Search results for "Geophysic"
showing 10 items of 2684 documents
Intercomparison and analyses of the climatology of the West African Monsoon in the West African Monsoon Modeling and Evaluation project (WAMME) first…
2010
International audience; This paper briefly presents the West African Monsoon (WAM) Modeling and Evaluation Project (WAMME) and evaluates WAMME general circulation models' (GCM) performances in simulating variability of WAM precipitation, surface temperature, and major circulation features at seasonal and intraseasonal scales in the first WAMME experiment. The analyses indicate that models with specified sea surface temperature generally have reasonable simulations of the pattern of spatial distribution of WAM seasonal mean precipitation and surface temperature as well as the averaged zonal wind in latitude-height cross-section and low level circulation. But there are large differences among mo…
Aerosol layers from the 2008 eruptions of Mount Okmok and Mount Kasatochi: In situ upper troposphere and lower stratosphere measurements of sulfate a…
2010
In 2008 Mount Okmok and Mount Kasatochi started erupting on 12 July and 7 August, respectively, in the Aleutians, depositing emissions of trace gases and aerosols as high as 15.2 km into the atmosphere. During an aircraft campaign, conducted over Europe in between 27 October and 2 November 2008, the volcanic aerosol was measured by an Aerodyne aerosol mass spectrometer, capable of particle chemical composition measurements covering a size diameter range between 40 nm and 1 mm. In the volcanic aerosol layer enhanced submicron particulate sulfate concentrations of up to 2.0 mg mâÂÂ3 standard temperature and pressure (STP) were observed between 8 and 12 km altitude, while background values …
Electrical conductivity of magma in the course of crystallization controlled by their residual liquid composition.
2005
International audience; The electrical conductivity of a magma in the course of crystallization was experimentally investigated in the temperature range of 1350–1018°C. Large samples of basaltic composition with a homogeneous crystal content were synthesized in a gas mixing furnace at 1 atm pressure. The samples were analyzed by electron microprobe. The relative proportions of the phases as a function of temperature were determined. Depending on temperature, the phase assemblies included quenched silicate liquid, ±plagioclase, ±pyroxene, ±Fe-Ti oxides. The crystal content varied from 0 to 80 wt %. In response to partial crystallization, the residual liquid changed composition from basalt, t…
Influx of African biomass burning aerosol during the Amazonian dry season through layered transatlantic transport of black carbon-rich smoke
2020
Black carbon (BC) aerosols influence the Earth's atmosphere and climate, but their microphysical properties, spatiotemporal distribution, and long-range transport are not well constrained. This study presents airborne observations of the transatlantic transport of BC-rich African biomass burning (BB) smoke into the Amazon Basin using a Single Particle Soot Photometer (SP2) as well as several complementary techniques. We base our results on observations of aerosols and trace gases off the Brazilian coast onboard the HALO (High Altitude and LOng range) research aircraft during the ACRIDICON-CHUVA campaign in September 2014. During flight AC19 over land and ocean at the northeastern coastline …
Observationally Weak TGFs in the RHESSI Data
2019
Abstract Terrestrial gamma ray flashes (TGFs) are sub‐millisecond bursts of high energetic gamma radiation associated with intracloud flashes in thunderstorms. In this paper we use the simultaneity of lightning detections by World Wide Lightning Location Network to find TGFs in the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) data that are too faint to be identified by standard search algorithms. A similar approach has been used in an earlier paper, but here we expand the data set to include all years of RHESSI + World Wide Lightning Location Network data and show that there is a population of observationally weak TGFs all the way down to 0.22 of the RHESSI detection thresh…
Anisotropic scaling of tectonic stylolites: A fossilized signature of the stress field?
2010
International audience; [1] Vertical stylolites are pressure solution features, which are considered to be caused by horizontal tectonic loading, with the largest principal compressive stress being (sub-) parallel to the Earth's surface. In the present study we analyze the roughness of such tectonic stylolites from two tectonic settings in southern Germany and northeastern Spain, aiming to investigate their scaling properties with respect to the stress during formation. High-resolution laser profilometry was carried out on opened stylolite surfaces of nine samples. These data sets were then analyzed using one-and two-dimensional Fourier power spectral approaches. We found that tectonic styl…
Observed versus simulated mountain waves over Scandinavia – improvement of vertical winds, energy and momentum fluxes by enhanced model resolut…
2017
Abstract. Two mountain wave events, which occurred over northern Scandinavia in December 2013 are analysed by means of airborne observations and global and mesoscale numerical simulations with horizontal mesh sizes of 16, 7.2, 2.4 and 0.8 km. During both events westerly cross-mountain flow induced upward-propagating mountain waves with different wave characteristics due to differing atmospheric background conditions. While wave breaking occurred at altitudes between 25 and 30 km during the first event due to weak stratospheric winds, waves propagated to altitudes above 30 km and interfacial waves formed in the troposphere at a stratospheric intrusion layer during the second event. Global an…
The Arctic Cloud Puzzle: Using ACLOUD/PASCAL Multiplatform Observations to Unravel the Role of Clouds and Aerosol Particles in Arctic Amplification
2019
A consortium of polar scientists combined observational forces in a field campaign of unprecedented complexity to uncover the secrets of clouds and their role in Arctic amplification. Two research aircraft, an icebreaker research vessel, an ice-floe camp including an instrumented tethered balloon, and a permanent ground-based measurement station were employed in this endeavour. Clouds play an important role in Arctic amplification. This term represents the recently observed enhanced warming of the Arctic relative to the global increase of near-surface air temperature. However, there are still important knowledge gaps regarding the interplay between Arctic clouds and aerosol particles, surfa…
A Laboratory Dust Generator Applying Vibration to Soil Sample: Mineralogical Study and Compositional Analyses
2020
International audience; A laboratory study was carried out using a vibrating system (SyGAVib) to produce aerosols from four soils collected in the central Tunisian region around Sfax. The aim of this device is to mimic dust emission by natural wind erosion. Using compositional analysis, the dust produced was compared to (i) dust generated in a wind tunnel by the same soils, (ii) fine sieved and (iii) original bulk soils, and (iv) naturally occurring aerosol samples collected in the same area. The relative quartz content strongly decreases from bulk to fine soils, and again from fine soils to both wind tunnel and vibration‐generated aerosols. Compositional data analysis (CoDA) clearly shows …
In-situ observations and modeling of small nitric acid-containing ice crystals
2007
Measurements in nascent ice forming regions are very rare and help understand cirrus cloud formation and the interactions of trace gases with ice crystals. A tenuous cirrus cloud has been probed with in-situ and remote sensing instruments onboard the high altitude research aircraft Geophysica M55 in the tropical upper troposphere. Besides microphysical and optical particle properties, water (H<sub>2</sub>O) and reactive nitrogen species (NO<sub>y</sub>) have been measured. In slightly ice supersaturated air between 14.2 and 14.9 km altitude, an unusually low ice water content of 0.031 mg m<sup>&minus;3</sup> and small ice crystals with mean radii of 5…