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.

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.

The city of Comodoro Rivadavia, in the province of Chubut, is located on the shores of the Argentinean Sea, in the central zone of the San Jorge Basin. Its climate is arid with little rainfall. In this work, the aerosol optical data of the aerosols of the AERONET/NASA network station that is installed in the monitoring station (45,792o S; 67,463o W) of the General Enrique Mosconi International Airport are analyzed statistically and correlated the wind direction resultsthat affect the city by 2015. It is mostly affected by winds from the West quadrant from the mountain range, and windsfrom the East quadrant from the sea. These two wind directions cause transport of two types of aerosols: marine and dust. To exemplify the characteristics of the aerosols mobilized by these two wind directions, the measurements of the solar photometer are studied for January 21th and 22th, 2015. The optical characteristics of the suspended aerosols in the atmosphere are determined for those days.

Globally consistent measurements of airborne metal concentrations in fine particulate matter (PM2.5) are important for understanding potential health impacts, prioritizing air pollution mitigation strategies, and enabling global chemical transport model development. PM2.5 filter samples (N ~ 800 from 19 locations) collected from a globally distributed surface particulate matter sampling network (SPARTAN) between January 2013 and April 2019 were analyzed for particulate mass and trace metals content. Metal concentrations exhibited pronounced spatial variation, primarily driven by anthropogenic activities. PM2.5 levels of lead, arsenic, chromium, and zinc were significantly enriched at some locations by factors of 100–3000 compared to crustal concentrations. Levels of metals in PM2.5 and PM10 exceeded health guidelines at multiple sites. For example, Dhaka and Kanpur sites exceeded the US National Ambient Air 3-month Quality Standard for lead (150 ng m−3). Kanpur, Hanoi, Beijing and Dhaka sites had annual mean arsenic concentrations that approached or exceeded the World Health Organization’s risk level for arsenic (6.6 ng m−3). The high concentrations of several potentially harmful metals in densely populated cites worldwide motivates expanded measurements and analyses.

Gravity wave (GW) activity is analyzed using temperature (T) data retrieved from a Rayleigh light detection and ranging (lidar) at Rio Gallegos, Argentina (51.6 degrees S, 69.3 degrees W). GW characteristics are derived from 302 nights of observations providing more than 1,018hr of high-resolution lidar data between 20- and 56-km height from August 2005 to December 2015. T measurements are performed by a Differential Absorption Lidar instrument. This lidar was the southernmost outside Antarctica until the end of 2017. Rio Gallegos is an exceptional place to observe large amplitude GW. Every lidar measurement is classified according to its relative position to the polar vortex. The lidar measurements are compared with collocated Sounding of the Atmosphere using Broadband Emission Radiometry and Global Positioning System-Radio Occultation data. The different instruments show different windows of the GW spectrum, providing complementary observations. In general, the geometric mean of the specific GW potential energy (PE) is larger during winter and spring than during summer and autumn. The largest geometric mean of PE is found inside the vortex and decreases monotonically at its edge, outside it and when there is no vortex. The same behavior is observed with satellite data. On average, it can be seen that lidar observations provide larger PE values than limb sounding measurements. From a Morlet continuous wavelet transform analysis, three distinct modes are captured from Sounding of the Atmosphere using Broadband Emission Radiometry and from Global Positioning System-Radio Occultation data at the upper and lower stratosphere, respectively. In particular, a systematic 3.5- to 4-year oscillation, possibly related to El Nino-Southern Oscillation is observed.

LALINET is expanding regionally to guarantee spatial coverage over South and Central Americas. One of the network goals is to obtain a set of regional representative aerosol optical properties such as particle backscatter, extinction and lidar ratio. Given the North-South extension and influence of distinct airmass circulation patterns it is paramount to distinguish these optical parameters in order to gain better perfomance in radiation transfer models. A set of lidar ratio data is presented.

A tropospheric lidar system was installed in Punta Arenas, Chile (53.13°S, 70.88°W) in September 2016 under the collaboration project SAVERNET (Chile, Japan and Argentina) to monitor the atmosphere. Statistical analyses of the clouds and aerosols behavior and some cases of dust detected with lidar, at these high southern latitude and cold environment regions during three months (austral spring) are discussed using information from satellite, modelling and solar radiation ground measurements.

The long-term evolution of total ozone column inside the Antarctic polar vortex is investigated over the 1980-2017 period. Trend analyses are performed using a multilinear regression (MLR) model based on various proxies for the evaluation of ozone interannual variability (heat flux, quasi-biennial oscillation, solar flux, Antarctic oscillation and aerosols). Annual total ozone column measurements corresponding to the mean monthly values inside the vortex in September and during the period of maximum ozone depletion from 15 September to 15 October are used. Total ozone columns from the Multi-Sensor Reanalysis version 2 (MSR-2) dataset and from a combined record based on TOMS and OMI satellite datasets with gaps filled by MSR-2 (1993-1995) are considered in the study. Ozone trends are computed by a piece-wise trend (PWT) proxy that includes two linear functions before and after the turnaround year in 2001 and a parabolic function to account for the saturation of the polar ozone destruction. In order to evaluate average total ozone within the vortex, two classification methods are used, based on the potential vorticity gradient as a function of equivalent latitude. The first standard one considers this gradient at a single isentropic level (475 or 550 K), while the second one uses a range of isentropic levels between 400 and 600 K. The regression model includes a new proxy (GRAD) linked to the gradient of potential vorticity as a function of equivalent latitude and representing the stability of the vortex during the studied month. The determination coefficient (R-2) between observations and modelled values increases by similar to 0.05 when this proxy is included in the MLR model. Highest R-2 (0.92-0.95) and minimum residuals are obtained for the second classification method for both datasets and months. Trends in September over the 2001-2017 period are statistically significant at 2 sigma level with values ranging between 1.84 +/- 1.03 and 2.83 +/- 1.48DUyr(-1) depending on the methods and considered proxies. This result confirms the recent studies of Antarctic ozone healing during that month. Trends from 2001 are 2 to 3 times smaller than before the turnaround year, as expected from the response to the slowly ozonedepleting substances decrease in polar regions. For the first time, significant trends are found for the period of maximum ozone depletion. Estimated trends from 2001 for the 15 September-15 October period over 2001-2017 vary from 1.21 +/- 0.83 to 1.96DU +/- 0.99 yr(-1) and are significant at 2 sigma level. MLR analysis is also applied to the ozone mass deficit (OMD) metric for both periods, considering a threshold at 220DU and total ozone columns south of 60 degrees S. Significant trend values are observed for all cases and periods. A decrease of OMD of 0.86 +/- 0.36 and 0.65 +/- 0.33 Mt yr(-1) since 2001 is observed in September and 15 September-15 October, respectively. Ozone recovery is also confirmed by a steady decrease of the relative area of total ozone values lower than 175DU within the vortex in the 15 September-15 October period since 2010 and a delay in the occurrence of ozone levels below 125 DU since 2005.

LALINET lidar stations were used to track down aerosols generated over Amazon region and transported over the continent. These data were merged with collocated Aeronet stations in order to help in their identification together with HYSPLIT simulations. The results show potential indication of how aerosol can age in their long transport over regions South and Westward from the source areas by change of their optical properties.

El humo provocado por una importante quema de biomasa en la provincia de Chubut, cerca del Parque Nacional Los Alerces, en febrero de 2015, fue trasportado por efecto de los vientos a diferentes zonas de la Patagonia. En este trabajo se presenta la detección de este evento sobre la ciudad de Neuquén por la estación de monitoreo atmosférico instalada en el Aeropuerto Internacional de Neuquén por CITEDEF y operada por personal del Servicio Meteorológico Nacional. Las mediciones realizadas con el sistema lidar muestra las alturas de las distintas capas de aerosoles y el fotómetro solar de la red AERONET/NASA (AErosol RObotic NETwork) detectó valores altos de espesor óptico de aerosoles. Las imágenes satelitales muestran que el humo llegó a la ciudad el 18 de febrero quedando en suspensión por varios días.

El humo provocado por una importante quema de biomasa en la provincia de Chubut, cerca del Parque Nacional Los Alerces, en febrero de 2015, fue trasportado por efecto de los vientos a diferentes zonas de la Patagonia. En este trabajo se presenta la detección de este evento sobre la ciudad de Neuquén por la estación de monitoreo atmosférico instalada en el Aeropuerto Internacional de Neuquén por CITEDEF y operada por personal del Servicio Meteorológico Nacional. Las mediciones realizadas con el sistema lidar muestra las alturas de las distintas capas de aerosoles y el fotómetro solar de la red AERONET/NASA (AErosol RObotic NETwork) detectó valores altos de espesor óptico de aerosoles. Las imágenes satelitales muestran que el humo llegó a la ciudad el 18 de febrero quedando en suspensión por varios días.

The atmospheric remote monitoring systems are essentials to understand the dynamic phenomena that occur in our atmosphere. In December 2016 a MAX-DOAS (Multi-AXis DOAS) instrument - called Pandora - that allows to quantify the ozone total column concentration among other atmospheric parameters, was installed in the Laser and Applications Research Center (CEILAP), Institute of Scientific and Technical Research for Defense (CITEDEF-MINDEF), Villa Martelli, Buenos Aires province. The system is based on the DOAS (Differential Optical Absorption Spectroscopy) technique and provides information about the daily and seasonal evolution of the gas under study. Measurements carry out by this instrument and inter-comparisons with data retrieved by a Dobson spectrophotometer of the National Meteorological Service (SMN)-located in Villa Ortuzar, CABA - and satellite data are presented.

On April 20th, 2017, a new sunphotometer of the AERONET - NASA network was installed inPilar, province of Cordoba, at the dependencies of the National Meteorological Service in order to measure the aerosol load of the region and especially to detect the biomass burning events that affect the center and north of the territory, and subsequently arrive to the province of Buenos Aires and La Pampa due to the wind transport. Afterinstalling this new instrument, the network has now 7 sunphotometerin the country, performing sistematic measurements. The first equipment was installed at CEILAP-UNIDEF (MINDEF-CONICET) - CITEDEF, on October 17th, 1999 in Buenos Aires. In this work the results obtained from a statistical analysis of the measurements from the 7 active stations are presented: CEILAP-BA, CEILAP-RG, CEILAP-Comodoro, CEILAP-Bariloche, CEILAP-Neuquen, Trelew and Pilar-Cordoba, to determine the monthly averaged values, aerosol optical depth tendencies, Angstrom coefficient and classification of the typical aerosol-suspended type for each station.

Un importante incendio forestal ocurrió en la provincia de Chubut a comienzos del año 2015. El incendio se inició el 15 de febrero en la zona de Cholila y duró hasta la llegada de las lluvias a principios de abril. Fue afectada una superficie aproximada de 41 000 hectáreas de bosques patagónicos vírgenes. Densas plumas de humo fueron llevadas por los vientos cubriendo gran parte de la Patagonia. El objetivo de este trabajo es estudiar el transporte de los aerosoles generados por este evento y su caracterización. Se presentan las mediciones registradas en las ciudades de Trelew (43° 15’ 00" S 65° 18’ 32" O, 15 m snm) y Comodoro Rivadavia (45° 47’ 31" S 67° 27’ 46" O, 49 m snm). En ambas ciudades se encuentran instalados fotómetros solares que pertenecen a la red AERONET – NASA. Estos instrumentos pasivos detectaron el 1 de marzo de 2015 elevados valores de espesor óptico de aerosoles para la región, (0,2 en la región visible), un coeficiente de Ångstrӧm entre 1,5 y 2, y una distribución en tamaño de partículas, dominando el modo fino, con un radio entre 0,1 y 1 μm. Todas las mediciones tienen valores que son consistentes con la presencia de humo. En Comodoro Rivadavia, además, se encuentra instalado un sistema de teledetección activo denominado lidar, que ha registrado el paso de las plumas de humo en la ciudad. El equipo tiene una resolución espacial de 7,5 m en la vertical y 10 s en la temporal. Las mediciones dejan ver capas de aerosoles entre los 1,5 y 7 km. Los registros en tierra fueron corroborados por imágenes satelitales TERRA y AQUA, por retrotrayectorias obtenidas de NOAA HYSPLIT MODEL y por patrones de circulación de viento en la región de NOAA/ESRL (NCEP/NCAR).

Exposure to ambient fine particulate matter (PM2.5) is a leading risk factor for the global burden of disease. However, uncertainty remains about PM2.5 sources. We use a global chemical transport model (GEOS-Chem) simulation for 2014, constrained by satellite-based estimates of PM2.5 to interpret globally dispersed PM2.5 mass and composition measurements from the ground-based surface particulate matter network (SPARTAN). Measured site mean PM2.5 composition varies substantially for secondary inorganic aerosols (2.4-19.7 mu g/m(3)), mineral dust (1.9-14.7 mu g/m(3)), residual/organic matter (2.1-40.2 mu g/m(3)), and black carbon (1.0-7.3 mu g/m(3)). Interpretation of these measurements with the GEOS-Chem model yields insight into sources affecting each site. Globally, combustion sectors such as residential energy use (7.9 mu g/m(3)), industry (6.5 mu g/m(3)), and power generation (5.6 g/m(3)) are leading sources of outdoor global population-weighted PM2.5 concentrations. Global population-weighted organic mass is driven by the residential energy sector (64%) whereas population-weighted secondary inorganic concentrations arise primarily from industry (33%) and power generation (32%). Simulation-measurement biases for ammonium nitrate and dust identify uncertainty in agricultural and crustal sources. Interpretation of initial PM2.5 mass and composition measurements from SPARTAN with the GEOS-Chem model constrained by satellite-based PM2.5 provides insight into sources and processes that influence the global spatial variation in PM2.5 composition.

LiRIC is an inversion procedure frequently used in the EARLINET network that is able to obtain vertical aerosol concentration profiles, using measurements from two instruments: Lidar and sun photometer. In this paper, we propose a reimplementation of that algorithm in the free language Python. We also did some synthetic scenarios studies which shows the robustness and the proper functioning of the tool. Finally, we proceeded with a study in a real case scenario, under a registered event of biomass burning in the monitoring station of Villa Martelli.

A new analysis of the dataset from the Pierre Auger Observatory provides evidence for anisotropy in the arrival directions of ultra-high-energy cosmic rays on an intermediate angular scale, which is indicative of excess arrivals from strong, nearby sources. The data consist of 5514 events above 20 EeV with zenith angles up to 80 deg recorded before 2017 April 30. Sky models have been created for two distinct populations of extragalactic gamma-ray emitters: active galactic nuclei from the second catalog of hard Fermi-LAT sources (2FHL) and starburst galaxies from a sample that was examined with Fermi-LAT. Flux-limited samples, which include all types of galaxies from the Swift-BAT and 2MASS surveys, have been investigated for comparison. The sky model of cosmic-ray density constructed using each catalog has two free parameters, the fraction of events correlating with astrophysical objects and an angular scale characterizing the clustering of cosmic rays around extragalactic sources. A maximum-likelihood ratio test is used to evaluate the best values of these parameters and to quantify the strength of each model by contrast with isotropy. It is found that the starburst model fits the data better than the hypothesis of isotropy with a statistical significance of 4.0 sigma, the highest value of the test statistic being for energies above 39 EeV. The three alternative models are favored against isotropy with 2.7-3.2 sigma significance. The origin of the indicated deviation from isotropy is examined and prospects for more sensitive future studies are discussed.