Search results for " dust"

Oxygen isotopes in single micrometer-sized quartz grains: tracing the source of Saharan dust over long-distance atmospheric transport

2002

Abstract Oxygen isotope compositions were measured by ion microprobe in individual micrometer-sized quartz grains extracted from one aerosol sample collected on the Cape Verde Islands and from four surface samples (three soils and one sediment) representing potential source regions of aerosols in Western and Central Africa (Morocco, Algeria, Niger, and Chad). A large range of δ18O values, from +6.2‰ to +39.3‰ is present within the aerosol quartz grains. The different size fractions of the quartz grains from the surface samples overlap nearly entirely this range but show significant differences in their δ18O distributions for the different size fractions of the grains (i.e., different modes,…

Magnetic susceptibility and heavy metal content in dust from the lime plant and the cement plant in Opole Voivodeship

2012

Magnetic Susceptibility and Heavy Metal Content in Dust From the Lime Plant and the Cement Plant in Opole Voivodeship Until now, dust arising from lime manufacture has been considered harmless to the environment so it has been investigated marginally from the standpoint of environmental protection, especially when it came to magnetic properties and heavy metal content. The aim of the research was filling the gap in this area. The research comprised measurements of magnetic susceptibility, the content of heavy metals, reaction (pH) and specific conductivity of lime dust and also raw material and fuel used for lime production. The samples were taken from one of the lime plants located in Opol…

Study of polychlorinated biphenyls in street dust by supercritical fluid extraction-gas chromatography/mass spectrometry

1996

Street dust samples have been collected from highways, urban streets, a gasoline station, a pedestrian tunnel, and railway stations in some German cities. Nine polychlorinated biphenyls (PCBs from tri- to heptachlorobiphenyls) were quantitatively extracted by supercritical fluid extraction with CO2 at 200 bar and 40°C and analyzed by gas chromatography/mass spectrometry. The highest PCB loads (sum of the nine studied PCBs) of ca. 1 to 4 μg/g have been found in the samples from motorway A60 near Mainz, while in almost all other samples PCBs could be detected at only ca. 0.1 to 1 μg/g. At three sampling sites, a winter maximum of the PCB concentrations has been found.

Development of a New Sunphotometer and Establishment of a Network Across Africa for the Investigation of the Transport of Sahara Dust

1982

The matter of this project is the investigation of the large scale south transport of Saharan dust originated by critical weather conditions such as sandstorm and dustvi/ind. A new sensitive sunphoto-meter has been developed for this purpose. With ten instruments a network has been installed southerly of the Sahara across Africa. It is the aim to determine the main sources of the mineral dust and its further transport to the South.

Vertical profiling of convective dust plumes in southern Morocco during SAMUM

2011

Lifting of dust particles by dust devils and convective plumes may significantly contribute to the global mineral dust budget. During the Saharan Mineral Dust Experiment (SAMUM) in May–June 2006 vertical profiling of dusty plumes was performed for the first time. Polarization lidar observations taken at Ouarzazate (30.9°N, 6.9°W, 1133 m height above sea level) are analyzed. Two cases with typical and vigorous formation of convective plumes and statistical results of 5 d are discussed. The majority of observed convective plumes have diameters on order of 100–400 m. Most of the plumes (typically 50–95%) show top heights <1 km or 0.3DLH with the Saharan dust layer height DLH of typically 3–…

Small ice particles at slightly supercooled temperatures in tropical maritime convection

2020

In this paper we show that the origin of the ice phase in tropical cumulus clouds over the sea may occur by primary ice nucleation of small crystals at temperatures just between 0 and −5 ∘C. This was made possible through use of a holographic instrument able to image cloud particles at very high resolution and small size (6 µm). The environment in which the observations were conducted was notable for the presence of desert dust advected over the ocean from the Sahara. However, there is no laboratory evidence to suggest that these dust particles can act as ice nuclei at temperatures warmer than about −10 ∘C, the zone in which the first ice was observed in these clouds. T…

2017

Abstract. We present a sensitivity study on transatlantic dust transport, a process which has many implications for the atmosphere, the ocean and the climate. We investigate the impact of key processes that control the dust outflow, i.e., the emission flux, convection schemes and the chemical aging of mineral dust, by using the EMAC model following Abdelkader et al. (2015). To characterize the dust outflow over the Atlantic Ocean, we distinguish two geographic zones: (i) dust interactions within the Intertropical Convergence Zone (ITCZ), or the dust–ITCZ interaction zone (DIZ), and (ii) the adjacent dust transport over the Atlantic Ocean (DTA) zone. In the latter zone, the dust loading show…

High‐resolution simulations of convective cold pools over the northwestern Sahara

2009

[1] Cooling by evaporation of convective precipitation in the deep and dry subcloud layer over desert regions can generate intense downdrafts and long-lived and extensive atmospheric density currents. The strong gusts at their leading edges can cause so-called haboob dust storms. Despite their importance for the dust cycle, the ability of state-of-the-art numerical weather prediction models to realistically simulate the associated convective cold pools has been investigated very little to date. During the first field campaign of the Saharan Mineral Dust Experiment in southern Morocco in May/June 2006, several density currents were observed. They were triggered by deep moist convection over …

Dust mobilization due to density currents in the Atlas region: Observations from the Saharan Mineral Dust Experiment 2006 field campaign

2007

[1] Evaporation of precipitation is a ubiquitous feature of dry and hot desert environments. The resulting cooling often generates density currents with strong turbulent winds along their leading edges, which can mobilize large amounts of dust. Mountains support this process by triggering convection, by downslope acceleration of the cool air, and by fostering the accumulation of fine-grained sediments along their foothills through the action of water. For the Sahara, the world's largest dust source, this mechanism has been little studied because of the lack of sufficiently high resolution observational data. The present study demonstrates the frequent occurrence of density currents along th…

The influence of absorbed solar radiation by Saharan dust on hurricane genesis

2015

To date, the radiative impact of dust and the Sahar an air layer (SAL) on North Atlantic hurricane activity is not yet known. According to previous studies, dust stabilizes the atmosphere due to absorption of solar radiation but thus shifts convection to regions more conducive for hurricane genesis. Here we analyze differences in hurricane genesis and frequency from ensemble sensitivity simulations with radiatively active and inactive dust in the aerosol-climate model ECHAM6-HAM. We investigate dust burden and other hurricane-related variables and determine their influence on disturbances which develop into hurricanes (developing disturbances, DDs) and those which do not (nondeveloping dist…