Lidia Otero

Towards an instrumental harmonization in the framework of LALINET: dataset of technical specifications

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.

Monitoring volcanic ash in the atmosphere

Fil: Chouza, Fernando. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Instituto de Investigaciones Cientificas y Tecnicas para la Defensa. Centro de Investigacion en Laseres y Aplicaciones; Argentina

Fires, Smoke and Biomass Burning across South America, August 23, 2006

Since the advent of satellite imagery, it has become feasible to track the evolution of smoke plumes generated by biomass‐burning events. The creation of worldwide‐distributed aerosol monitoring networks as AERONET, made possible the characterization of the aerosol air masses observed by satellite instruments. This characterization looks forward a better understanding of role of aerosols in global radiative forcing and validation of aerosol‐oriented satellite products, between others. This work combines satellite imagery and AERONET data to study a biomass‐burning event. The episode located in the north of Argentina, Paraguay, Bolivia and Brazil was observed by a MODIS instrument inside AQUA satellite on August 23, 2006. Several AERONET stations were studied and combined with HYSPLIT back‐trajectories to obtain a more precise estimation of the origin of these air masses.

Aerosol monitoring with a lidar observation network in southern South America

In the southern South America, various types of aerosols have been observed including biomass burning aerosols from the Amazon region, flying ashes from the volcanic eruptions coming from the Andean Volcanic Belt, mineral dust from the Patagonian Desert, and air pollution aerosols from urban areas. To monitor such aerosols continuously, we developed a lidar observation network in Argentina and Chile. Eight lidars were installed in Argentina and one in Punta Arenas, Chile. Backscattering signals are measured at three wavelengths: 355, 532, and 1064 nm. Eight of those instruments are measuring depolarization ratio at 355 and 532 nm to detect non-spherical aerosols. In addition, four lidars are equipped Ramans channels and two high-spectral-resolution channels to measure backscattering and extinction coefficients quantitatively. Lidar operation, data analysis, and products release are implemented within the South American Environmental Risk Management Network (SAVER-Net) system, which was developed by a trinational project among Japan, Argentina, and Chile. Using lidar data, hazard information on the aerosol type and extinction coefficient at low altitude is provided for public in a near real time. In addition, plume height and qualitatively concentration for volcanic ashes are estimated. The information on volcanic ashes may be effectively used for advising aircraft landing and departing when volcanic eruptions occurs.

Method to Detect Molecular Ranges in Elastic Lidar Signal

espanolSe presenta un metodo para la deteccion de plumas de aerosoles o nubes en una senal lidar elastica, como tambien, la determinacion de la altura de capa limite atmosferica. El objetivo de este trabajo es discriminar plumas de aerosoles o nubes de rangos Rayleigh puros, como tambien, la determinacion de la altura de la capa limite atmosferica. Este metodo esta basado en el concepto denominado Rayleigh-fit, donde la senal elastica corregida en rango es ajustada con una senal lidar Rayleigh pura formada con datos de radiosondeo. Para ejecutar este algoritmo, solo es necesaria de promediacion temporal, y solo un parametro de entrada es necesario para la ejecucion del metodo. Se realiza un analisis del metodo con senales medidas de diferentes sistemas lidar y se muestran sus resultados y limitaciones. EnglishA method to detect aerosol plumes or clouds from an elastic lidar signal is presented, as well the determination of the atmospheric boundary layer height. It is based on the Rayleigh-fit concept, where the range-corrected elastic lidar signal is fitted with a pure-Rayleigh range-corrected lidar signal formed by radiosonde data. To run the algorithm, only temporal averaging has to be taken into account, and only one input parameter is needed. An analysis of the method is performed using real lidar data from different lidar system, showing the results and its limitations.

Measurement method of high spectral resolution lidar with a multimode laser and a scanning Mach–Zehnder interferometer

A simple high spectral resolution lidar technique using a multi-longitudinal mode laser is proposed for measuring aerosol extinction and backscattering coefficients. A scanning interferometer having the same free spectral range as the mode spacing of the laser is used to separate Rayleigh from Mie scattering. Scanning the interferometer in the span of one fringe, the lidar signals at the minimum and maximum Mie-scattering transmission are measured. The Rayleigh scattering signal is analyzed from these signals, and the aerosol extinction coefficient is derived. The interferometer transmittance for Mie scattering is calibrated with the reference signals taken with a portion of the transmitted laser beam.

Development of a high-spectral-resolution lidar for continuous observation of aerosols in South America

Continuous monitoring of aerosol profiles using lidar is helpful for a quasi-real-time indication of aerosol concentration. For instance, volcanic ash concentration and its height distribution are essential information for plane flights. Depolarization ratio and multi-wavelength measurements are useful for characterizing aerosol types such as volcanic ash, smoke, dust, sea-salt, and air pollution aerosols. High spectral resolution lidar (HSRL) and Raman scattering lidar can contribute to such aerosol characterization significantly since extinction coefficients can be measured independently from backscattering coefficients. In particular, HSRL can measure aerosol extinction during daytime and nighttime with a high sensitivity. We developed an HSRL with the iodine filter method for continuous observation of aerosols at 532nm in the northern region of Argentina in the framework of the South American Environmental Atmospheric Risk Management Network (SAVER.Net)/SATREPS project. The laser wavelength of the HSRL was controlled by a feedback system to tune the laser wavelength to the center of an iodine absorption line. The stability of the laser wavelength with the system satisfied the requirement showing very small systematic errors in the retrieval of extinction and backscatter.

Multi-wavelength scanning Raman lidar simulations for the Cherenkov Telescope Array observatory

This paper discusses the multi-wavelength scanning Raman lidar being built at Lidar Division, CEILAP (CITEDEF-CONICET) in the frame of the Argentinean CTA (Cherenkov Telescope Array) collaboration. CTA is an initiative to build the next generation of ground-based instruments to collect very high energy gamma-ray radiation (greater than a few tens of GeV). The atmospheric conditions are of major interest to CTA, and lidars are requested to acquire atmospheric profiles fast, accurately and in the line of sight of the event. Due to the expected low aerosol optical depth of the future site, the short observation period as well as the extension of the observation, an enhanced collection area is required. Based on this constraints, and energy laser pulse, a backscatter lidar signal simulation was performed to estimate the main characteristics of the system. To derive these features, a SNR (signal-to-noise ratio) was also simulated to derive the total number of mirrors to achieve a good quality signal over the whole tropopause. Raman capabilities were added in the UV and VIS wavelengths to retrieve the spectral characteristics of the aerosol extinction and the water vapor profile. The results of the simulation, and the main characteristics derived are shown.

Monitoring Aerosol Optical Properties in the ABL, Using Lidar System and Sunphotometer in Buenos Aires, Argentina

At the Lasers and Applications Research Center (CEILAP, CITEFA‐CONICET, (34°33′ S, 58°30′ W), located in an industrial suburb of the metropolitan area (Villa Martelli, Buenos Aires, Argentina), operates a multiwavelength lidar, based on a Nd:Yag laser (Continuum Surelite III P‐IV). This system emits in 1064, 532 and 355 nm simultaneously (10 Hz, 600 mJ @ 1064 nm) and allows the monitoring of the optical aerosols properties in the atmospheric boundary layer (ABL). On the same experimental site, an AERONET sunphotometer provides the AOT value. An analysis of boundary layer behaviour in some relevant days of March, from the years 2004 to 2006 is presented. On the days analyzed, no aerosols events and clouds were registered over the ABL. Evolutions of some characteristics of the ABL are presented, such as the height of the boundary layer, height of entrainment zone (EZ) and the entrainment flux ratio.

Aerosol and Water Vapor Raman Lidar System at CEILAP, Buenos Aires, Argentina. Case Study: November 07, 2006.

A multiwavelength backscatter LIDAR (Light Detection And Ranging) was developed and operates at Centro de Investigaciones en Laseres y Aplicaciones, CEILAP (CITEFA‐CONICET), (34.5 S and 58.5 W) to study the atmospheric properties such as the aerosol optical parameters, the boundary layer evolution, and the water vapor vertical distribution. The emission system is based on a Nd:YAG laser emitting at the fundamental, second and third harmonic wavelengths. The reception unit was upgraded to collect the atmospheric elastic and nitrogen Raman backscatters from the second and third harmonic wavelength and the water vapor Raman backscatter from the third harmonic wavelength. The information from all these channels give us enough information to derive the vertical distribution of the total to molecular backscatter, the backscatter to extinction ratio (lidar ratio) and the Angstrom coefficient. In addition, water vapor mixing ratio profile is also measured by using the Raman water vapor and nitrogen channels (408 ...