Volcanic alert system by lightning detection using the WWLLN - ash cloud monitor

Electrical discharges are observed in many volcanic eruptions and they have often been used as indicators of such eruptions. Volcanic lightning is remarkably similar to those produced during thunderstorms and is called analogous to thunderstorm-like plume lightning. The WWLLN developed a program called "Ash Cloud Monitor" (ACM), in which alerts are issued for possible volcanic eruptions when lightning strokes are detected around a volcano. The ACM tool has demonstrated to be a very effective technique to be aware of volcanic eruptions. However, most of the alerts released by ACM belong to false alarms of volcanic activity, because, in general, the detected lightning is produced by thunderstorms near the volcano. In order to assess and improve the ACM to detect volcanic eruptions, reducing false alert emissions and improving the quick interpretation of them, we develop a web platform called GeorayosVolcanoAr with a new structure and a modified algorithm, with respect to the algorithm used by ACM, for the classification of alerts. The new algorithm considers an alert system with 3 levels: Red - Yellow - Green, with the Red alert being the highest level and decreasing towards Green. The Red alert was assigned to those volcanoes where only recorded lightning within a radius of 20 km or the lightning detected within a radius of 20 km is at least twice as much as that detected up to 100 km from the vent. The study focused on 32 volcanoes located in the Andes, close to the Argentine-Chilean border, and analyzed the results reported by the ACM network in terms of a climatological study of the lightning activity, thunderstorm days and predominant winds in that region. This analysis serves as a basis for a general recognition of the study zone in order to improve the interpretation of the distribution and generation of false alerts; as well as to help decision makers, among others, to have a reference that allows them to issue the warning.Fil: Baissac, Daiana Marlene. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; Argentina. Ministerio de Defensa; ArgentinaFil: Nicora, Maria Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; Argentina. Ministerio de Defensa; ArgentinaFil: Bali, Juan Lucas. Ministerio de Defensa. Instituto de Investigaciones Científicas y Técnicas para la Defensa; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Badi, Gabriela A.. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: Avila, Eldo Edgardo. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Measurements of natural deposition ice nuclei in Córdoba, Argentina

Ice nucleation in the atmosphere is of practical and fundamental importance since ice crystals influence the release of snow, rain and hail. Suspended aerosols in the atmosphere typically initiate freezing at temperatures below −15 °C; although occasionally freezing occurs at higher temperatures. In this work we describe an experimental device designed to measure the concentration of natural ice nuclei under controlled temperature and supersaturation conditions. The measurements were performed at Córdoba City, for temperatures between −15 °C and −30 °C and the sampled air was supersaturated with respect to ice and subsaturated with respect to liquid water; under these conditions the deposition ice nuclei were quantified. There are few studies reported in the literature regarding measurements of deposition ice nuclei concentration and, to our knowledge, there are no previous laboratory data of this kind of ice nuclei for T < −20 °C. The results show that the number of deposition ice nuclei increases at colder temperatures and higher supersaturations. These results are in general in good agreement with results previously reported by other authors. A fitting function which depends on temperature and supersaturation is proposed to parameterize the results obtained in the present work.Fil: Lopez, Maria Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Instituto de Física "Enrique Gaviola"; ArgentinaFil: Avila, Eldo Edgardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Instituto de Física "Enrique Gaviola"; Argentin

Deformations of frozen droplets formed at-40C

The optical properties of cirrus clouds are frequently computed with respect to various ice-crystal size distributions and shapes; small ice crystals are generally considered to be quasi-spherical. This approximation can lead to significant errors in the analysis of the in-situ microphysical data and also in the theoretical study of the radiative properties of cirrus clouds. Effective size and aspect ratio of the particles are the key parameters required to determine the optical parameters that are included in modeling and prediction of climate; their parameterizations need to be as accurate as possible. In this work, laboratory experiments were conducted to study the ice crystal shape formed from the freezing of water droplets at-40°C. Liquid and ice clouds were separately formed and sampled in a cloud chamber at-30 and-40°C, respectively. The effective water droplet diameter ranged from 8 to 20 μm, while the effective ice particle diameter ranged from 8 to 30 m. The average effective diameters were 11 μm for water drops and 14 μm for frozen droplets. The deformation of the frozen droplets was evident during inspection under microscope; bulges and spikes protuberances were found in many of the observed ice particles. The results show that the aspect ratio of the frozen droplets is 1.2. Copyright 2012 by the American Geophysical Union.Fil: Lopez, Maria Laura. Universidad Nacional de Córdoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; ArgentinaFil: Avila, Eldo Edgardo. Universidad Nacional de Córdoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentin

Suitable regions for assessing long term trends in lightning activity

The efficiency and stability of global lightning data are not yet sufficient to provide accurate estimates of long term trends in lightning activity. In contrast, regional lightning networks are generally both efficient and stable. Regions with a low level of interannual variability are well suited to the identification of trends in lightning activity. Satellite lightning data are used to identify countries in South America which display only mild interannual variability. These countries are candidates for regional studies of long term trends in lightning activity. These trends can be linked to climate change.Fil: Collier, A. B.. University of KwaZulu-Natal; SudáfricaFil: Burgesser, Rodrigo Exequiel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; ArgentinaFil: Avila, Eldo Edgardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentin

Measurements of electric charge separated during the formation of rime by the accretion of supercooled droplets

In these experiments, the electric charge carried by single particles ejected from the surface of a graupel particle growing by riming was measured. Simulated graupel pellets were grown by accretion of supercooled water drops, at temperatures ranging from-2 to-10 °C in a wind tunnel at air velocities between 5 and 10 m s-1, with the goal of studying the charging of graupel pellets under conditions of secondary ice crystal production (Hallett-Mossop mechanism). The graupel, and induction rings upstream and downstream of the graupel, were connected to electrometers and analyzing circuits of sufficient sensitivity and speed to measure, correlate and display individual charging events. The results suggest that fewer than 1% of the ejected particles carry a measurable electric charge (>2 fC). Further, it was observed that the graupel pellets acquire a positive charge and the average charge of a single splinter ejected is −14 fC. This mechanism of ejection of charged particles seems adequate to account for a positive charge of around 1 pC that individual precipitation particles ofmm- size could acquire in the lower part of the cloud, which in turn could contribute to the lower positive charge region of thunderstorms.Fil: Lighezzolo, Rafael Andres. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomia y Física. Sección Física. Grupo de Física de la Atmosfera; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; ArgentinaFil: Pereyra, Rodolfo Guillermo. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomia y Física. Sección Física. Grupo de Física de la Atmosfera; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; ArgentinaFil: Avila, Eldo Edgardo. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomia y Física. Sección Física. Grupo de Física de la Atmosfera; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentin

Spatial and time distribution of the flash rate over tropical Africa

The lightning flash rate over tropical Africa was analyzed using lightning data of two independent lightning detection systems, the World Wide Lightning Location Network and the Lightning Imaging Sensor. Spatial and time distributions of lightning activity were studied using different spatial and temporal scales. Results show a very localized high-lightning activity center on the west side of the Albertine Rift Mountain, located east of the Congo Basin, and substantial lightning activity in the center of the region. Both centers show low variations on the lightning activity throughout the year and a marked diurnal cycle with a maximum lightning activity in the local afternoon. A secondary lightning activity center was found over Lake Victoria, which has an annual variation similar to that of the Congo Basin lightning activity centers but does not show a marked diurnal cycle. The lightning activities observed seem to be strongly influenced by topography and are in agreement with the small temperature ranges and with the rainfall observed in the region.Fil: Burgesser, Rodrigo Exequiel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; ArgentinaFil: Nicora, Maria Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas para la Defensa. Centro de Investigación en Láseres y Aplicaciones; ArgentinaFil: Avila, Eldo Edgardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentin

The role of natural mineral particles collected at one site in Patagonia as immersion freezing ice nuclei

This work studies the role of mineral particles collected in the region of Patagonia (Neuquén, Argentina) as ice nuclei particles (INPs) by immersion freezing mode. The particle immersion-freezing ability was analyzed under laboratory conditions by using an established drop-freezing technique. Mineralogical composition was characterized by using X-ray diffraction and electron micro probe analysis. Dynamic light scattering was used to determine the grain size distribution of particles, while the N2 adsorption and methylene blue adsorption methods were applied to determine their specific surface area. Water droplets of different volumes containing different concentrations of particles were cooled until droplets were frozen. For all the analyzed drop volumes, an increase in the freezing temperature of the drops was observed with increasing dust concentration. In the same way, the freezing temperature increased when the drop volume was increased at constant dust concentration. Both behaviors were linked to the availability of active sites in the particles. A plateau in the freezing temperature was observed at high suspension concentration for all the drop volumes. This plateau was related to the aggregation of the particles when the suspension concentration was increased and to the consequent decrease in the number of active sites. The active sites per unit of surface area were calculated and reported. For the studied range of temperature, results are in agreement with those reported for different sites and particles. From the chemical and morphological analysis of the particle components and the results obtained from the literature, it was concluded that even though montmorillonite was the main mineral in the collected sample, the accessory minerals deserve to be analyzed in detail in order to know if they could be responsible for the ability of the collected soil particles to act as INPs. Considering that the region of Patagonia has been identified as an important source of natural mineral particles in the atmosphere, it is important to analyze the ability of these particles to act as INP. As far as we know, this is the first study carrying out this investigation.Fil: Lopez, Maria Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; ArgentinaFil: Borgnino Bianchi, Laura Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Avila, Eldo Edgardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentin

The growth of ice particles in a mixed phase environment based on laboratory observations

This paper describes new laboratory observations about the size evolution of ice crystals and cloud droplets immersed in a mixed-phase cloud. The experiments were performed by using a cloud chamber facility for three temperatures − 6 °C, − 10 °C and − 20 °C, in order to explore the basic crystal growth habits (columns and hexagonal plates). The sizes of the cloud droplets, ice-columns and hexagonal ice-plates were examined for growth times between 50 and 300 s. The results show evidence that after ice crystal nucleation, the cloud droplets reduce gradually their sizes by the evaporation process; while the ice crystals grow as a consequence of the water vapor diffusion process. The ice crystal growths at different temperatures were compared with the results reported by other authors. The experimental data were also compared with a theoretical model of the growth rate of ice crystals. It was observed that the numerical model provides a description of the ice columns' growth in fairly good agreement with the laboratory observations, while it predicts that the hexagonal plates evolve with maximum sizes larger than those observed in the experiments. In general, it has been noted that the results obtained from the model are very sensitive to the parameter that denotes the ratio between the condensation coefficient for the basal face and prism face. It is a critical coefficient that needs to be carefully addressed in cloud modeling.Fil: Castellano, Nesvit Edit. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Avila, Eldo Edgardo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; ArgentinaFil: Burgesser, Rodrigo Exequiel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; ArgentinaFil: Saunders, Clive P.R.. University of Manchester; Reino Unid

Actividad eléctrica asociada a la erupción del complejo volcánico Cordón Caulle durante 2011

Se realizó un estudio de la actividad eléctrica generada por la erupción del complejo volcánico Cordón Caulle en junio de 2011 utilizando datos de descargas eléctricas detectadas por la red World Wide Lightning Location Network. La actividad eléctrica observada se corresponde a descargas eléctricas generadas en la pluma volcánica con una buena correlación entre la cantidad de descargas y la altura de la misma. Aunque la actividad eléctrica detectada fue baja, los resultados están de acuerdo con los obtenidos por estudios previos y muestran que puede ser usada como un indicador de la actividad volcánica. Además muestra la factibilidad de utilizar la red para una detección temprana de erupciones volcánicas.Fil: Nicora, Maria Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégicos para la Defensa; Argentina;Fil: Burgesser, Rodrigo Exequiel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET - Córdoba. Instituto de Fisica Enrique Gaviola; Argentina;Fil: Rosales, Alejandro. Universidad Nacional de la Patagonia; Argentina;Fil: Quel, Eduardo Jaime. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégicos para la Defensa; Argentina;Fil: Avila, Eldo Edgardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - Conicet - Cordoba. Instituto de Fisica Enrique Gaviola; Argentina