137 research outputs found
Dust source activation frequency dataset
No full textThe data set contains information on the frequency of dust emission events, named dust source activation (DSA), on a regular longitude-latitude grid of 1°x1° resolution. The frequency is defined as number of observed DSA during the period March 2006 to February 2010.
Dust source activation events are inferred from 15-minute MSG SEVIRI IR dust index images as described in Schepanski et al. (2007, 2009) by back-tracing dust plumes to their place of origin.
As discussed in Schepanski et al. (2007, 2009, 2012), the DSA data provides information on the location of dust sources and their relevance.Schepanski, K., I. Tegen, B. Laurent, B. Heinold, and A. Macke (2007), A new Saharan dust source activation frequency map derived from MSG-SEVIRI IR-channels, Geophys. Res. Lett., 34, L18803, doi:10.1029/2007GL030168.
Schepanski, K., I. Tegen, M. C. Todd, B. Heinold, G. Bönisch, B. Laurent, and A. Macke (2009), Meteorological processes forcing Saharan dust emission inferred from MSG-SEVIRI observations of subdaily dust source activation and numerical models, J. Geophys. Res., 114, D10201, doi:10.1029/2008JD010325.
Schepanski, K., I. Tegen, and A. Macke (2012) Comparison of satellite based observations of Saharan dust source areas, Rem. Sens. Environm., 123, 90-97, doi:10.1016/j.rse.2012.03.019
The dust emission potential of agricultural-like fires—theoretical estimates from two conceptually different dust emission parameterizations
No full textAgricultural fires affecting grass-, crop- and shrublands represent a major, mainly anthropogenically driven disturbance of many ecosystems. In addition to emissions of carbonaceous aerosol, they were found to inject also mineral dust particles into the atmosphere. The fires can significantly modulate the near-surface wind patterns so that conditions suitable for dust emission occur. However, the exact emission mechanism has not been investigated so far, but is inevitable for the understanding of its impacts on the Earth system. Here, we test two dust emission parameterizations representing saltation bombardment (SALT) and direct aerodynamic dust entrainment by (convective) turbulence (convective turbulent dust emission, CTDE) in the context of fire-modulated wind patterns using large-eddy simulation with an idealized setup to represent typical agricultural fire settings. Favorable aerodynamic preconditions for the initialization of both emission processes are found, however, with sometimes significant differences in dust emission flux depending on specific wind and fire properties. The strong fire-induced modulations of the instantaneous momentum flux suggest that CTDE can be a very potent emission process in the fire vicinity. Nevertheless, fire impacts on the friction velocity can be significant too, so that dust emission through SALT is facilitated as well. Ultimately, the specific aerodynamic conditions within pyro-convectively modulated wind patterns require the development of a parameterization that can describe these unique fire-related dust emissions and their influencing factors properly. This will finally allow for considering fire-induced dust emissions in aerosol-atmosphere models and an investigation of its atmospheric impacts such as on the radiation budget.R. Wagner and K. Schepanski thank the German Research Foundation (Deutsche Forschungsgemeinschaft, DFG) for funding the project SCHE 1678/5–1. M. Klose has received funding from the European Union's Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No. 789630 and from the Helmholtz Association's Initiative and Networking Fund (grant agreement no. VH-NG-1533). The authors acknowledge the Center for Information Services and High performance Computing (ZIH) of the Technische Universität Dresden (TU Dresden) for providing computing capacity. The authors are grateful to the three anonymous reviewers for their valuable comments and suggestions that helped to improved the quality of the paper.Peer ReviewedPostprint (published version
North African mineral dust sources: new insights from a combined analysis based on 3D dust aerosol distributions, surface winds and ancillary soil parameters
No full textMineral dust aerosol is a key player in the climate system. Determining dust sources and the spatio-temporal variability of dust emission fluxes is essential for estimating the impact of dust on the atmospheric radiation budget, cloud and precipitation formation processes, the bio-productivity and, ultimately, the carbon cycle. Although much effort has been put into determining dust sources from satellite observations, geo-locating active dust sources is still challenging and uncertainties in space and time are evident. One major source of uncertainty is the lack of clear differentiation between near-source dust aerosol and transported dust aerosol. In order to reduce this uncertainty, we use 3D information on the distribution of dust aerosol suspended in the atmosphere calculated from spectral measurements obtained by the Infrared Atmospheric Sounding Interferometer (IASI) by using the Mineral Aerosols Profiling from Infrared Radiance (MAPIR) algorithm. In addition to standard dust products from satellite observations, which provide 2D information on the horizontal distribution of dust, MAPIR allows for the retrieval of additional information on the vertical distribution of dust plumes. This ultimately enables us to separate between near-source and transported dust plumes. Combined with information on near-surface wind speed and surface properties, low-altitude dust plumes can be assigned to dust emission events and low-altitude transport regimes can be excluded. Consequently, this technique will reduce the uncertainty in automatically geo-locating active dust sources. The findings of our study illustrate the spatio-temporal distribution of North African dust sources based on 9 years of data, allowing for the observation of a full seasonal cycle of dust emissions, differentiating morning and afternoon/evening emissions and providing a first glance at long-term changes. In addition, we compare the results of this new method to the results from Schepanski et al. (2012), who manually identified dust sources from Spinning Enhanced Visible and InfraRed Imager (SEVIRI) red–green–blue (RGB) images. The comparison illustrates that each method has its strengths and weaknesses that must be taken into account when using the results. This study is of particular importance for understanding future environmental changes due to a changing climate
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North African mineral dust sources: New insights from a combined analysis based on 3D dust aerosol distributions, surface winds and ancillary soil parameters
No full textMineral dust aerosol is a key player in the climate system. Determining dust sources and the spatio-temporal variability of dust emission fluxes is essential for estimating the impact of dust on the atmospheric radiation budget, cloud and precipitation formation processes, the bio-productivity and, ultimately, the carbon cycle. Although much effort has been put into determining dust sources from satellite observations, geo-locating active dust sources is still challenging and uncertainties in space and time are evident. One major source of uncertainty is the lack of clear differentiation between near-source dust aerosol and transported dust aerosol. In order to reduce this uncertainty, we use 3D information on the distribution of dust aerosol suspended in the atmosphere calculated from spectral measurements obtained by the Infrared Atmospheric Sounding Interferometer (IASI) by using the Mineral Aerosols Profiling from Infrared Radiance (MAPIR) algorithm. In addition to standard dust products from satellite observations, which provide 2D information on the horizontal distribution of dust, MAPIR allows for the retrieval of additional information on the vertical distribution of dust plumes. This ultimately enables us to separate between near-source and transported dust plumes. Combined with information on near-surface wind speed and surface properties, low-altitude dust plumes can be assigned to dust emission events and low-altitude transport regimes can be excluded. Consequently, this technique will reduce the uncertainty in automatically geo-locating active dust sources. The findings of our study illustrate the spatio-temporal distribution of North African dust sources based on 9 years of data, allowing for the observation of a full seasonal cycle of dust emissions, differentiating morning and afternoon/evening emissions and providing a first glance at long-term changes. In addition, we compare the results of this new method to the results from Schepanski et al. (2012), who manually identified dust sources from Spinning Enhanced Visible and InfraRed Imager (SEVIRI) red-green-blue (RGB) images. The comparison illustrates that each method has its strengths and weaknesses that must be taken into account when using the results. This study is of particular importance for understanding future environmental changes due to a changing climate. © Author(s) 202
Понятие “социальный круг” в истории социологии
No full textThe term “social circle” is used primarily as an auxiliary term that helps to characterize
a social structure, designate the belonging of individuals to a certain social group or
another social formation. The one way to prove this term as sociological notion is
historical sociological analysis of social circle as a scientific term and a notion.
The main approaches in the history of sociology to the notion of “social circle” are
under analysis in paper. The author examines theoretical interpretations of this notion
by classics (F. Tönnies, G.Simmel) and neoclassics (P.Blau, J. Schepanski, analysts of
network analyses). The article gives a summary and generalization of their ideas about
social circle
Soudano-Saharan depressions and their importance for precipitation and dust: a new perspective on a classical synoptic concept
No full textAccording to a classical synoptic concept, Soudano-Saharan depressions (SSDs) are surface lows that track westward over tropical West Africa, curve anticyclonically across the Sahara and may then transform into eastward-moving Mediterranean cyclones. Occurrence frequency and track location undergo a marked seasonal cycle. Interactions between troughs in the upper-level westerlies and mid-level African easterly waves have been suggested as a mechanism for their formation. SSDs have been reported to be associated with dust-storms and precipitation over northern Africa. This paper presents the first-ever systematic investigation of SSDs using re-analysis and satellite data. Depressions are identified and tracked objectively based on closed contours in 0000 UTC fields of 925 hPa geopotential height from the European Centre for Medium-Range Weather Forecasts ERA-Interim re-analysis (1989-2008). To classify as potential SSDs, tracks must: (i) start to the south of 20°N; (ii) intersect 15°-30°N, 10°W-30°E; (iii) cover a meridional distance of at least 10° latitude; and (iv) have a minimum lifetime of 24 hours. Even with a relatively low threshold of 4 gpm, only 50 potential SSDs are found (annual average 2.5, monthly range 0-6). Lagrangian and Eulerian composite analyses reveal that the identified systems: (i) are mostly shallow lee troughs of the central Saharan and Atlas Mountains during the warm season without a well-defined cyclonic wind field; (ii) do not show the seasonal track variation described in the literature; (iii) mostly occur in association with high-pressure anomalies over the Mediterranean Sea; and (iv) are not associated with significant increases in dustiness and precipitation. These results strongly suggest that the disturbances described as SSDs do not manifest themselves as traceable low-level depressions, calling for a fundamental revision of the classical concept in the literature
Понятие “социальный круг” в истории социологии
No full textThe term “social circle” is used primarily as an auxiliary term that helps to characterize
a social structure, designate the belonging of individuals to a certain social group or
another social formation. The one way to prove this term as sociological notion is
historical sociological analysis of social circle as a scientific term and a notion.
The main approaches in the history of sociology to the notion of “social circle” are
under analysis in paper. The author examines theoretical interpretations of this notion
by classics (F. Tönnies, G.Simmel) and neoclassics (P.Blau, J. Schepanski, analysts of
network analyses). The article gives a summary and generalization of their ideas about
social circle
Soudano-Saharan Depressions and their importance for precipitation and dust: A new perspective on a classical synoptic concept
No full textSaharan dust transport and deposition towards the tropical northern Atlantic
No full textWe present a study of Saharan dust export towards the tropical North Atlantic using the regional dust emission, transport and deposition model LM-MUSCAT. Horizontal and vertical distribution of dust optical thickness, concentration, and dry and wet deposition rates are used to describe seasonality of dust export and deposition towards the eastern Atlantic for three typical months in different seasons. Deposition rates strongly depend on the vertical dust distribution, which differs with seasons. Furthermore the contribution of dust originating from the Bodélé Depression to Saharan dust over the Atlantic is investigated. A maximum contribution of Bodélé dust transported towards the Cape Verde Islands is evident in winter when the Bodélé source area is most active and dominant with regard to activation frequency and dust emission. Limitations of using satellite retrievals to estimate dust deposition are highlighted
Soudano-Saharan Depressions and their importance for precipitation and dust - a new perspective on a classical synoptic concept
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