D. A. Gouveia

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.

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.

Characterization of cirrus clouds in central Amazon (2.89ºS, 59.97ºW): firsts results from observations in 2011

espanolEn la region central de la Amazonia, en el ano 2011, se instalo una estacion lidar. Se encuentra ubicado a 30 km de Manaos, estado Amazona, Brasil, en la direccion de donde proviene el viento. El instrumento para medir la troposfera a distancia emplea un laser Nd-YAG, con potencia de 95 mJ a la longitud de onda de 355 nm. La recepcion es realizada con un telescopio de Cassegrain con 400 mm de diametro y 4000 mm de distancia focal. Durante el primer ano de mediciones se trabajo con un campo de vision estrecho permitiendo un valor razonable de la relacion senal ruido cerca de la tropopausa. El presente estudio se enfoca en la caracterizacion de nubes cirros tropicales observadas durante el primer ano de operacion (Febrero a Diciembre de 2011). Se adapto para las condiciones de este sistema lidar el algoritmo de deteccion de nubes desarrollado por Barja and Aroche (2001). Este fue empleado para determinar las alturas del tope y la base, y espesor geometrico. Para la determinacion del espesor optico de nubes cirros se empleo un metodo basado en el factor de transmitancia de la senal lidar. La ocurrencia del tipo de nubes cirros medida con lidar es cercana a 63 % con respecto al tiempo total de observacion. Estas se encuentran ubicadas entre 10 km y 16 km de altura. Los resultados encontrados concuerdan con los reportados por Sassen et al (2008) empleando datos de lidar CALIOP a borde de satelite CALIPSO. Tambien es resultado del presente trabajo que cerca del 26 % de los cirros fueron clasificados como cirros subvisibles ( 0.3). EnglishIn 2011 a UV Raman-Lidar station become operational in the central Amazon region. The instrument is installed 30 km up-wind from Manaus-AM and remotely senses the troposphere using a 95 mJ Nd-Yag laser at 355 nm. Receiving optics consists of a cassegrain telescope with 400 mm and 4000 mm focal length. During the first year of operation, a narrow field of view was used to allow a reasonable signal to noise ratio near the tropopause. This study focuses on the characterization of tropical cirrus clouds observed during the first year of operation (February to December 2011). A cloud detection algorithm developed by Barja and Aroche (2001) was adapted for this system and used to determine the cloud base and top heights, and cloud thickness. The method based on the lidar transmittance factor was used to derive the cirrus optical depth. The occurrence of cirrus clouds is about 63% of the total observation time, and these are located between 10 and 16 km height typically. This result agrees with those derived by Sassen et al (2008) from Calipso data. We also found that around 26% of all cirrus were subvisual cirrus ( 0.3).