da atmosfera encorajando-os a integrarem nas suas atividades a observação da composição química da atmosfera. […].
- Amostragem de partículas em suspensão na atmosfera do Atlântico Norte.Publication . Rodrigues, A. F.; Fialho, Paulo; Pio, CasimiroOs aerossóis têm géneses e composições muito diferenciadas. Estes têm origem nas emissões naturais (por exemplo o spray marinho e as emissões vulcânicas) ou antropogénicas (por exemplo os processos de combustão). A caracterização física e química dos aerossóis é importante para compreender a relação entre: a sua origem; os mecanismos de transporte difusivo das massas de ar atmosférico; os processos de nucleação associados à formação de nuvens; e os mecanismos de transformação química. O Arquipélago dos Açores localizado numa zona remota (longe das emissões poluentes do continente Europeu e Americano e com emissões locais desprezáveis), é o local ideal para a caracterização física e química das massas de ar que o atravessam. A sua atmosfera "limpa" permite o estudo do transporte a longas distâncias de poluentes entre os continentes americano e europeu. Neste contexto efectuou-se a caracterização física do aerossol, recorrendo a um colector de partículas de grande volume (High-Volume - figura 1) com uma cabeça de pré-selecção de 10 μm. Os aerossóis foram separados em duas fracções, uma fina (diâmetros inferiores a 10 μm) essencialmente associada a contribuições antropogénicas, e outra grosseira (diâmetros entre 0,95 μm e 10 μm) maioritariamente relacionada com contribuições naturais. A massa de aerossol amostrada é determinada pela pesagem dos filtros onde este é recolhido, conjuntamente são efectuadas medidas de caudal volúmico e tempo de amostragem.
- Analysis and results of the absorption photometer workshop.Publication . Henzing, Bas; Fialho, Paulo; Mocnik, Grisa; Leeuw, Gerrit; Wiedensohler, Alfred; Müller, Thomas
- Analysis of Atmospheric Aerosols Using the Lisbon Nuclear MicroporePublication . Rita, E. M.; Alves, L. C.; Reis, M. A.; Rodrigues, A. F.; Fialho, Paulo; Soares, J. C.The nuclear microprobe installed at Instituto Tecnológico e Nuclear, in Lisbon, was used in the analysis of aerosols collected at the Azores islands. Samples from two different aerosol groups were analysed. One referred to aerosols that were carried from North America and the other one contained aerosols that were carried from the Sahara desert and crossed over Europe. Coarse and fine fractions were analysed for each aerosol group and two-dimensional elemental maps were constructed, which allowed the identification of several individual particles. For particles of interest, elemental spatial correlations and dimensions were determined and point analysis was also carried out (depth information was achieved by fitting Rutherford backscattering spectra). Some of these particles are quite interesting. For instance, in the fine fraction of the aerosols that were carried from North America, particles were found with Cu and Cl in the atomic proportion 1:2 and with dimensions 15 x 15 x 15 μm³, and in the corresponding coarse fraction a particle with K and S was identified, with dimensions 28 x 35 x 30 μm³. Some differences were found between the aerosols groups. One example of these are Ti particles (fine fraction) and Rb (coarse fraction) that were identified in one group (Sahara desert and Europe), but not in the other.