Walter Nakaema - Academia.edu (original) (raw)

Papers by Walter Nakaema

Atmosphere, 2018

In this study, an air mass (containing a cirrus cloud) was detected by light detection and rangin... more In this study, an air mass (containing a cirrus cloud) was detected by light detection and ranging (lidar) above São Paulo (Brazil) in June 2007 and tracked around the globe, thanks to Lagrangian calculations as well as ground-based and satellite observations. Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) data were also used to provide locations of occurrence of cirrus around the globe and extract their respective macro physical parameters (altitude and temperature). An analysis of the air mass history based on Lagrangian trajectories reveals that water coming from the Equator is channelized through the southern subtropical jet for weeks. In this case, the back-trajectories showed that the cirrus cloud detected at São Paulo was a mixture of air masses from two different locations: (1) the active convective area located around the Equator, with transport into the upper troposphere that promotes cirrus cloud formation; and (2) the South Pacific Ocean, wit...

Proceedings of the 16th International Congress of the Brazilian Geophysical Society&Expogef, 2019

Contents of this paper were reviewed by the Technical Committee of the 16 th International Congre... more Contents of this paper were reviewed by the Technical Committee of the 16 th International Congress of the Brazilian Geophysical Society and do not necessarily represent any position of the SBGf, its officers or members. Electronic reproduction or storage of any part of this paper for commercial purposes without the written consent of the Brazilian Geophysical Society is prohibited.

Energy Procedia, 2017

After the Ressacada Project experience acquired from 2011 to 2015 when PUCRS, UNESP and other ins... more After the Ressacada Project experience acquired from 2011 to 2015 when PUCRS, UNESP and other institutions conducted three controlled CO 2 release experiments, PETROBRAS, the national oil company that is sponsoring the project, has launched a new challenge to its partners. The company stimulated the implementation of a new Brazilian experimental site where there will be a deepening of studies in geologically more complex conditions and more challenging from a technological point of view. The choice of an area inside PUCRS campus, in Viamão-Rio Grande do Sul state, was motivated by a predominantly clay subsoil and the privileged location of the site in terms of ease logistics and security, which is required for a project of this size that houses high-tech equipment with significant cost. The CO 2 MOVE project started at 2015 with the subsurface characterization of the site and the assembly and manufacture of an automated system for CO 2 and gas tracers with injection capacity for 5 to 50 kg/day. Based on physical characterization studies and on numerical modeling that is being developed, the site infrastructure will be completed in the next months with the positioning of vertical injection wells, monitoring wells, and other equipment and monitoring mesh. Monitoring tools should be arranged in an area of approximately 100m 2 , occupying the entire region surrounding the injection wells. Fieldwork involving CO 2 injection and monitoring should have a 60 days duration of which 15 days are for preliminary surveys (pre-injection), 30 days for injection and CO 2 monitoring and the last 15 days for post-injection measurements. Following this work, the collected data will be analyzed in the university labs.

In this work, we present a variation of the technique CRDS (Cavity Ring-Down Spectroscopy) to obt... more In this work, we present a variation of the technique CRDS (Cavity Ring-Down Spectroscopy) to obtain simultaneously a multicomponent absorption spectrum in a broad visible range. This new approach uses the Supercontinuum (SC) spectrum (resulting from irradiation of nonlinear media by femtosecond lasers, or simply generated by compact sources) as a light source to illuminate the cavity. In this context it is described the features of the modules assembling a MC-SC-CRDS (Multicomponent Supercontinuum Cavity Ring-Down Spectroscopy): a set of high refletivity mirrors, the resonant cavity and the detection system. Some problems related to the multimode excitation, stray light, effective use of the dynamic range of the detector, the poor resolution of the instrument to resolve narrow absorption lines are issued. We present the absorption spectra of H 2 O (polyads 4ν, 4ν + δ) and O 2 (spin-forbidden b-X branch) measured simultaneously by this technique in the visible range and a comparison with the absorption lines based on HITRAN database is made to demonstrate the functionality of this method.

Optica Pura y Aplicada

We compare the performance of some available atmospheric models for the atmosphere of Sao Paulo (... more We compare the performance of some available atmospheric models for the atmosphere of Sao Paulo (Brazil) to be used in case of absence of radio-sounding data for the given day. We developed our own model (SPm) from historic radio-sounding data in order to create a local model. By performing inversions of lidar signals (distributed over a year), we could benchmark the performance of the models against radio-sounding data. SPm and ISA-15N show the smallest deviation and represent, therefore, the best fallback models for this southern latitude.

Lidar Technologies, Techniques, and Measurements for Atmospheric Remote Sensing X, 2014

Currently one of the main challenges in CO2 storage research is to grant the development, testing... more Currently one of the main challenges in CO2 storage research is to grant the development, testing and validation of accurate and efficient Measuring, Monitoring and Verification (MMV) techniques to be deployed at the final storage site, targeting maximum storage efficiency at the minimal leakage risk levels. For such task a mimetic sequestration site has been deployed in Florianopolis, Brazil, in order to verify the performance of monitoring plataforms to detect and quantify leakages of ground injected CO2, namely a Cavity Ring Down System (CRDS) - Los Gatos Research - an Eddy Covariance System (Campbell Scientific and Irgason) and meteorological tower for wind, humidity, precipitation and temperature monitoring onsite. The measurement strategy for detecting CO2 leakages can be very challenging since environmental and phytogenic influence can be very severe and play a role on determining if the values measured are unambiguous or not. One external factor to be considered is the amount of incoming solar radiation which will be the driving force for the whole experimental setup and following this reasoning the amount of aerosols in the atmospheric column can be a determinant factor influencing the experimental results. Thus the investigation of measured fluxes CO2 and its concentration with the aforementioned experimental instruments and their correlation with the aerosol data should be taken into account by means of satellite borne systems dedicated to measure aerosol vertical distribution and its optical properties, in this study we have selected CALIPSO and MODIS instrumentation to help on deriving the aerosol properties and CO2 measurements.

Lidar Technologies, Techniques, and Measurements for Atmospheric Remote Sensing X, 2014

The Latin American Lidar Network (LALINET) is the aerosol lidar network operating over South Amer... more The Latin American Lidar Network (LALINET) is the aerosol lidar network operating over South America. LALINET is now an operative network performing a schedule of routine measurements and, currently, is composed by 9 stations distributed over South America. The main objective of LALINET is to generate a consistent and statistically relevant database to enhance the understanding of the particle distribution over the continent and its direct and indirect influence on climate. The creation of an un-biased spatiotemporal database requires a throughout review of the network on two pillars: instrumentation and data processing. Because most of the LALINET systems are not series-produced instruments and, therefore, present large differences in configuration and capabilities, attempts for network harmonization and, consequently, optimization are mandatory. In this study a review of the current instrumental status of all LALINET systems is done and analyzed in detail in order to assess the potential performance of the network and to detect networking weaknesses.

Energy Procedia, 2014

Currently one of the main challenges in CO 2 storage research is the development, testing and val... more Currently one of the main challenges in CO 2 storage research is the development, testing and validation of accurate and efficient Measuring, Monitoring and Verification (MMV) techniques to be deployed at geological sequestration sites that are cost effective yet help minimize risk. This perspective motivated PETROBRAS, the National Oil Major in Brazil, through its R&D investments portfolio to prioritize research projects that would contribute to decreasing the technological gap in the area. The Company's periodic surveys indicated the lack of infrastructure, as well as expertise in CO 2 MMV, as two of the most critical issues at the national level. In order to bridge that gap, initial steps were taken in 2010 for the start-up and development of the first CO 2 MMV Field Lab in Brazil, fully sponsored by PETROBRAS, with a long term goal of enabling the ranking of the best, most costeffective MMV technology alternatives to be deployed at commercial large scale CCGS sites scheduled to be installed in the country. In addition to providing basic infrastructure to carry out the CO 2 injection and controlled release experiments, the facility was designed for the simultaneous testing of multiple measuring methodologies. Additional benefits of the initiative are the creation of expertise and the acceleration of the know-how in MMV in Brazil, as well as the development of a deeper and more

Brazilian Journal of Physics, 1999

We h a ve observed changes in the morphology of InP lms grown in epi-ready substrates and on patt... more We h a ve observed changes in the morphology of InP lms grown in epi-ready substrates and on patterns created by photo and plow-mode AFM lithography. These changes are attributed to di erent levels of contamination of the surface, which f a vor nucleation of clusters over a two-dimensional lm for the lithography-processed surface. The area of nucleation is smaller than the dimensions of the patterns created by lithography, so no size e ects due to the presence of the pattern could be observed. The lm morphologies exhibited well de ned exponents for system sizes smaller than 0.2 m but no de ned growth exponent.

Sensors, 2011

A multiwavelength, multicomponent CRDS gas sensor operating on the basis of a compact photonic cr... more A multiwavelength, multicomponent CRDS gas sensor operating on the basis of a compact photonic crystal fibre supercontinuum light source has been constructed. It features a simple design encompassing one radiation source, one cavity and one detection unit (a spectrograph with a fitted ICCD camera) that are common for all wavelengths. Multicomponent detection capability of the device is demonstrated by simultaneous measurements of the absorption spectra of molecular oxygen (spin-forbidden b-X branch) and water vapor (polyads 4v, 4v + δ) in ambient atmospheric air. Issues related to multimodal cavity excitation, as well as to obtaining the best signal-to-noise ratio are discussed together with methods for their practical resolution based on operating the cavity in a "quasi continuum" mode and setting long camera gate widths, respectively. A comprehensive review of multiwavelength CRDS techniques is also given.

Cirrus clouds with several important and climate-related applications are product of weather proc... more Cirrus clouds with several important and climate-related applications are product of weather processes, and hence their occurrence and macrophysical/optical properties can vary significantly over different regions of the world. In this sense, a few case studies of cirrus clouds observed at both subtropical and polar latitudes are examined. Observations are carried out in three stations: Sao Paulo (Brazil, 23.6°S/46.8°W) and Sta. Cruz de Tenerife (Spain, 28.5°N/16.3°W), being both subtropical sites, and the Belgrano II base (Argentina, 78ºS/35ºW) in the Antarctic continent. Active remote sensing (LIDAR) is used for profiling measurements, and cirrus clouds features are retrieved by using a recently proposed methodology. Local radiosounding profiles are also used for cirrus-temperature correlation analysis. Optical and macrophysical properties (COD-cloud optical depth, top/base heights and Lidar Ratio, mainly) of both the subtropical and polar cirrus clouds are reported. This study is...

Understanding the impact of cirrus cloud on modifying both the solar reflected and terrestrial em... more Understanding the impact of cirrus cloud on modifying both the solar reflected and terrestrial emitted radiations is crucial for climate studies. Unlike most boundary layer stratus and stratocumulus clouds that have a net cooling effect on the climate, high-level thin cirrus clouds have a warming effect on our climate. However, the satellites as GOES from the NOAA series are limited to the cloud top and its reflectivity or brightness temperature, without assessing accurately the optical depth or physical thickness. Other more recent sensors as MODIS are able to determine optical depths for aerosols and clouds but when related to cirrus they are still inaccurate. Research programs as First ISCCP, FIRE, HOIST, ECLIPS and ARM have concentrated efforts in the research of cirrus, being based mainly on the observations of combined terrestrial remote sensing and airplanes instruments. LIDARs are able to detect sub-visual cirrus cloud (SVCs) in altitudes above 15 km and estimate exactly the...

ABSTRACT A high sensitive Cavity Ring-Down Spectroscopy (CRDS) system is proposed to monitoring t... more ABSTRACT A high sensitive Cavity Ring-Down Spectroscopy (CRDS) system is proposed to monitoring the aerosol extinction coefficient in the city of São Paulo, Brazil. A continuous range of wavelengths varying from 645 and 675 nm is used to excite the cavity. This continuous range is provided from a fiber-based super continuum light source illuminating one end of the cavity at a repetition rate of 25 kHz. The signal through the cavity is selected by a spectrometer and then recorded by an iCCD camera. The reference measurement is performed under vacuum while the measurement for absorption/extinction is performed by sampling ambient air (preferably from an atmosphere containing aerosol particles) directly into the cavity. The first measurement performed with a volume of air with a relative humidity of around 54% and temperature of 295 K showed strong absorption peaks respectively at 647.7, 651.5 and 654.9 nm due to the presence of relatively high concentration of water vapor in the sampled air. In spectral windows that are free from molecular resonances of H2O (in our case 665−675 nm) the wavelength averaged rate of the energy loss determined in this way is 5.7 ± 0.3 E−8 per cm. The Rayleigh scattering theory yields a similar value of 5.3 E−8 per cm and the small discrepancy of about 4 E−9 per cm is likely caused by Mie scattering on residual dust particles. The resulting experimental spectra can be compared with results obtained by the Mie theory to estimate the respective size distribution of particles.

ABSTRACT The extinction-to-backscatter ratio (also called lidar ratio-LR) is an important paramet... more ABSTRACT The extinction-to-backscatter ratio (also called lidar ratio-LR) is an important parameter which provides information on the transmission and reflection properties of cirrus clouds and also on the ice crystal properties due to their dependence on the particle shape, size and orientation for the particles. In this study is showed an innovative method to obtain theLR for each cloud layer through iterative processes, applying a numerical routine developed at the Center for Lasers and Applications (CLA/IPEN-Brazil) in cooperation with the Laboratoire Amosphères, Milieus, Observations Spatiales, Institut Pierre Simon Laplace/Versailles-Saint Quentin University (LATMOS/IPSL-France). The resulting LR values were obtained based on measurements of the MSP (Metropolitan City of São Paulo) - lidar system, performed on 11th June 2007, comprehending 298 minutes separated in 7 distinct so called stationary periods. For the first four periods, was observed two distinct layers of clouds with LR values varying between 28±15 and 35 ± 18 sr for the first layer and 37±11srand 74±14 sr for the second, indicating the presence of both small and large ice crystals composed by solid and hollow columns in majority. The last 3 periods of measurements in turn presented a mono¬layer cloud with LR about 19±04 sr, what corresponds to a relatively small solid needles, plates and column crystals.

Atmospheric Measurement Techniques Discussions, 2013

This paper presents a methodology to calculate lidar ratios for distinct cirrus clouds that has b... more This paper presents a methodology to calculate lidar ratios for distinct cirrus clouds that has been developed and implemented for a site located in the Southern Hemisphere. The cirrus cloud lidar data processing aims to consider a large cloud variability and cirrus cloud monitoring through a robust retrieval process. Among cirrus features estimates for complex scenes that lidar systems can provide, we highlight cloud geometrical information and extinctionto-backscatter ratio (known as lidar ratio or LR). In general, direct information on cirrus cloud microphysics is difficult to derive because LR depends on the presence of ice crystals and their properties such as shape, size, composition and orientation of particles. An iterative process to derive a stable LR value has been proposed. One of the keys is to restrict the analysis to conditions allowing accurate multilayer events. This method uses nonparametric statistical approaches to identify stationary periods according to cloud features and variability. Measurements performed in the region of the metropolitan city of São Paulo (MSP) have been used to implement and test the methodology developed for cirrus cloud characterization. Good results are represented by examining specific cases with multilayer cirrus cloud occurrence. In addition to the geometrical parameters obtained, cirrus LR values were calculated for a single day ranging from 19 ± 01 sr to 74 ± 13 sr for 2 observed layers. This large difference in LR can indicate a mixture of ice crystal particles with different sizes and shapes in both layers of the cirrus clouds. Trajectory analyses indicate that both of these cloud layers can be associated with different air mass and should be considered as 2 distinct clouds in climatology. www.atmos-meas-tech.net/6/3197/2013/

Optica Pura y Aplicada, 2014

Nature Communications, 2011

Because of the potential impact on agriculture and other key human activities, efforts have been ... more Because of the potential impact on agriculture and other key human activities, efforts have been dedicated to the local control of precipitation. The most common approach consists of dispersing small particles of dry ice, silver iodide, or other salts in the atmosphere. Here we show, using field experiments conducted under various atmospheric conditions, that laser filaments can induce water condensation and fast droplet growth up to several µm in diameter in the atmosphere as soon as the relative humidity exceeds 70%. We propose that this effect relies mainly on photochemical formation of p.p.m.-range concentrations of hygroscopic Hno 3 , allowing efficient binary Hno 3 -H 2 o condensation in the laser filaments. Thermodynamic, as well as kinetic, numerical modelling based on this scenario semiquantitatively reproduces the experimental results, suggesting that particle stabilization by Hno 3 has a substantial role in the laser-induced condensation. close to Geneva (46°12' North, 6°5' East, 380 m above sea level). This location was chosen to get the benefit from the relatively warm water flow from the Lake of Geneva acting as a heat buffer, locally increasing the RH. As detailed in , data were acquired in a wide variety of atmospheric conditions: RH from 35 to 100%, temperature between 2 and 36 °C. Furthermore, experiments at all times of the day and the night ensured that both phases of increase and decrease of temperature and RH have been recorded.

Journal of the Air & Waste Management Association, 2010

Particulate black or elemental carbon (EC) (black carbon [BC]) and organic carbon (OC) affect cli... more Particulate black or elemental carbon (EC) (black carbon [BC]) and organic carbon (OC) affect climate, visibility, and human health. Several "top-down" and "bottom-up" global emission inventories for these components have compiled country-wide emission factors, source profiles, and activity levels that do not necessarily reflect local conditions. Recent estimates of global BC and OC emissions range from 8 to 24 and 33 to 62 Tg (10 12 g) per year, respectively. U.S. BC emissions account for 5.6% of the global total emissions. Uncertainties in global BC emission estimates are a factor of 2 or more. The U.S. National Emissions Inventory is well documented, but its major source categories are not easily related to EC-and OCemitting source subcategories. California's bottom-up emission inventory is easily accessible at many levels of detail and provides an example of how sources can be regrouped for speciated emission rates. PM 2.5 (particulate matter with aerodynamic diameters Ͻ2.5 m) emissions from these categories are associated with EC and OC source profiles to generate California's speciated emissions. A BC inventory for California of 38,731 t/yr was comparable to the 33,281 t/yr estimated from a bottom-up global BC inventory. However, further examination showed substantial differences among subcategories, with the global inventory BC from fossil fuel combustion at two-thirds that from the California inventory and the remainder attributed to biomass burning. Major discrepancies were found for directly emitted OC, with the global inventory estimating more than twice that of the California inventory. Most of the discrepancy was due to differences in open biomass burning (wildfires and agricultural waste) for which carbon emissions are highly variable. BC and OC emissions are sensitive to the availability and variability of existing source profiles, and profiles more specific to fuels and operating conditions are needed to increase emission accuracy.

Journal of the Air & Waste Management Association, 2010

A relatively new mesoporous silica sorbent for environmental protection applications (i.e., mesop... more A relatively new mesoporous silica sorbent for environmental protection applications (i.e., mesoporous spherical-silica particles [MSPs]), was modified by N-[3-(trimethoxysilyl)propyl]ethylenediamine (EDA) solution and was tested for its potential in the separation of carbon dioxide ([CO.sub.2]) from flue gas. The [CO.sub.2] adsorption capacity of MSP and MSP(EDA) increased with temperature from 20 to 60 [degrees]C but decreased with temperature from 60 to 100

Journal of the Air & Waste Management Association, 2010

Seasonal odor and gas (ammonia [NH3], hydrogen sulfide [H2S], and carbon dioxide [CO2]) concentra... more Seasonal odor and gas (ammonia [NH3], hydrogen sulfide [H2S], and carbon dioxide [CO2]) concentrations and emission rates (OGCERs) from swine facilities are vital for providing accurate source emissions and reducing the uncertainty of setback distances on the basis of emission data. In this study, a repeated measurement experimental method and a split-block statistical model were used to obtain seasonal OGCER profiles from two types of swine grower-finisher rooms in Saskatchewan, Canada, over a 12-month period. The results indicate that the OGCERs were significantly affected by the sampling month and ambient temperature (P < 0.05), which indicates that monthly OGCERs should be measured and used as representative monthly or seasonal values in air dispersion models to reduce uncertainties in setback calculations. It was also found that the seasonal OGCERs from the rooms with fully slatted floors were 6.3-40.6% higher than those with partially slatted floors. The seasonal OGCERs (except for the NH3 concentrations in October, November, and January; the CO2 concentrations in August; and the CO2 emission rates in December) between these two rooms for each measuring month did not differ significantly (P > 0.05). The measured gas concentrations were generally below the permissible exposure limits (PELs) established by the Occupational Safety and Health Administration (OSHA) throughout the year except for the NH3 concentrations in cold weather (December, January, and February).

Atmosphere, 2018

In this study, an air mass (containing a cirrus cloud) was detected by light detection and rangin... more In this study, an air mass (containing a cirrus cloud) was detected by light detection and ranging (lidar) above São Paulo (Brazil) in June 2007 and tracked around the globe, thanks to Lagrangian calculations as well as ground-based and satellite observations. Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) data were also used to provide locations of occurrence of cirrus around the globe and extract their respective macro physical parameters (altitude and temperature). An analysis of the air mass history based on Lagrangian trajectories reveals that water coming from the Equator is channelized through the southern subtropical jet for weeks. In this case, the back-trajectories showed that the cirrus cloud detected at São Paulo was a mixture of air masses from two different locations: (1) the active convective area located around the Equator, with transport into the upper troposphere that promotes cirrus cloud formation; and (2) the South Pacific Ocean, wit...

Proceedings of the 16th International Congress of the Brazilian Geophysical Society&Expogef, 2019

Contents of this paper were reviewed by the Technical Committee of the 16 th International Congre... more Contents of this paper were reviewed by the Technical Committee of the 16 th International Congress of the Brazilian Geophysical Society and do not necessarily represent any position of the SBGf, its officers or members. Electronic reproduction or storage of any part of this paper for commercial purposes without the written consent of the Brazilian Geophysical Society is prohibited.

Energy Procedia, 2017

After the Ressacada Project experience acquired from 2011 to 2015 when PUCRS, UNESP and other ins... more After the Ressacada Project experience acquired from 2011 to 2015 when PUCRS, UNESP and other institutions conducted three controlled CO 2 release experiments, PETROBRAS, the national oil company that is sponsoring the project, has launched a new challenge to its partners. The company stimulated the implementation of a new Brazilian experimental site where there will be a deepening of studies in geologically more complex conditions and more challenging from a technological point of view. The choice of an area inside PUCRS campus, in Viamão-Rio Grande do Sul state, was motivated by a predominantly clay subsoil and the privileged location of the site in terms of ease logistics and security, which is required for a project of this size that houses high-tech equipment with significant cost. The CO 2 MOVE project started at 2015 with the subsurface characterization of the site and the assembly and manufacture of an automated system for CO 2 and gas tracers with injection capacity for 5 to 50 kg/day. Based on physical characterization studies and on numerical modeling that is being developed, the site infrastructure will be completed in the next months with the positioning of vertical injection wells, monitoring wells, and other equipment and monitoring mesh. Monitoring tools should be arranged in an area of approximately 100m 2 , occupying the entire region surrounding the injection wells. Fieldwork involving CO 2 injection and monitoring should have a 60 days duration of which 15 days are for preliminary surveys (pre-injection), 30 days for injection and CO 2 monitoring and the last 15 days for post-injection measurements. Following this work, the collected data will be analyzed in the university labs.

In this work, we present a variation of the technique CRDS (Cavity Ring-Down Spectroscopy) to obt... more In this work, we present a variation of the technique CRDS (Cavity Ring-Down Spectroscopy) to obtain simultaneously a multicomponent absorption spectrum in a broad visible range. This new approach uses the Supercontinuum (SC) spectrum (resulting from irradiation of nonlinear media by femtosecond lasers, or simply generated by compact sources) as a light source to illuminate the cavity. In this context it is described the features of the modules assembling a MC-SC-CRDS (Multicomponent Supercontinuum Cavity Ring-Down Spectroscopy): a set of high refletivity mirrors, the resonant cavity and the detection system. Some problems related to the multimode excitation, stray light, effective use of the dynamic range of the detector, the poor resolution of the instrument to resolve narrow absorption lines are issued. We present the absorption spectra of H 2 O (polyads 4ν, 4ν + δ) and O 2 (spin-forbidden b-X branch) measured simultaneously by this technique in the visible range and a comparison with the absorption lines based on HITRAN database is made to demonstrate the functionality of this method.

Optica Pura y Aplicada

We compare the performance of some available atmospheric models for the atmosphere of Sao Paulo (... more We compare the performance of some available atmospheric models for the atmosphere of Sao Paulo (Brazil) to be used in case of absence of radio-sounding data for the given day. We developed our own model (SPm) from historic radio-sounding data in order to create a local model. By performing inversions of lidar signals (distributed over a year), we could benchmark the performance of the models against radio-sounding data. SPm and ISA-15N show the smallest deviation and represent, therefore, the best fallback models for this southern latitude.

Lidar Technologies, Techniques, and Measurements for Atmospheric Remote Sensing X, 2014

Currently one of the main challenges in CO2 storage research is to grant the development, testing... more Currently one of the main challenges in CO2 storage research is to grant the development, testing and validation of accurate and efficient Measuring, Monitoring and Verification (MMV) techniques to be deployed at the final storage site, targeting maximum storage efficiency at the minimal leakage risk levels. For such task a mimetic sequestration site has been deployed in Florianopolis, Brazil, in order to verify the performance of monitoring plataforms to detect and quantify leakages of ground injected CO2, namely a Cavity Ring Down System (CRDS) - Los Gatos Research - an Eddy Covariance System (Campbell Scientific and Irgason) and meteorological tower for wind, humidity, precipitation and temperature monitoring onsite. The measurement strategy for detecting CO2 leakages can be very challenging since environmental and phytogenic influence can be very severe and play a role on determining if the values measured are unambiguous or not. One external factor to be considered is the amount of incoming solar radiation which will be the driving force for the whole experimental setup and following this reasoning the amount of aerosols in the atmospheric column can be a determinant factor influencing the experimental results. Thus the investigation of measured fluxes CO2 and its concentration with the aforementioned experimental instruments and their correlation with the aerosol data should be taken into account by means of satellite borne systems dedicated to measure aerosol vertical distribution and its optical properties, in this study we have selected CALIPSO and MODIS instrumentation to help on deriving the aerosol properties and CO2 measurements.

Lidar Technologies, Techniques, and Measurements for Atmospheric Remote Sensing X, 2014

The Latin American Lidar Network (LALINET) is the aerosol lidar network operating over South Amer... more The Latin American Lidar Network (LALINET) is the aerosol lidar network operating over South America. LALINET is now an operative network performing a schedule of routine measurements and, currently, is composed by 9 stations distributed over South America. The main objective of LALINET is to generate a consistent and statistically relevant database to enhance the understanding of the particle distribution over the continent and its direct and indirect influence on climate. The creation of an un-biased spatiotemporal database requires a throughout review of the network on two pillars: instrumentation and data processing. Because most of the LALINET systems are not series-produced instruments and, therefore, present large differences in configuration and capabilities, attempts for network harmonization and, consequently, optimization are mandatory. In this study a review of the current instrumental status of all LALINET systems is done and analyzed in detail in order to assess the potential performance of the network and to detect networking weaknesses.

Energy Procedia, 2014

Currently one of the main challenges in CO 2 storage research is the development, testing and val... more Currently one of the main challenges in CO 2 storage research is the development, testing and validation of accurate and efficient Measuring, Monitoring and Verification (MMV) techniques to be deployed at geological sequestration sites that are cost effective yet help minimize risk. This perspective motivated PETROBRAS, the National Oil Major in Brazil, through its R&D investments portfolio to prioritize research projects that would contribute to decreasing the technological gap in the area. The Company's periodic surveys indicated the lack of infrastructure, as well as expertise in CO 2 MMV, as two of the most critical issues at the national level. In order to bridge that gap, initial steps were taken in 2010 for the start-up and development of the first CO 2 MMV Field Lab in Brazil, fully sponsored by PETROBRAS, with a long term goal of enabling the ranking of the best, most costeffective MMV technology alternatives to be deployed at commercial large scale CCGS sites scheduled to be installed in the country. In addition to providing basic infrastructure to carry out the CO 2 injection and controlled release experiments, the facility was designed for the simultaneous testing of multiple measuring methodologies. Additional benefits of the initiative are the creation of expertise and the acceleration of the know-how in MMV in Brazil, as well as the development of a deeper and more

Brazilian Journal of Physics, 1999

We h a ve observed changes in the morphology of InP lms grown in epi-ready substrates and on patt... more We h a ve observed changes in the morphology of InP lms grown in epi-ready substrates and on patterns created by photo and plow-mode AFM lithography. These changes are attributed to di erent levels of contamination of the surface, which f a vor nucleation of clusters over a two-dimensional lm for the lithography-processed surface. The area of nucleation is smaller than the dimensions of the patterns created by lithography, so no size e ects due to the presence of the pattern could be observed. The lm morphologies exhibited well de ned exponents for system sizes smaller than 0.2 m but no de ned growth exponent.

Sensors, 2011

A multiwavelength, multicomponent CRDS gas sensor operating on the basis of a compact photonic cr... more A multiwavelength, multicomponent CRDS gas sensor operating on the basis of a compact photonic crystal fibre supercontinuum light source has been constructed. It features a simple design encompassing one radiation source, one cavity and one detection unit (a spectrograph with a fitted ICCD camera) that are common for all wavelengths. Multicomponent detection capability of the device is demonstrated by simultaneous measurements of the absorption spectra of molecular oxygen (spin-forbidden b-X branch) and water vapor (polyads 4v, 4v + δ) in ambient atmospheric air. Issues related to multimodal cavity excitation, as well as to obtaining the best signal-to-noise ratio are discussed together with methods for their practical resolution based on operating the cavity in a "quasi continuum" mode and setting long camera gate widths, respectively. A comprehensive review of multiwavelength CRDS techniques is also given.

Cirrus clouds with several important and climate-related applications are product of weather proc... more Cirrus clouds with several important and climate-related applications are product of weather processes, and hence their occurrence and macrophysical/optical properties can vary significantly over different regions of the world. In this sense, a few case studies of cirrus clouds observed at both subtropical and polar latitudes are examined. Observations are carried out in three stations: Sao Paulo (Brazil, 23.6°S/46.8°W) and Sta. Cruz de Tenerife (Spain, 28.5°N/16.3°W), being both subtropical sites, and the Belgrano II base (Argentina, 78ºS/35ºW) in the Antarctic continent. Active remote sensing (LIDAR) is used for profiling measurements, and cirrus clouds features are retrieved by using a recently proposed methodology. Local radiosounding profiles are also used for cirrus-temperature correlation analysis. Optical and macrophysical properties (COD-cloud optical depth, top/base heights and Lidar Ratio, mainly) of both the subtropical and polar cirrus clouds are reported. This study is...

Understanding the impact of cirrus cloud on modifying both the solar reflected and terrestrial em... more Understanding the impact of cirrus cloud on modifying both the solar reflected and terrestrial emitted radiations is crucial for climate studies. Unlike most boundary layer stratus and stratocumulus clouds that have a net cooling effect on the climate, high-level thin cirrus clouds have a warming effect on our climate. However, the satellites as GOES from the NOAA series are limited to the cloud top and its reflectivity or brightness temperature, without assessing accurately the optical depth or physical thickness. Other more recent sensors as MODIS are able to determine optical depths for aerosols and clouds but when related to cirrus they are still inaccurate. Research programs as First ISCCP, FIRE, HOIST, ECLIPS and ARM have concentrated efforts in the research of cirrus, being based mainly on the observations of combined terrestrial remote sensing and airplanes instruments. LIDARs are able to detect sub-visual cirrus cloud (SVCs) in altitudes above 15 km and estimate exactly the...

ABSTRACT A high sensitive Cavity Ring-Down Spectroscopy (CRDS) system is proposed to monitoring t... more ABSTRACT A high sensitive Cavity Ring-Down Spectroscopy (CRDS) system is proposed to monitoring the aerosol extinction coefficient in the city of São Paulo, Brazil. A continuous range of wavelengths varying from 645 and 675 nm is used to excite the cavity. This continuous range is provided from a fiber-based super continuum light source illuminating one end of the cavity at a repetition rate of 25 kHz. The signal through the cavity is selected by a spectrometer and then recorded by an iCCD camera. The reference measurement is performed under vacuum while the measurement for absorption/extinction is performed by sampling ambient air (preferably from an atmosphere containing aerosol particles) directly into the cavity. The first measurement performed with a volume of air with a relative humidity of around 54% and temperature of 295 K showed strong absorption peaks respectively at 647.7, 651.5 and 654.9 nm due to the presence of relatively high concentration of water vapor in the sampled air. In spectral windows that are free from molecular resonances of H2O (in our case 665−675 nm) the wavelength averaged rate of the energy loss determined in this way is 5.7 ± 0.3 E−8 per cm. The Rayleigh scattering theory yields a similar value of 5.3 E−8 per cm and the small discrepancy of about 4 E−9 per cm is likely caused by Mie scattering on residual dust particles. The resulting experimental spectra can be compared with results obtained by the Mie theory to estimate the respective size distribution of particles.

ABSTRACT The extinction-to-backscatter ratio (also called lidar ratio-LR) is an important paramet... more ABSTRACT The extinction-to-backscatter ratio (also called lidar ratio-LR) is an important parameter which provides information on the transmission and reflection properties of cirrus clouds and also on the ice crystal properties due to their dependence on the particle shape, size and orientation for the particles. In this study is showed an innovative method to obtain theLR for each cloud layer through iterative processes, applying a numerical routine developed at the Center for Lasers and Applications (CLA/IPEN-Brazil) in cooperation with the Laboratoire Amosphères, Milieus, Observations Spatiales, Institut Pierre Simon Laplace/Versailles-Saint Quentin University (LATMOS/IPSL-France). The resulting LR values were obtained based on measurements of the MSP (Metropolitan City of São Paulo) - lidar system, performed on 11th June 2007, comprehending 298 minutes separated in 7 distinct so called stationary periods. For the first four periods, was observed two distinct layers of clouds with LR values varying between 28±15 and 35 ± 18 sr for the first layer and 37±11srand 74±14 sr for the second, indicating the presence of both small and large ice crystals composed by solid and hollow columns in majority. The last 3 periods of measurements in turn presented a mono¬layer cloud with LR about 19±04 sr, what corresponds to a relatively small solid needles, plates and column crystals.

Atmospheric Measurement Techniques Discussions, 2013

This paper presents a methodology to calculate lidar ratios for distinct cirrus clouds that has b... more This paper presents a methodology to calculate lidar ratios for distinct cirrus clouds that has been developed and implemented for a site located in the Southern Hemisphere. The cirrus cloud lidar data processing aims to consider a large cloud variability and cirrus cloud monitoring through a robust retrieval process. Among cirrus features estimates for complex scenes that lidar systems can provide, we highlight cloud geometrical information and extinctionto-backscatter ratio (known as lidar ratio or LR). In general, direct information on cirrus cloud microphysics is difficult to derive because LR depends on the presence of ice crystals and their properties such as shape, size, composition and orientation of particles. An iterative process to derive a stable LR value has been proposed. One of the keys is to restrict the analysis to conditions allowing accurate multilayer events. This method uses nonparametric statistical approaches to identify stationary periods according to cloud features and variability. Measurements performed in the region of the metropolitan city of São Paulo (MSP) have been used to implement and test the methodology developed for cirrus cloud characterization. Good results are represented by examining specific cases with multilayer cirrus cloud occurrence. In addition to the geometrical parameters obtained, cirrus LR values were calculated for a single day ranging from 19 ± 01 sr to 74 ± 13 sr for 2 observed layers. This large difference in LR can indicate a mixture of ice crystal particles with different sizes and shapes in both layers of the cirrus clouds. Trajectory analyses indicate that both of these cloud layers can be associated with different air mass and should be considered as 2 distinct clouds in climatology. www.atmos-meas-tech.net/6/3197/2013/

Optica Pura y Aplicada, 2014

Nature Communications, 2011

Because of the potential impact on agriculture and other key human activities, efforts have been ... more Because of the potential impact on agriculture and other key human activities, efforts have been dedicated to the local control of precipitation. The most common approach consists of dispersing small particles of dry ice, silver iodide, or other salts in the atmosphere. Here we show, using field experiments conducted under various atmospheric conditions, that laser filaments can induce water condensation and fast droplet growth up to several µm in diameter in the atmosphere as soon as the relative humidity exceeds 70%. We propose that this effect relies mainly on photochemical formation of p.p.m.-range concentrations of hygroscopic Hno 3 , allowing efficient binary Hno 3 -H 2 o condensation in the laser filaments. Thermodynamic, as well as kinetic, numerical modelling based on this scenario semiquantitatively reproduces the experimental results, suggesting that particle stabilization by Hno 3 has a substantial role in the laser-induced condensation. close to Geneva (46°12' North, 6°5' East, 380 m above sea level). This location was chosen to get the benefit from the relatively warm water flow from the Lake of Geneva acting as a heat buffer, locally increasing the RH. As detailed in , data were acquired in a wide variety of atmospheric conditions: RH from 35 to 100%, temperature between 2 and 36 °C. Furthermore, experiments at all times of the day and the night ensured that both phases of increase and decrease of temperature and RH have been recorded.

Journal of the Air & Waste Management Association, 2010

Particulate black or elemental carbon (EC) (black carbon [BC]) and organic carbon (OC) affect cli... more Particulate black or elemental carbon (EC) (black carbon [BC]) and organic carbon (OC) affect climate, visibility, and human health. Several "top-down" and "bottom-up" global emission inventories for these components have compiled country-wide emission factors, source profiles, and activity levels that do not necessarily reflect local conditions. Recent estimates of global BC and OC emissions range from 8 to 24 and 33 to 62 Tg (10 12 g) per year, respectively. U.S. BC emissions account for 5.6% of the global total emissions. Uncertainties in global BC emission estimates are a factor of 2 or more. The U.S. National Emissions Inventory is well documented, but its major source categories are not easily related to EC-and OCemitting source subcategories. California's bottom-up emission inventory is easily accessible at many levels of detail and provides an example of how sources can be regrouped for speciated emission rates. PM 2.5 (particulate matter with aerodynamic diameters Ͻ2.5 m) emissions from these categories are associated with EC and OC source profiles to generate California's speciated emissions. A BC inventory for California of 38,731 t/yr was comparable to the 33,281 t/yr estimated from a bottom-up global BC inventory. However, further examination showed substantial differences among subcategories, with the global inventory BC from fossil fuel combustion at two-thirds that from the California inventory and the remainder attributed to biomass burning. Major discrepancies were found for directly emitted OC, with the global inventory estimating more than twice that of the California inventory. Most of the discrepancy was due to differences in open biomass burning (wildfires and agricultural waste) for which carbon emissions are highly variable. BC and OC emissions are sensitive to the availability and variability of existing source profiles, and profiles more specific to fuels and operating conditions are needed to increase emission accuracy.

Journal of the Air & Waste Management Association, 2010

A relatively new mesoporous silica sorbent for environmental protection applications (i.e., mesop... more A relatively new mesoporous silica sorbent for environmental protection applications (i.e., mesoporous spherical-silica particles [MSPs]), was modified by N-[3-(trimethoxysilyl)propyl]ethylenediamine (EDA) solution and was tested for its potential in the separation of carbon dioxide ([CO.sub.2]) from flue gas. The [CO.sub.2] adsorption capacity of MSP and MSP(EDA) increased with temperature from 20 to 60 [degrees]C but decreased with temperature from 60 to 100

Journal of the Air & Waste Management Association, 2010

Seasonal odor and gas (ammonia [NH3], hydrogen sulfide [H2S], and carbon dioxide [CO2]) concentra... more Seasonal odor and gas (ammonia [NH3], hydrogen sulfide [H2S], and carbon dioxide [CO2]) concentrations and emission rates (OGCERs) from swine facilities are vital for providing accurate source emissions and reducing the uncertainty of setback distances on the basis of emission data. In this study, a repeated measurement experimental method and a split-block statistical model were used to obtain seasonal OGCER profiles from two types of swine grower-finisher rooms in Saskatchewan, Canada, over a 12-month period. The results indicate that the OGCERs were significantly affected by the sampling month and ambient temperature (P < 0.05), which indicates that monthly OGCERs should be measured and used as representative monthly or seasonal values in air dispersion models to reduce uncertainties in setback calculations. It was also found that the seasonal OGCERs from the rooms with fully slatted floors were 6.3-40.6% higher than those with partially slatted floors. The seasonal OGCERs (except for the NH3 concentrations in October, November, and January; the CO2 concentrations in August; and the CO2 emission rates in December) between these two rooms for each measuring month did not differ significantly (P > 0.05). The measured gas concentrations were generally below the permissible exposure limits (PELs) established by the Occupational Safety and Health Administration (OSHA) throughout the year except for the NH3 concentrations in cold weather (December, January, and February).