P. Ristori

LALINET: The First Latin American–Born Regional Atmospheric Observational Network

AbstractSustained and coordinated efforts of lidar teams in Latin America at the beginning of the twenty-first century have built the Latin American Lidar Network (LALINET), the only observational network in Latin America created by the agreement and commitment of Latin American scientists. They worked with limited funding but an abundance of enthusiasm and commitment toward their joint goal. Before LALINET, there were a few pioneering lidar stations operating in Latin America, described briefly here. Biannual Latin American lidar workshops, held from 2001 to the present, supported both the development of the regional lidar community and LALINET. At those meetings, lidar researchers from Latin America met to conduct regular scientific and technical exchanges among themselves and with experts from the rest of the world. Regional and international scientific cooperation has played an important role in the development of both the individual teams and the network. The current LALINET status and activities are...

The first ALINE measurements and intercomparison exercise on lidar inversion algorithms

The first coordinated effort to perform simultaneous lidar measurements in Latin America was carried out as a pilot campaign between 10 and 14 September 2012. Four lidar stations contributed to the campaign measurements: Manaus, Sao Paulo, Concepcion and Buenos Aires. Data from all four contributing stations were manually screened and a 1-h average cloud-free profile was selected from each one. These four elastic profiles were analyzed by four of the groups using their own elastic lidar algorithm. Here, the results for the particle backscatter coefficient are compared and discussed. We show that after five stages, the results have an agreement better than the typical uncertainty in the retrieval. Systematic errors found in different algorithms during the five stages of the exercise emphasize the need for analysis, measurements and data quality protocols. Difficulties involved in the coordination of the campaign and in the collaborative analysis are also highlighted.

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

Biomass burning aerosol detection over Buenos Aires City, August 2009

At the end of August 2009, a biomass burning aerosol intrusion event was detected at the Laser and Applications Research Center, CEILAP (CITEFA-CONICET) (34.5° S – 58.5° W) at Villa Martelli, in Buenos Aires, Argentina. This center has a sunphotometer from the AERONET-NASA global network, UV solar radiation sensors, a meteorological station and an aerosol lidar system. The aerosol origin was determined by means of back-trajectories and satellite images. This work studies the aerosol air mass optical characterization and their effect in UV solar radiation.

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.