Search results for "SOI"
showing 10 items of 4823 documents
Ice nucleation properties of the most abundant mineral dust phases
2008
[1] The ice nucleation properties of the nine most abundant minerals occurring in desert aerosols (quartz, albite, microcline, kaolinite, montmorillonite, illite, calcite, gypsum, and hematite) were investigated by environmental scanning electron microscopy (ESEM). In this instrument, the pure minerals are exposed to water vapor at variable pressures and temperatures. The crystallization of ice on the mineral particles is observed by secondary electron imaging, and the supersaturation for an activated particle fraction of 1–3% is determined as function of temperature. In all experiments, condensation of water prior to ice formation was not observed within detectable limits, even at water su…
Optical properties of deep glacial ice at the South Pole
2006
We have remotely mapped optical scattering and absorption in glacial ice at the South Pole for wavelengths between 313 and 560 nm and depths between 1100 and 2350 m. We used pulsed and continuous light sources embedded with the AMANDA neutrino telescope, an array of more than six hundred photomultiplier tubes buried deep in the ice. At depths greater than 1300 m, both the scattering coefficient and absorptivity follow vertical variations in concentration of dust impurities, which are seen in ice cores from other Antarctic sites and which track climatological changes. The scattering coefficient varies by a factor of seven, and absorptivity (for wavelengths less than ∼450 nm) varies by a fact…
Geogenic and atmospheric sources for volatile organic compounds in fumarolic emissions from Mt. Etna and Vulcano Island (Sicily, Italy)
2012
[1] In this paper, fluid source(s) and processes controlling the chemical composition of volatile organic compounds (VOCs) in gas discharges from Mt. Etna and Vulcano Island (Sicily, Italy) were investigated. The main composition of the Etnean and Volcano gas emissions is produced by mixing, to various degrees, of magmatic and hydrothermal components. VOCs are dominated by alkanes, alkenes and aromatics, with minor, though significant, concentrations of O-, S- and Cl(F)-substituted compounds. The main mechanism for the production of alkanes is likely related to pyrolysis of organic-matter-bearing sediments that interact with the ascending magmatic fluids. Alkanes are then converted to alken…
Variation of H2O/CO2and CO2/SO2ratios of volcanic gases discharged by continuous degassing of Mount Etna volcano, Italy
2008
[1] We applied the Multi-GAS technique to measure compositions of the volcanic plumes continuously discharged from summit craters of Voragine, Northeast and Bocca Nuova at Mount Etna, in an attempt to estimate compositions of the source volcanic gases. The estimated CO2/SO2 and H2O/CO2 ratios of the volcanic gases show a large variation ranging from 0.6 to 30 and from 1 to 18, respectively. This variability overlaps with the compositional range of dissolved volatiles in melt inclusions and their coexisting bubbles in a magma chamber and can be caused by the low-pressure degassing of a magma with variable bubble content ranging from 0.3 to 15 wt.%. The variable bubble content in the magma is…
Overview of the magnetic properties experiments on the Mars Explorations Rovers
2009
[1] The Mars Exploration Rovers have accumulated airborne dust on different types of permanent magnets. Images of these magnets document the dynamics of dust capture and removal over time. The strongly magnetic subset of airborne dust appears dark brown to black in Panoramic Camera (Pancam) images, while the weakly magnetic one is bright red. Images returned by the Microscopic Imager reveal the formation of magnetic chains diagnostic of magnetite-rich grains with substantial magnetization (>8 Am2 kg−1). On the basis of Mossbauer spectra the dust contains magnetite, olivine, pyroxene, and nanophase oxides in varying proportions, depending on wind regime and landing site. The dust contains a …
A numerical study of atmospheric signals in the Earth-ionosphere electromagnetic cavity with the Transmission Line Matrix method
2006
[1] The effect of the Earth-ionosphere electromagnetic cavity on the spectrum of an atmospheric signal generated by a broadband electrical current source is analyzed numerically by means of the Transmission Line Matrix (TLM) method. Two new TLM meshes are developed, one with transmission lines connected in parallel and the other with connections in series. The equations describing propagation through these parallel or series meshes are equivalent to the Maxwell equations for TEr or TMr modes in the spherical Earth-ionosphere cavity, respectively. The numerical algorithm obtains Schumann resonance frequencies very close to the experimental ones, confirming that this methodology is a valid nu…
Crustal dynamics of Mount Vesuvius from 1998 to 2005: Effects on seismicity and fluid circulation
2008
[1] This paper presents the results of hydrogeochemical and seismological studies carried out at Mount Vesuvius during the period June 1998 to December 2005. Hydrogeochemical data show the occurrence of slowly varying long-term variations in the total dissolved salts and bicarbonate contents of the groundwaters, accompanied by a general decline in water temperatures. The temporal distributions of air temperature and rainfall in the Vesuvius area suggest that these variations do not depend on changes in the hydrological regime. The changes in the geochemical parameters are accompanied by slight variations in both the seismicity rate and energy release. A further relationship between seismic …
Apparent absorption of solar spectral irradiance in heterogeneous ice clouds
2010
[1] Coordinated flight legs of two aircraft above and below extended ice clouds played an important role in the Tropical Composition, Cloud and Climate Coupling Experiment (Costa Rica, 2007). The Solar Spectral Flux Radiometer measured up- and downward irradiance on the high-altitude (ER-2) and the low-altitude (DC-8) aircraft, which allowed deriving apparent absorption on a point-by-point basis along the flight track. Apparent absorption is the vertical divergence of irradiance, calculated from the difference of net flux at the top and bottom of a cloud. While this is the only practical method of deriving absorption from aircraft radiation measurements, it differs from true absorption when…
CO2flux measurements in volcanic areas using the dynamic concentration method: Influence of soil permeability
2006
[1] In order to evaluate the influence of soil permeability on soil CO2 flux measurements performed with the dynamic concentration method, several tests were carried out using soils characterized by different permeability values and flow rates. A special device was assembled in the laboratory to create a one-dimensional gas flow through a soil of known permeability. Using the advective-diffusion theory, a physical model to predict soil concentration gradients was also developed. The calculated values of CO2 concentrations at different depths were compared with those measured during the tests and a good agreement was found. Four soils with different gas permeability (3.6 × 10−2 to 1.23 × 102…
Aerosol closure study by lidar, sun photometry, and airborne optical counters during DAMOCLES field campaign at El Arenosillo sounding station, Spain
2011
We present a comparison of aerosol properties derived from in situ and remote sensing instruments during DAMOCLES campaign, aimed at investigating the equivalence between the instrumentation and methodologies employed by several Spanish groups to study atmospheric aerosols at a regional background site. The complete set of instruments available during this closure experiment allowed collecting a valuable high-resolution aerosol measurement data set. The data set was augmented with airborne in situ measurements carried out in order to characterize aerosol particles during the midday of 29 June 2006. This work is focused on aerosol measurements using different techniques of high-quality instr…