1,721,006 research outputs found
Multiparameter Raman Lidar Measurements for the Characterization of a Dry Stratospheric Intrusion Event
No full textThe UV Raman lidar system (BASIL), operational at University of Basilicata (Potenza-Italy) and capable to perform high-resolution and accurate measurements of atmospheric temperature and water vapour based on the application of the rotational and vibrational Raman lidar techniques in the UV, was recently involved in the LAUNCH 2005 experiment (International Lindenberg campaign for assessment of humidity and cloud profiling systems and its impact on high-resolution modelling) held from 12 September to 31 October 2005. A thorough description of technical characteristics, measurements capabilities and performances of BASIL is given in the paper. Measurements were continuously run between 1 and 3 October 2005, covering a dry stratospheric intrusion episode associated with a tropopause folding event. The measurements in this paper represent the first simultaneous Raman Lidar measurements of atmospheric temperature and water vapour mixing ratio, and consequently relative humidity, reported for an extensive observation period (32 hours).
The use of water vapour to trace intruded stratospheric air allows to clearly identify a dry structure (approx. 1 km thick) originated in the stratosphere and descending in the free troposphere down to ~ 3 km. A similar feature is present in the temperature field, with lower temperature values detected within the dry air tongue. Relative humidity measurements reveal values as small as 0.5-1 % within the intruded air. The stratospheric origin of the observed dry layer has been verified by the application of a Lagrangian trajectory model. The subsidence of the intruding heavy dry air may be responsible for the gravity wave activity observed beneath the dry layer.
Lidar measurements have been compared with the output of both the PSU/NCAR Mesoscale Model (MM5) and the European Center for Medium range Weather Forecasting (ECMWF) global model. Comparisons in term of water vapour reveal the capability of MM5 to reproduce the dynamical structures associated with the stratospheric intrusion episode and simulate the deep penetration into the troposphere of the dry intruded layer. Moreover, lidar measurements of potential temperature are compared with MM5 output, while potential vorticity from both ECMWF and MM5 is compared with estimates obtained combining MM5 model vorticity and lidar measurements of potential temperature
Rotational Raman Lidar measurements for the characterization of stratosphere-troposphere exchange mechanisms
No full textA UV Raman lidar system (BASIL) is operational at DIFA-Univ. of Basilicata (Potenza-Italy). The system
was recently involved in LAUNCH 2005 the International Lindenberg campaign for assessment of
humidity and cloud profiling systems and its impact on high-resolution modelling - held from 12
September to 31 October 2005. During this period BASIL collected approx. 250 hours of measurements
distributed over 13 Intensive Observation Periods (IOPs) and 25 days. One specific IOP was
continuously run between 1-3 October 2005, covering a dry stratospheric intrusion episode associated
with a tropopause folding event and the subsequent onset of perturbed weather conditions that leaded
to the development of clouds and precipitations. Tropopause folds are the dominant and most efficient
mechanism of stratosphere-troposphere exchange (STE) in the middle latitudes [1]. Intruding
stratospheric air forms filamentary features in ozone and water vapour profiles [2]. The use of water
vapour to trace intruded stratospheric air allows to clearly identify a dry structure (approx. 1 km thick)
originated in the stratosphere and descending in the free troposphere down to ~ 3 km. A similar feature
is present in the temperature field, with lower temperature values observed within the dry air tongue.
Relative humidity measurements reveal values as small as 0.5-1 % within the intruded air. The
stratospheric origin of the observed dry layer has been verified by the application of a Lagrangian
trajectory model. The subsidence of the intruding heavy dry air is most probably responsible for the
gravity wave activity observed beneath the dry layer. Lidar measurements have been compared with
forecasts from a MM5 mesoscale model. Comparisons in term of water vapour reveal the capability of
the model to forecast the deep penetration into the troposphere of the dry intruded layer. Global and
mesoscale forecasts of potential temperature and potential vorticity are compared with those estimated
from lidar measurements. Comparisons of lidar and model data will be discussed in detail at the
conference. References 1. Holton, J. R., et al., Stratosphere-troposphere exchange, Rev. Geophys., 33,
403439, 1995. 2. Appenzeller, C., and H. C. Davies, Structure of stratospheric intrusions into the
troposphere, Nature, 358, 570 572, 1992
UV Raman lidar measurements of relative humidity for the characterization of aerosol hygroscopicity and cloud microphysical properties
No full textA UV Raman lidar system (BASIL) is operational at DIFA-Univ. of Basilicata (Potenza-Italy). The major feature of
BASIL is its capability to perform high-resolution and accurate measurements of atmospheric temperature, both in
daytime and night-time, based on the application of the rotational Raman lidar technique in the UV [1]. Besides
temperature, BASIL is capable to provide measurements of particle backscatter at 355 and 532 nm, particle extinction at
355 nm, particle depolarization at 355 and water vapour mixing ratio. Relative humidity (RH) measurements are
obtained from simultaneous water vapour mixing ratio and temperature measurements. These parameters represents a
suitable ensemble of measurements for the study of meteorological processes.
Specific case studies are considered and discussed to assess RH lidar measurement capability in presence of aerosols and
clouds. Measurements of aerosol backscatter as a function of relative humidity are illustrated, highlighting the swelling
tendency of hygroscopic aerosol for large relative humidity values (in excess of 80 %). Relative humidity measurements
in the proximity and within cirrus clouds are also illustrated and discussed. Both ice super-saturation and undersaturation
conditions are found inside these clouds, but air is observed to be always under-saturated with respect to water.
The sublimation of the precipitating ice crystals in cirrus clouds is found to cause upper tropospheric humidification, and
lead to increased relative humidity values beneath the clouds
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
Clear and cloudy sky investigations using Raman lidar and airborne interferometric measures from the European AQUA Thermodynamic Experiment
No full textA dataset of ground, airborne and satellite data was measured during the comprehensive 2004
EAQUATE (European AQUA Thermodynamic Experiment) Italian campaign. We have used
ground based and airborne data to evaluate the consistency of Raman lidar temperature and
humidity profiles with NAST-I (The National Polar-orbiting Operational Environmental
Satellite System Airborne Sounder Testbed-Interferometer) spectral radiance measurements
in clear conditions, and the consistency of total cloud optical depth measured by the Raman
lidar with the same quantity retrieved from NAST-I measurements.
Lidar measurement of temperature and humidity profiles can resolve short time changes in
mixing ratio due to its high time resolution. Brightness temperature simulations of clear sky,
performed using lidar-derived profiles, are within 1 K difference with respect to data when
averages over 25 cm−1 and emission from layers below 7 km are considered. High spectral
resolution simulations agree with NAST-I measurements with a mean percentage difference
less than 0.5% in the whole ν2 water vapour band.
The simulations in cloudy conditions are based on crystal properties obtained assuming either an
appropriatemixture of crystal habits (that for the first time is tested against high spectral resolution
measurements) or pristine solid columns. Lidar-derived cloud base and top altitudes and lidar
temperature and humidity profiles are exploited, for the first time, as inputs in a recently developed
infrared cloud properties retrieval procedure. Total cloud optical depths, retrieved from 800 to
980 cm−1 NAST-I radiances, have values that,when converted to short-wave wavelengths, are in the
range 0.05–2.2 and agree with lidar measurements to within experimental errors. A closer
agreement is obtained with the mixture of habits. Simulated high resolution brightness
temperatures based on retrieved cloud parameters (optical depths and effective dimensions) are
compared with measured values in all the atmospheric windows covered by the NAST-I sensor. The
agreement obtained in the 800–980 cm−1 interval is generally better for the mixture of habits, but
solid columns produce smaller residuals in the 2000–2150 and 2400–2600 cm−1 spectral intervals.
Uncertainties related to the surface properties (i.e. skin temperature) are recognized to be the main
sources of error inthe infrared retrieval of cloud properties and affect thecomparison between forward
simulations and NAST-I data in all the infrared window bands not used for the inverse problem
Il monitoraggio dell’inquinamento acustico in ambito urbano a Potenza e proposta di modello di previsione del rumore
No full textL’inquinamento acustico da traffico veicolare in ambito urbano costituisce di certo una delle cause principali di riduzione della qualità della vita, per cui grande attenzione riveste oggi tale problematica nell'opinione pubblica. Lo studio in esame considera il monitoraggio dell’inquinamento acustico nel tessuto urbano della città di Potenza con riferimento a differenti tipologie stradali e in ore diverse della giornata al fine sia di verificare il tasso di inquinamento raggiunto rispetto ai limiti previsti dalle leggi vigenti, sia per confrontare i diversi modelli di previsione del rumore oggi disponibili in letteratura. Dalle considerazioni conseguenti all’implementazionee dei vari modelli vengono ricavate utili indicazioni per la messa a punto e conseguente proposta di un modello di previsione calibrato sulla città di Potenza, quale contributo del presente studio
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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