1,720,972 research outputs found
High resolution measurement of aerosol equivalent scale heigth over wide range
No full textAerosol vertical optical depth (AOD) and horizontal extinction coefficient (AEC) have
been measured with multiwavelength photometers at University of Granada, during the
period 14
th
-18
th
July 2006. The AOD τ
aer
has been measured by using an Avantes
USB2000 high grating spectrometer (440–900 nm, 1.5 nm resolution); at the same
moment a FieldSpec has been used to measure Horizontal Aerosol Extinction
Coefficient (AEC) σ
aer
in the range 400-700 nm , with a resolution of 1 nm. Both AOD
and AEC were used to obtain an equivalent Ae rosol scale height at different wavelength
in the range 440-700 nm , according to Mie scattering theory
Aerosol optical properties in Mediterranean basin underSaharan dust outbreaks
No full textFour measurement campaigns held in three different sites of the Mediterranean
basin and in different years revealed the intrusion of mineral dust coming from North
Africa, as confirmed even by the HYSPLIT back-trajectories analysis. Two of the sites
are located in South Italy, the third one is in South Spain.. One data-set was obtained by
a Monolight spectrometer (400 nm – 800 nm, resolution 3 nm), the other by means of
an Avantes USB2000 spectrometer (400 nm – 900 nm, resolution 1.5 nm). A fitting
procedure and a non-parametric inversion t echnique were applied to the measured
AODs to retrieve, respectively, the Ǻngström parameters α and β and the Aerosol Size
Distributions. Each site is characterised by different size distributions (bi-modal and
Junge functions) but, independently from thes e functions, all the measurements affected
by Saharan dust showed higher particles density in the radii range 0.43 μm ≤ r ≤ 3.0 μm.
The second result is the strong correlation between α and ln( β ) for dust data points
obtained in all sites, suggesting that mineral particles properties predominate over the
background ones. Finally, Aerosol Size Distributions have been simulated, modifying
their log-normal parameters and fixing, time by time, the refractive index values, to
reproduce the experimental α vs. ln( β ) behaviour. In this way, an “equivalent refractive
index” common to the dust data has been retrieved
Effects of Saharan Dust Advection on Atmospheric Aerosol Properties in the West-Mediterranean Area
Full text linkEight measurement campaigns for the characterization of atmospheric aerosol properties were conducted from 2001 until 2008 at five sites located in the Western Mediterranean basin. Radiometric measurements were used to obtain Aerosol Optical Depth, Ångström parameters, and aerosol size distributions, allowing differentiation of background conditions from anthropogenic, marine, or Saharan dust aerosol advection. The analysis was focused on the study of optical and physical properties variation of atmospheric aerosols under Saharan outbreaks. Dust-affected data were analysed all together, independently from the measurements site, thus allowing the highlighting of similarities and differences among them. The scatter-plot Ångström exponent versus AOD at 780 nm shows a correlation among all dust data, while an overlapping region with no-dust data reveals the simultaneous presence of mineral, anthropogenic, and marine particles. Daily averaged volume size distributions can be unimodal or bimodal functions and one three-modal distribution, with a coarse mode generally prevailing. Finally, considering the ratio of small/large particles / and plotting the corresponding histogram for all dust data, a sharp frequency distribution is obtained with 89% of data in the range 5–65, while 89% of no-dust data extend from 5 to 135, in spite of different sources, pathways, and arrival sites
Radiometric performances of the Fourier transform spectrometer for the Radiation Explorer in the Far-Infrared (REFIR) space mission
No full textAerosol optical properties variation on different mountain sites in Italy
No full textDirect solar irradiance and IR atmospheric radiance have been measured during different measurements campaigns, conducted in three mountain sites in Italy, far from anthropogenic sources. Direct solar irradiance has been measured by a high resolution (1.5 nm) AVANTES radiometer, working in the spectral range 400 nm-900 nm, while down welling IR sky radiance measurements has been measured by an MR100 BOMEM Fourier Transform Spectrometer covering the spectral ranges 500 cm-1-5000 cm-1 and 1 cm-1 of resolution. At least two Radiosonde launches per day furnished temperature and water vapour profiles. The instruments were located on a mobile laboratory, specifically projected to host them. The parameters obtained from direct solar irradiance are Aerosol Optical Depth, Angstrom parameters and Aerosol Size Distributions retrieval, while from IR data water vapour and temperature profiles have been retrieved. Different orographic characteristics and different air-masses circulation on the measurement sites influenced Aerosol Optical Depth values and variation. Infrared radiances inversion allows the water vapour content retrieval and a correlation between aerosol effective radii and water vapour content has been looked for
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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