198 research outputs found
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Optical and microphysical properties of smoke over Cape Verde inferred from multiwavelength lidar measurements
Lidar measurements of mixed dust/smoke plumes over the tropical Atlantic ocean were carried out during the winter
campaign of SAMUM-2 at Cape Verde. Profiles of backscatter and extinction coefficients, lidar ratios, and Ångstr¨om
exponents related to pure biomass-burning aerosol from southern West Africa were extracted from these observations.
Furthermore, these findings were used as input for an inversion algorithm to retrieve microphysical properties of pure
smoke. Seven measurement days were found suitable for the procedure of aerosol-type separation and successive
inversion of optical data that describe biomass-burning smoke. We inferred high smoke lidar ratios of 87 ± 17 sr at
355 nm and 79 ± 17 sr at 532 nm. Smoke lidar ratios and Ångstr¨om exponents are higher compared to the ones for the
dust/smoke mixture. These numbers indicate higher absorption and smaller sizes for pure smoke particles compared
to the dust/smoke mixture. Inversion of the smoke data set results in mean effective radii of 0.22 ± 0.08 μm with
individual results varying between 0.10 and 0.36 μm. The single-scattering albedo for pure biomass-burning smoke
was found to vary between 0.63 and 0.89 with a very low mean value of 0.75 ± 0.07. This is in good agreement with
findings of airborne in situ measurements which showed values of 0.77 ± 0.03. Effective radii from the inversion were
similar to the ones found for the fine mode of the in situ size distributions
Word Recognition Memory in Adults with Attention-Deficit/Hyperactivity Disorder as Reflected by Event-Related Potentials
Objective: Attention-deficit/hyperactivity disorder (ADHD) is increasingly diagnosed in adults. In this study we address the question whether there are impairments in recognition memory. Methods: In the present study 13 adults diagnosed with ADHD according to DSM-IV and 13 healthy controls were examined with respect to event-related potentials (ERPs) in a visual continuous word recognition paradigm to gain information about recognition memory effects in these patients. Results: The amplitude of one attention-related ERP component, the N1, was significantly increased for the ADHD adults compared with the healthy controls in the occipital electrodes. The ERPs for the second presentation were significantly more positive than the ERPs for the first presentation. This effect did not significantly differ between groups. Conclusion: Neuronal activity related to an early attentional mechanism appears to be enhanced in ADHD patients. Concerning the early or the late part of the old/new effect ADHD patients show no difference which suggests that there are no differences with respect to recollection and familiarity-based recognition processes
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Vertical profiling of Saharan dust with Raman lidars and airborne HSRL in southern Morocco during SAMUM
Three ground-based Raman lidars and an airborne high-spectral-resolution lidar (HSRL) were operated duringSAMUM 2006 in southern Morocco to measure height profiles of the volume extinction coefficient, the extinction-to-backscatter ratio and the depolarization ratio of dust particles in the Saharan dust layer at several wavelengths. Aerosol Robotic Network (AERONET) Sun photometer observations and radiosoundings of meteorological parameters complemented the ground-based activities at the SAMUM station of Ouarzazate. Four case studies are presented. Two case studies deal with the comparison of observations of the three ground-based lidars during a heavy dust outbreak and of the ground-based lidars with the airborne lidar. Two further cases show profile observations during satellite overpasses on 19 May and 4 June 2006. The height resolved statistical analysis reveals that the dust layer top typically reaches 4–6 km height above sea level (a.s.l.), sometimes even 7 km a.s.l.. Usually, a vertically inhomogeneous dust plume with internal dust layers was observed in the morning before the evolution of the boundary layer started. The Saharan dust layer was well mixed in the early evening. The 500 nm dust optical depth ranged from 0.2–0.8 at the field site south of the High Atlas mountains, Ångström exponents derived from photometer and lidar data were between 0–0.4. The volume extinction coefficients (355, 532 nm) varied from 30–300Mm−1 with a mean value of 100Mm−1 in the lowest 4 km a.s.l.. On average, extinction-to-backscatter ratios of 53–55 sr (±7–13 sr) were obtained at 355, 532 and 1064 nm
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Regional modelling of Saharan dust and biomass-burning smoke, Part I: Model description and evaluation
The spatio-temporal evolution of the Saharan dust and biomass-burning plume during the SAMUM-2 field campaign
in January and February 2008 is simulated at 28 km horizontal resolution with the regional model-system COSMOMUSCAT.
The model performance is thoroughly tested using routine ground-based and space-borne remote sensing
and local field measurements. Good agreement with the observations is found in many cases regarding transport
patterns, aerosol optical thicknesses and the ratio of dust to smoke aerosol. The model also captures major features
of the complex aerosol layering. Nevertheless, discrepancies in the modelled aerosol distribution occur, which are
analysed in detail. The dry synoptic dynamics controlling dust uplift and transport during the dry season are well
described by the model, but surface wind peaks associated with the breakdown of nocturnal low-level jets are not
always reproduced. Thus, a strong dust outbreak is underestimated. While dust emission modelling is a priori more
challenging, since strength and placement of dust sources depend on on-line computed winds, considerable inaccuracies
also arise in observation-based estimates of biomass-burning emissions. They are caused by cloud and spatial errors of
satellite fire products and uncertainties in fire emission parameters, and can lead to unrealistic model results of smoke
transport
Are earth sciences lagging behind in data integration methodologies?
This article reflects discussions German and South
African Earth scientists, statisticians and risk analysts
had on occasion of two bilateral workshops on Data
Integration Technologies for Earth System Modelling
and Resource Management. The workshops were
held in October 2012 at Leipzig, Germany, and April
2013 at Pretoria, South Africa, and were attended by
about 70 researchers, practitioners and data managers
of both countries. Both events were arranged as
part of the South African-German Year of Science
2012/2013. The South African National Research
Foundation (NRF, UID 81579) has supported the two
workshops as part of the South African--German Year
of Science activities 2012/2013 established by the German Federal Ministry of Education and Research
and the South African Department of Science and
Technology.http://link.springer.com/journal/12665hb201
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