Analyzing the atmospheric boundary layer using high-order moments obtained from multiwavelength lidar data: impact of wavelength choice

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 proposedThis research has been supported by the Andalusian Regional Government (P12-RNM-618 2409 project), the Spanish Agencia Estatal de Investigación (AEI, CGL2016-81092- R, CGL2017-90884-REDT and CGL2017-83538-C3-1-R projects), the Spanish Ministry of Economy and Competitiveness (CGL2016- 81092-R, and CGL2017-90884-REDT projects), the European Union’s Horizon 2020 project (NACTRIS 2, grant no. 621654109), the University of Granada, the National Council for Scientific and Technological Development (CNPQ, 152156/2018-6, 432515/2018-6 and 150716/2017-6 projects), the São Paulo Research Foundation (FAPESP, grant no. 2015/12793-0), and the FEDER program for the University of Granada

Lidar Observations in South America. Part I - Mesosphere and Stratosphere

South America covers a large area of the globe and plays a fundamental function in its climate change, geographical features, and natural resources. However, it still is a developing area, and natural resource management and energy production are far from a sustainable framework, impacting the air quality of the area and needs much improvement in monitoring. There are significant activities regarding laser remote sensing of the atmosphere at different levels for different purposes. Among these activities, we can mention the mesospheric probing of sodium measurements and stratospheric monitoring of ozone, and the study of wind and gravity waves. Some of these activities are long-lasting and count on the support from the Latin American Lidar Network (LALINET). We intend to pinpoint the most significant scientific achievements and show the potential of carrying out remote sensing activities in the continent and show its correlations with other earth science connections and synergies. In Part I of this chapter, we will present an overview and significant results of lidar observations in the mesosphere and stratosphere. Part II will be dedicated to tropospheric observations

Lidar Observations in South America. Part II - Troposphere

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

Development of a microfluidic circuit for atmospheric analysis through ultra-short laser pulse micromachining

O presente trabalho apresenta um aperfeiçoamento e validação qualitativa de um método para obtenção de glioxal - GLI (gás) em escala laboratorial através de solução aquosa de GLI 40%, a qual também se aplica na obtenção de metilglioxal - MGLI em mesmas condições. As obtenções exitosas de GLI, bem como a provável aquisição da outra espécie serão utilizadas para testes futuros no microrreator. Em seguida, dois tipos de microcircuitos com misturadores foram propostos e produzidos para sistema bifásico (gás-líquido), sendo estes, um circuito Duplo - T com misturador do tipo serpentina e o microcircuito - II composto do Misturador de Quebra e Recombinação Rápida (MQRR). Os misturadores desenvolvidos foram capazes de diminuir o tamanho das bolhas formadas em certos fluxos aplicáveis à cinética de reação de um microrreator, a qual mediante a técnica de derivatização tornará possível a identificação e quantificação de GLI e MGLI na amostra gasosa. A técnica de ablação com laser de pulsos ultracurtos foi aplicada para a confecção dos microcircuitos propostos. Também foram desenvolvidos para esta técnica, melhorias na microusinagem de geometrias complexas em superfícies de vidro óptico de borosilicato - BK7, as quais apresentaram ótimos resultados. Posteriormente, foi implementada uma técnica de validação e análise das velocidades, tamanho e número de bolhas através de um sistema de captura de imagem (Embedded Supervisory Optical System \"ESOS\"). O sistema de captura validado, foi a principal ferramenta na caracterização e definição do tipo de circuito que melhor pode ser aplicado ao microrreator em função do seu volume máximo e o tempo de residência para a técnica de derivatização. Por fim, um laser randômico microfluídico foi desenvolvido com o mesmo processo de microusinagem em superfície translúcida, sendo apresentado como candidato para análise do material derivatizado contendo GLI na saída do microrreator.This work presents an improvement and qualitative validation of a method for obtaining glyoxal - GLY (gas), on a laboratory scale through a 40% aqueous solution of GLY, which is also applied in obtaining methylglioxal - MGLY under the same conditions. The successful obtainment of GLY, as well as the probable acquisition of the other species, will be used for future testing in microfluidic microreactors. For this, two types of microcircuits, with mixers, were proposed and produced for a two-phase system (gas-liquid), these being a Double - T circuit (with serpentine mixer) and the microcircuit - II (composed by Mixed Speed and Recombination MSAR). The mixers developed were able to reduce the size of the bubbles formed in certain flows applicable to the kinetics of the reaction of a microreactor, which, through the derivatization technique, will make it possible to identify and quantify GLY and MGLY in the gaseous sample. The ultra-short laser pulses ablation technique was applied to make the proposed microcircuits. Improvements in the micromachining of complex geometries on the surfaces of BK7 borosilicate optical glass were also developed for this technique, which presented excellent results. Subsequently, a technique of validating and analyzing speeds, size, and number of bubbles was implemented using an image capture system (Embedded Supervisory Optical System \"ESOS\"). The validated capture system was the main tool in the characterization and definition of the type of circuit that can best be applied to the microreactor due to its maximum volume and the residence time for the derivatization technique. Finally, a microfluidic random laser was developed with the same micromachining process on a translucent surface, being presented as a candidate for analysis of the derivatized material containing GLY at the outlet of the microreactor

Influence of a Biomass-Burning Event in PM2.5 Concentration and Air Quality: A Case Study in the Metropolitan Area of São Paulo

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

Lalinet Network Status

LALINET (Latin American Lidar Network) follows its goal to consolidation as a federative lidar network to provide regional coverage over Latin America in providing aerosol and greenhouse gas profiles following QA/QC protocols and promoting the development of researchers and students in atmopheric science field. We show recent results on different approaches for studying the optical properties of the atmosphere regarding aerosols at tropospheric and stratospheric level and greenhouse gas mixing ratio profiles followed by our recent support and validation efforts towards present and future satellite missions

Lalinet Network Status

LALINET (Latin American Lidar Network) follows its goal to consolidation as a federative lidar network to provide regional coverage over Latin America in providing aerosol and greenhouse gas profiles following QA/QC protocols and promoting the development of researchers and students in atmopheric science field. We show recent results on different approaches for studying the optical properties of the atmosphere regarding aerosols at tropospheric and stratospheric level and greenhouse gas mixing ratio profiles followed by our recent support and validation efforts towards present and future satellite missions