1,721,064 research outputs found
Remote sensing and electromagnetic modeling applied to weather and forward scatter radar
Full text linkThis dissertation deals with electromagnetic modelling and data analysis,
related to radar remote sensing and applied to forward scatter and meteorological
polarimetric systems. After an overview of radar fundamentals to
introduce the general terminology and concepts, results are presented at
the end of each chapter.
In this respect, a generalized electromagnetic model is first presented
in order to predict the response of forward scatter radars (FSRs) for airtarget
surveillance applications in both near-field and far-field regions.
The model is discussed for increasing levels of complexity: a simplified
near-field model, a near-field receiver model and a near-field receiver and
transmitter model. FSR results have been evaluated in terms of the effects
of different target electrical sizes and detection distances on the received
signal, as well as the impact of the trajectory of the moving objects and
compared with a customized implementation of a full-wave numerical
tool.
Secondly, a new data processing methodology, based on the statistical
analysis of ground-clutter echoes and aimed at investigating the monitoring
of the weather radar relative calibration, is presented. A preliminary
study for an improvement of the ground-clutter calibration technique is
formulated using as a permanent scatter analysis (PSA) and applied to
real radar scenarios. The weather radar relative calibration has been applied
to a dataset collected by a C-band weather radar in southern Italy
and an evaluation with statistical score indexes has drawn through the
comparison with a deterministic clutter map. The PSA technique has been
proposed using a big metallic roof with a periodic mesh grid structure and
having a hemispherical shape in the near-field of a polarimetric C-band
radar and evaluated also with an ad-hoc numerical implementation of a
full-wave solution.
Finally, a radar-based snowfall intensity retrieval is investigated at centimeter
and millimeter wavelengths (i.e., at X, Ka and W band) using a
high-quality database of collocated ground-based precipitation measurements
and radar multi-frequency observations. Coefficients for the multifrequency
radar snowfall intensity retrieval are empirically derived using
multivariate regression techniques and their interpretation is carried out
by particle scattering simulations with soft-ice spheroids.
For each topic, conclusions are proposed to highlight the goals of the
whole work and pave the way for future studies
Integrated Ground-Based Observing Systems: Applications for Climate, Meteorology, and Civil Protection
No full textThis volume presents a collection of selected articles based on presentations at the
seventh edition of the International Summer School on Atmospheric and Oceanic
Sciences (ISSAOS), annually organized by the University of L’Aquila, Italy. This
seventh edition, held during September 4–7, 2007 in the amazing venue of the
medieval Castle of the city of L’Aquila, focused on “Integrated Ground-Based
Observing System Applications for Climate, Meteorology, and Civil Protection.”
The goal of ISSAOS 2007 was to bring together experts and young researchers
in ground-based remote sensing to discuss the need for integrated systems and their
contribution to a variety of applications, including weather forecast, meteorology,
climatology, natural hazard monitoring, and transportation support.
Important questions related to weather, climate, etc., cannot be answered without
a broad view of the atmospheric processes and their mutual links. Ground-based
remote sensing provides useful tools to help understanding these processes by real
measurements with known error characteristics. The user needs for ground-based
remote sensing observations were reviewed at the first COST 720 workshop, incidentally
held in L’Aquila in 2002. Of course, all observing systems have strengths
and weakness, but none meet the breakthrough levels of user requirements for all
aspects. The solution to these requirements could be best met by a composite of
different observing systems.
The ISSAOS 2007-invited lecturers were Thomas Ackerman, Pier Paolo
Alberoni, Paolo Antonelli, Stefania Argentini, Laura Bianco, Stefano Decesari,
Piero Di Carlo, George L. Frederick, Frank S. Marzano, John Nash, Christian Pagé,
Vincenzo Rizi, Herman Russchenberg, David D. Turner, and James M. Wilczak.
A total of 70 people from 10 countries and 4 continents participated in ISSAOS
2007. The primary audience was constituted by graduate students in remote sensing
and atmospheric sciences, PhD students, and remote sensing researchers willing
to broaden their view concerning ground-based instrumentation, their synergy, and
applications. Following the tradition of ISSAOS, participants were asked to provide
an evaluation of the school at its conclusions. The results indicate that generally the
participants liked the school, including the quality of lecturers, the methodology,
and the venue. The overall organization and the social program were especially
appreciated by the vast majority.
v
vi Preface
The discussion during and following ISSAOS 2007 has been the starting point
for the preparation of the contributions in the present volume. The first part reports a
number of papers addressing the basic principles and the recent advances in groundbased
remote sensing of the atmosphere. The second part of the book reviews a list
of state-of-the-art applications of ground-based remote sensing integrated systems
to the study of climate, weather, and natural hazards. Even though this volume is
published after almost 3 years after the conclusion of ISSAOS 2007, it represents a
valuable sample of the state-of-the-art on ground-based remote sensing technology
and applications.
For the organization of ISSAOS 2007 we acknowledge the Center of Excellence
CETEMPS of the University of L’Aquila. We also acknowledge the financial
contribution from our sponsors (in alphabetic order): ELDES (http://www.eldes.
it/), HIMET (http://www.himet.it/), Kipp & Zonen (http://www.kippzonen.com/),
Leosphere (http://www.leosphere.com/), METEX (http://www.metek.de/), Radiometrics
(http://www.radiometrics.com/), Selex/Gematronik (http://www.gematroni
k.com/), and Vaisala (http://www.vaisala.com/). We greatly appreciated the sponsors’
delegates, the invited lecturers, and all the participants for enthusiastically
manifesting their interest in our idea. We are also grateful to Livio Bernardini,
Klaide De Sanctis, Sabrina Gentile, Emanuela Pichelli, Daniela Ronconi, Enrico
Stagnini, and Paolo Stocchi for helping with the organization and the logistic.
Federica Casilli and Luigi Margherita deserve particular gratitude for their kind
help throughout the project.
Finally, this book inevitably carries signs of the tragic earthquake event in
L’Aquila on April 6, 2009. Our most sincere thoughts go the many that have lost
lives and beloved ones during that tragic event
Flower elliptical-orbit constellation exploiting millimetre-wave radiometry and radio occultation for meteo-climatological applications
Full text linkThis paper reports on the potential of combining
elliptical-orbit Flower constellations with millimeter-wave radiometry and
radio-occultation, a mission concept briefly named FloRad2. The advantages
of flower constellation with respect to conventional orbits are discussed,
including the flexibility ensuring increasing coverage with separate
launches. Millimeter-wave radiometry and radio-occultation receivers provide
the advantage to design fairly compact payloads that comply well with
current technology of mini-satellites. Millimeter-wave radiometry and
radio-occultation techniques are somewhat complementary and an optimal
combination of these observations results in atmospheric products with
enhanced vertical and horizontal resolutions. Thus, the combination of
small, light payloads employing millimeter-wave radiometry and
radio-occultation with Flower elliptical-orbit constellations may result in
an optimal compromise between retrieval performances and system complexity
that is ideal for continued long-term missions with meteorological and
climatological applications
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
Modeling and measurements of rainfall by ground-based multispectral microwave radiometry
No full textThe potential of ground-based multispectral microwave
radiometers in retrieving rainfall parameters is investigated
by coupling physically oriented models and retrieval methods
with a large set of experimental data. Measured data come from
rain events that occurred in the USA at Boulder, Colorado, and
at the Atmospheric Radiation Measurement (ARM) Program’s
Southern Great Plains (SGP) site in Lamont, OK. Rain cloud
models are specified to characterize both nonraining clouds,
stratiform and convective rainfall. Brightness temperature numerical
simulations are performed for a set of frequencies from
20 to 60 GHz at zenith angle, representing the channels currently
deployed on a commercially available ground-based radiometric
system. Results are illustrated in terms of comparisons between
measurements and model data in order to show that the observed
radiometric signatures can be attributed to rainfall scattering
and absorption. A new statistical inversion algorithm, trained by
synthetic data and based on principal component analysis is also
developed to classify the meteorological background, to identify the
rain regime, and to retrieve rain rate from passive radiometric observations.
Rain rate estimate comparisons with simultaneous rain
gauge data and rain effect mitigation methods are also discussed
Combining microwave radiometer and wind profiler radar measurements for high-resolution atmospheric humidty profiling
No full textA self-consistent remote sensing physical method to retrieve atmospheric humidity high-resolution profiles
by synergetic use of a microwave radiometer profiler (MWRP) and wind profiler radar (WPR) is
illustrated. The proposed technique is based on the processing of WPR data for estimating the potential
refractivity gradient profiles and their optimal combination with MWRP estimates of potential temperature
profiles in order to fully retrieve humidity gradient profiles. The combined algorithm makes use of recent
developments in WPR signal processing, computing the zeroth-, first-, and second-order moments of WPR
Doppler spectra via a fuzzy logic method, which provides quality control of radar data in the spectral
domain. On the other hand, the application of neural network to brightness temperatures, measured by a
multichannel MWRP, can provide continuous estimates of tropospheric temperature and humidity profiles.
Performance of the combined algorithm in retrieving humidity profiles is compared with simultaneous in
situ radiosonde observations (raob’s). The empirical sets of WPR and MWRP data were collected at the
Atmospheric Radiation Measurement (ARM) Program’s Southern Great Plains (SGP) site. Combined
microwave radiometer and wind profiler measurements show encouraging results and significantly improve
the spatial vertical resolution of atmospheric humidity profiles. Finally, some of the limitations found in the
use of this technique and possible future improvements are also discussed
Multivariate probability matching of Satellite Infrared and Microwave Radiometric Measurements for Rainfall Retrieval at the Geostationary Scale
No full textVariations 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
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