Search results for "lcsh:QC801-809"
showing 10 items of 42 documents
The relationship between the Sahelian and previous 2nd Guinean rainy seasons: a monsoon regulation by soil wetness?
2002
The correlation of 0.61 found between observed July–September Sahelian rainfall in year 0 and September–November Guinean rainfall in year - 1, led us to explore the statistical relationships between precipitation, soil moisture and near surface Moist Static Energy (MSE) gradients in West Africa. These analyses were performed over successive 30-year periods and specifically, the most recent period between 1968–1998. It is shown from observations, National Centers for Environmental Predictions and National Center for Atmospheric Research (NCEP/NCAR) reanalyses and from the Global Soil Wetness Project (GSWP) database, that wet Sahelian rainy seasons are preceded by abnormally wet soils over th…
Georeferenced cartography dataset of the La Fossa crater fumarolic field at Vulcano Island (Aeolian Archipelago, Italy): conversion and comparison of…
2011
The present study illustrates the procedures applied for the coordinate system conversion of the historical fumarole positions at La Fossa crater, to allow their comparison with newly acquired global positioning system (GPS) data. Due to the absence of ground control points in the field and on both the old Gauss Boaga and the new UTM WGS 1984 maps, we had to model the transformation errors between the two systems using differential GPS techniques. Once corrected, the maps show a residual Easting shifting, due to erroneous georeferencing of the original base maps; this is corrected by morphological comparative methods. The good correspondence between the corrected positions of the historical…
Recent advances in ground-based ultraviolet remote sensing of volcanic SO2 fluxes
2011
Measurements of volcanic SO2 emission rates have been the mainstay of remote-sensing volcanic gas geochemistry for almost four decades, and they have contributed significantly to our understanding of volcanic systems and their impact upon the atmosphere. The last ten years have brought step-change improvements in the instrumentation applied to these observations, which began with the application of miniature ultraviolet spectrometers that were deployed in scanning and traverse configurations, with differential optical absorption spectroscopy evaluation routines. This study catalogs the more recent empirical developments, including: ultraviolet cameras; wide-angle field-of-view differential …
First multi-GAS based characterisation of the Boiling Lake volcanic gas (Dominica, Lesser Antilles)
2013
We used a Multi-component Gas Analyser System (Multi-GAS) to measure, for the very first time, the composition (H2O, CO2, H2S, SO2) of the volcanic gas plume issuing from the Boiling Lake, a vigorously degassing, hot (T ~ 80-90°C) volcanic lake in Dominica, West Indies. The Multi-GAS captured in-plume concentrations of H2O, CO2 and H2S were well above those typical of ambient atmosphere, while no volcanic SO2 was detected (<0.05 ppm). These were used to derive the Boiling Lake plume characteristic ratios of CO2/H2S (5.2±0.4) and H2O/CO2 (31.4±6). Assuming that other volcanic gas species (e.g., HCl, CO, H2, N2, etc.) are absent in the plume, we recalculated a (air-free) composition fo…
Passive degassing at Nyiragongo (D.R. Congo) and Etna (Italy) volcanoes
2014
Volcanoes are well known as an impressive large natural source of trace elements into the troposphere. Etna (Italy) and Nyiragongo (D.R. Congo) are two stratovolcanoes located in different geological settings, both characterized by persistent passive degassing from their summit craters. Here, we present some results on trace element composition in volcanic plume emissions, atmospheric bulk deposition (rainwater) and their uptake by the surrounding vegetation, with the aim to compare and identify differences and similarities between these two volcanoes. Volcanic emissions were sampled by using active filter-packs for acid gases (sulfur and halogens) and specific teflon filters for particulat…
Trace elements mobility in soils from the active hydrothermal area of Nisyros (Greece)
2014
Nisyros Island, Greece, is a stratovolcano known for its intense hydrothermal activity. On June 2013, during a multidisciplinary field campaign, soil samples were collected in the caldera area to determinate the main mineralogical paragenesis and to investigate the distribution of trace elements concentrations and the possible relationship to the contribution of deep originated fluids. Soil samples were analysed with XRD and for the chemical composition of their leachable (deionized water) and near total (microwave digestion) fraction both for major and trace elements. All data were compared to a local background soil. The results allow to divide the samples in 2 groups: Lakki Plain and Ste…
Vulcamera: a program for measuring volcanic SO2 using UV cameras
2011
We report here on Vulcamera, a stand-alone program for the determination of volcanic SO2&nbsp; fluxes using ultraviolet cameras. The code enables field image acquisition and all the required post-processing operations.<br />
Effects of the 6th September 2002 earthquake: damage amplification in the south-eastern sector of Palermo explained by GIS technology
2009
During the 6th September 2002 earthquake the highest damage level in Palermo was observed in the SE sector. This is a recent urbanization area where reinforced concrete structures predominate. A detailed analysis of soil properties in Palermo was carried out by City-GIS to investigate a possible role of nearsurface geology on earthquake effects. City-GIS is a tool dedicated to natural hazard evaluation in urban areas. The availability of high density of well log data (stratigraphic and geotechnical) allowed a realistic modeling of surface geology and physical-mechanical properties that control the seismic response. In wide zones of the above mentioned sector of…
The classification of submerged vegetation using hyperspectral MIVIS data
2009
The aim of this research is to use hyperspectral MIVIS data to map the Posidonia oceanica prairies in a coastal lagoon (Stagnone di Marsala). It is approximately 12 km long and 2 km wide and is linked to the open sea by two shallow openings. This environment is characterised by prairies of phanerogams, the most common of which is Posidonia oceanica, an ideal habitat for numerous species of fish, molluscs and crustaceans. A knowledge of the distribution of submerged vegetation is useful to monitor the health of the lagoon. In order to classify the MIVIS imagery, the attenuation effects of the water column have been removed from the signal using Lyzenga’s technique. A comparison between class…
Recurrence time distribution and temporal clustering properties of a cellular automaton modelling landslide events
2018
Abstract. Reasonable prediction of landslide occurrences in a given area requires the choice of an appropriate probability distribution of recurrence time intervals. Although landslides are widespread and frequent in many parts of the world, complete databases of landslide occurrences over large periods are missing and often such natural disasters are treated as processes uncorrelated in time and, therefore, Poisson distributed. In this paper, we examine the recurrence time statistics of landslide events simulated by a cellular automaton model that reproduces well the actual frequency-size statistics of landslide catalogues. The complex time series are analysed by varying both the threshold…