1,720,996 research outputs found
HOMOGENIZED SUNSHINE DURATION (1936-2013) AND GLOBAL RADIATION (1959-2013) INSTRUMENTAL TIME SERIES OVER ITALY: VARIABILITY AND TRENDS
Full text linkDaily sunshine duration (SD) and global radiation (Eg↓) series were recovered for the
whole Italian territory for the periods 1936-2013 and 1959-2013, respectively. To obtain
reliable series, useful to study the variability and trends, it has been necessary to solve
a number of problems concerning the quality of the data, their completeness and their
spatial distribution. Specifically, all the corresponding monthly records were subjected
to a detailed quality control and homogenization procedure in order to eliminate non climatic
signals and then the missing values were estimated. Moreover, all the series were
converted into seasonal and annual anomaly series and a 1◦x1◦ gridded version of the
dataset has been generated. Finally, two regional records (northern and southern Italy)
were obtained by averaging the corresponding grid-point series. Besides to all-sky records,
clear-sky anomaly records were also obtained selecting only the clear days in the original
series by comparison with corresponding total cloud cover (TCC) series.
The all-sky SD and Eg↓ anomaly regional records show a decreasing tendency (”Global
dimming”) between the 1950s and 1980s while in the subsequent period they show an increasing
tendency (”Brightening period”). The SD series, covering a longer period, show
also an increasing tendency between the mid-1930s and the mid-1950s (”Early brightening”).
The intensity and the length of the signals depend on the considered variable,
region and season. The comparison between SD records with corresponding TCC records
shows that the expected negative correlation between these variables is often not evident,
especially between the 1960s and 1980s. This suggests that during the dimming period
there is an important fraction of SD evolution that cannot be explained by TCC. It must
therefore depend on other factors, as for example, changes in aerosol optical thickness.
The clear-sky SD and Eg↓ series show longer and more significant trends than the all-sky
series for almost all the seasons. The most relevant changes are observed in winter and
autumn for both variables, highlighting the important role of clouds under all-sky conditions.
The resulting trends under clear-sky conditions are in agreement with changes in anthropogenic
aerosols suggesting that they have a relevant role on Eg↓ variability. Nevertheless,
an high correlation coefficient between Eg↓ series and the Sahel Precipitation index, especially
in the southern region, suggests also a significant contribution of natural aerosols.
This can justify the stronger dimming during spring, summer and autumn in the south
than in the north. Moreover, the fact that the intensity of the dimming/brightening trends change in all seasons removing the cloud contribution supports the hypothesis that clouds
contribute in a significant way to the Eg↓ variability under all-sky conditions.
The results highlight that the agreement between SD and Eg↓ decadal variability and
long-term trends, over the common period (1959-2013), depends on the considered region,
season and period. Specifically, Eg↓ clear-sky series show stronger tendencies than SD,
both during the dimming and brightening periods. In order to investigate whether the
differences in the clear-sky trends are due to a different sensitivity to atmospheric turbidity
changes, a model has been applied with the aim of estimating how large are SD and
Eg↓ relative variations when atmospheric turbidity (expressed by means of the Turbidity
Linke Factor - TL) changes. For low TL, Eg↓ is expected to be much more sensitive than
SD while for high TL, SD is expected to be slightly more sensitive than Eg↓. These results
give evidence that the use of SD as a proxy variable for clear-sky Eg↓ may be problematic,
especially if TL is low or if it shows significant changes in time. The comparison between
the modelled and the observed relative trends highlights a very good agreement with the
only exception of the dimming period in winter and autumn in northern region. These
disagreement could be both connected to instrumental problems or to the influence of
other meteorological variables.
Finally, a methodology to estimate Eg↓ normal values for any interval of a period in which
a SD anomaly series is available has been set up (it is very useful for example to evaluate
the ability of a RCM-GCM (Regional Climate Model - Global Climate Model) in capturing
the spatial distribution of Eg↓), and then, for each period during which the Eg↓ normal
values are available, to estimate the corresponding climatologies
Reconstructing sunshine duration and solar radiation long-term evolution for Italy: a challenge for quality control and homogenization procedures
No full textIn the last two decades, the scientific community has become aware of the fact that the real climate signal in original series of meteorological data is generally hidden behind non-climatic noise caused by a number of factors. Time series of meteorological data can therefore not be used for climate research without facing this issue. In this context, we have recently set up a database of Italian sunshine duration and solar radiation daily records and we have subjected them to a detailed quality check and homogenization procedure. Moreover, as the records are rather sparse and a significant fraction of them have wide gaps, we completed the data and set up a procedure in order to obtain at first a gridded version of the dataset and then average records that are representative of the entire Italian territory. The paper will highlight the main steps of the methodology that allowed us to get these average quality-checked and homogenized records and will discuss some open issues
A new database of cloudiness for Italy from instrumental time series since the late 19th century
No full textItaly has a very important role in the development of meteorological observations. Consequently, a heritage of data of enormous value has been accumulated in Italy over the last three centuries. However, only a small fraction of Italian data is available in computer readable form and the available records mainly concern temperature, precipitation and pressure. Within this context, we set up a project to recover as much as possible cloudiness Italian records. The goal is to consider total cloud cover (TCC), low and middle cloud cover, and cloud types. The data source we are using include the former national central office for meteorology (now CRA-CMA), the national air force meteorological and climatological service and some of the oldest Italian observatories as Milan, Rome, Turin
and Venice. The database contains sub-daily (from 3 to 8 observations per day for each station) information about TCC but also about the amount and the type of low, middle and high cloud in the sky. The oldest records start at about 1858 and about 30 records start in the 1880s. Currently quality check and test for temporal homogeneity is in progress. Then the monthly records will be completed by means of the neighboring records and averaged in order to get national and regional records for Italy and its main climatic areas. This new dataset will be presented and the results of the first analyses will be discussed. The study of cloudiness records for Italy is important also to better understand the behavior of sunshine duration, which shows a rather peculiar behaviour, especially in northern
Italy. In this area, in fact, we observe a statistically significant increasing tendency during the period 1936-2103, that most publications do not report, as a consequence of a strong increase starting from the 1980 and a less evident decrease in the previous period
Report on future evolution of sunshine duration and solar radiation over Sicily - Work package : WP6 – ENERGY – TASK 6.6 : past and future solar radiation estimation for Sicily
No full textThis report describes the activities performed by ISAC-CNR to produce Deliverable 6.13 of the
ECLISE Project - Future evolution of sunshine duration and solar radiation over Sicily. These activities
were performed within task 6.6 - Past and future solar radiation estimation for Sicily that also allowed
producing Deliverable 6.12 - Climatology of sunshine duration and solar radiation for Sicily. Both
deliverables were produced on the basis of SIAS (Servizio Informativo Agrometeorologico Siciliano,
one of the users of the ECLISE Project) needing. The deliverable mainly consists of maps reporting
monthly solar radiation climatologies for a number of time periods of 1961-2100 interval
Sicily monthly high resolution solar radiation climatologies and comparison with future projections
No full textWe developed a methodology to estimate solar radiation climatologies starting from a network of global radiation and/or sunshine duration records and a digital elevation model and applied it to a data set of 41 Sicilian global radiation records covering the 2002-2011.
All records were subjected to quality and homogeneity control. Moreover, the monthly record were subjected to a procedure aiming at estimate missing data.
The first step of the methodology consists in calculating global radiation monthly normals for all station sites or estimating them from sunshine duration normals, when global radiation data are not available.
The second step consists in estimating, the bias due to shading and adjusting the normal values in order to make them representative of un-shaded sites.
The third step consists in interpolating shading-bias-adjusted global radiation normals onto a 30 arc-resolution regular grid. This global radiation normals are then decomposed into the direct and diffuse components. Atmospheric turbidity is then evaluated over the same grid by means of the direct component obtained from shading-bias-adjusted global radiation.
The last steps consists in calculating direct, diffuse and reflected components of global radiation for any grid-cell, taking into account its slope and aspect and considering shading from the cell itself and from the neighboring cells. Knowing the direct, diffuse and reflected components, the global radiation can easily calculated by their sum.
This procedure will be presented and the resulting climatologies will be compared with those obtained from future projections (ENSEMBLES RCMs) with the objective to compare modelled and observed radiation climatologies
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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