DATA AND METADATA FOR THE CENTRAL PART OF THE MEDITERRANEAN BASIN: LESSONS FROM THE CLIMAGRI PROJECT

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DATA AND METADATA FOR THE CENTRAL PART OF THE
MEDITERRANEAN BASIN LESSONS FROM THE CLIMAGRI
PROJECT

• Maurizio Maugeri
• Istituto di Fisica Generale Applicata via
  Celoria 16 Milano
• Istituto di Scienze dell'Atmosfera e del Clima
  via Gobetti 101 - Bologna
• maurizio.maugeri_at_unimi.it

Tarragona November 28th, 2007
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Italy has a very important role in the
development of meteorological observations

• Invention of some of the most important
  meteorological instruments (thermometer,
  barometer).
• Establishment of the first network of
  observations (rete del Cimento, set up by
  Galileos scholars).

The strong Italian presence in the development of
meteorological observations is also testified by
six stations that have been in operation since
the eighteenth century (Bologna, Milan, Rome,
Padua, Palermo and Turin) and other 15 stations
where observations started in the first half of
the nineteenth century (Aosta, Florence, Genoa,
Ivrea, Locorotondo, Mantua, Naples, Parma, Pavia,
Perugia, Trento, Trieste, Udine, Urbino and
Venice).
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As a consequence, a heritage of data of enormous
value has been accumulated in Italy over the last
three centuries
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This heritage has been known for a long time and
many attempts have been made to collect data into
a meteorological archive..

• Cantù V. and Narducci P. (1967) Lunghe serie di
  osservazioni meteorologiche. Rivista di
  Meteorologia Aeronautica, Anno XXVII, n. 2,
  71-79.
• Eredia F. (1908) Le precipitazioni atmosferiche
  in Italia dal 1880 al 1905. In Annali
  dell'Ufficio Centrale di Meteorologia. Serie II,
  Vol. XXVII, anno 1905, Rome.
• Eredia F. (1919) Osservazioni pluviometriche
  raccolate a tutto l'anno 1915 dal R. Ufficio
  Centrale di Meteorologia e Geodinamica. Ministero
  dei Lavori Pubblici, Rome.
• Eredia F. (1925) Osservazioni pluviometriche
  raccolate nel quinquennio 1916-1920 dal R.
  Ufficio Centrale di Meteorologia e Geodinamica.
  Ministero dei Lavori Pubblici, Rome.
• Mennella C. 1967. Il Clima d'Italia. Napoli
  Fratelli Conti Editori, 724 pp.
• Millosevich (1882) Sulla distribuzione della
  pioggia in Italia. In Annali dell'Ufficio
  Centrale di Meteorologia. Serie II, Vol. III,
  anno 1881, Rome.
• Millosevich (1885) Appendice alla memoria sulla
  pioggia in Italia. In Annali dell'Ufficio
  Centrale di Meteorologia. Serie II, Vol. V, anno
  1883, Rome.
• Narducci, P., 1991 Bibliografia Climatologica
  Italiana, Consiglio Nazionale dei Geometri, Roma.

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however, in spite of the huge heritage of data
and even if most records were subjected to some
sort of analysis, until a few years ago only a
small fraction of Italian data was available in
computer readable form
Archivio delle serie secolari UCEA - Anzaldi C.,
Mirri L. and Trevisan V., 1980 Archivio Storico
delle osservazioni meteorologiche, Pubblicazione
CNR AQ/5/27, Roma.
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Within this context, a number of projects where
set up in Italy in the last 5 to 10 years to
recovery as much as possible secular
meteorological records
The activities can be clustered in two general
classes
Projects concerning single stations High temporal
resolution, complete metadata documentation, etc
Projects concerning national/regional
networks Lower temporal resolution, less
metadata, etc
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Projects concerning single stations are
particularly important for the records beginnig
in the 18th century
Milan a 10-year project developed by
Osservatorio Astronomico di Milano-Brera and
Milan University allowed to recovery metadata
and daily T, P, R records
Padova as for Milan but activities performed by
Istituto di Scienze dell'Atmosfera e del Clima
section of Padova
Torino as for Milan and Padova but activities
performed by Società Meteorologica Italiana
Palermo recovery started later on The
activities are performed by Os. Astronomico.
Available metadata and daily R and T records.
Bologna as for Milan, Padova and Torino for the
data after 1813. Still in progress for the 18th
century data
Roma as for Milan, Padova and Torino for the
data after 1862. Only monthly data for the 18th
century
there is a lot of still unexploited
information Cloudiness, sunshine, vapour
pressure, wind, etc
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Projects concerning national/regional networks
Second part of the 1990s the CNR project
Reconstruction of the past climate in the
Mediterranean area allowed the UCEA secular
series data set to be updated, completed, and
revised. In spite of significant improvements,
the new data set had the fundamental limitation
of very poor metadata availability. Moreover, the
number of stations was still too low. So
homogenisation could not be performed. Around
2000 a new research programme was established. It
was initially developed within a national project
(CLIMAGRI), then an extension of the activities
was performed within some other projects. Thanks
to the availability of resources from more
projects and to additional results from other
projects, the initial goal of homogenising the
existing records was extended and the
construction of a completely new and larger set
of data and metadata was also planned.
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• The new dataset of Italian secular records

• Meteorological variables
• Air Temperature (minimum, mean, maximum)
• Precipitation
• Air Pressure
• Cloud Cover
• Other data

Temporal resolution Daily/Monthly
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The new Italian dataset air temperature
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The new Italian dataset air temperature
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The new Italian dataset precipitation
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The new Italian dataset precipitation
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The new Italian dataset other variables
the activities are still in progress (e.g. EU
project ALP-IMP). They concern air pressure,
cloud cover, humidity and snow
AIR PRESSURE (secular records)
CLOUD COVER (secular records)
SNOW (HS snow at ground HN fresh snow) daily
/ monthly data About 15 records of northern Italy
HUMIDITY (i.e. dry / wet temperatures) daily
data 2 records
1951-2004 PERIOD All variables available in
digital format Italian Air Force data-set.
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The new Italian dataset metadata

• Metadata collection was performed with two main
  objectives
• to understand the evolution of the Italian
  meteorological network
• to reconstruct the history of all the stations
  of the data-set.

The research on the history of the single
stations was performed both by analysing a large
amount of grey literature and by means of the
UCEA archive. All information was summarized in
a card for each data series. Each card is
divided into three parts. In the first part all
the information obtained from the literature is
reported. In the second part there are abstracts
from the epistolary correspondence between the
stations and the Central Office. In the third
part the sources of the data used to construct
the record are summarized.
For full details see CLIMAGRI project WEB site
(www.climagri.it)
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The new Italian dataset quality and homogeneity
issues

• The problem the real climate signal, that we try
  to reconstruct studying long (secular) records of
  meteorological data, is generally hidden behind
  non-climatic noise caused by station relocation,
  changes in instruments, changes in observing
  times, observers, and observing regulations,
  algorithms for the calculation of means and so
  on.
• ? climatic time series should not be used for
  climate research without a clear knowledge about
  the state of the data in terms of quality and
  homogeneity.

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Classification of the institutions (Observatory,
high school, etc)? Data sources (hand-written
original observations year books pre existing
data sets, etc) ? Time resolution (yearly,
monthly, daily, etc)? Comparison with other
records
Quality
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Homogeneity
Climate variations
Measuring problems
Signals in the records of meteorological data
Measuring problems Relocations Instrumental
errors (changes of the instruments
and/or recalibrations) Observation
methods Screenings Changes in the environment
around the station
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The problem is not easy to manage
Meteorological series can be tested for
homogeneity and homogenised both by direct and
indirect methodologies. The first approach is
based on objective information that can be
extracted from the station history or from some
other sources, the latter uses statistical
methods, generally based on comparison with
other series. Both direct and indirect
methodologies have severe limits
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Direct methodologies are not easy to use as 1)
it is generally very difficult to recover
complete information on the history of the
observations (metadata)2) even if available,
metadata hardly give quantitative estimates of
the inhomogeneities in the measures. Also
indirect methodologies have important
deficits1) they require some hypothesis about
the data (e.g. homogeneous signals over the same
region)2) inhomogeneities and errors are
present in all meteorological series, and so it
is often difficult to decide where to apply
corrections and, when the results are not clear
there is a high risk of applying subjective
corrections.
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• How to overcome the intrinsic limit of indirect
  homogenisation methods is, at present, still an
  open question.
• The possibilities range from homogenising all
  suspect periods, to correcting the series only if
  the results of the statistical methods are very
  clear and also supported by metadata.

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• So, at present, an universal approach to manage
  the problem is lacking.
• Our approach

• Collecting as much metadata as possible
• Performing a first homogenisation by means of
  direct methologies
• 3) Performing final homogenisation by means of
• indirect methologies

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• Basic problem what is to correct?
• a) All the periods given by statistical methods
• b) Only the periods for which there is evidence
  in metadata

The problem is open
Our methodology Wide use of statistical
methods Critical analysis on the light of metadata
The CLIMAGRI project
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Important open question trends critically depend
on the methods used to homogenise the data
North Italy long-term temperature evolution
(filtered curves) in the 1876-1996 period
according to Brunetti et al. (2000) and Boehm et
al. (2001).
Adapted from Brunetti, M., Buffoni, L., Maugeri,
M., Nanni, T., 2000 Trends of minimum and
maximum daily temperatures in Italy from 1865 to
1996. Theor. Appl. Climatol., 66, 49-60 and Böhm,
R., Auer, I., Brunetti, M., Maugeri, M., Nanni,
T., Schöner W., 2001 Regional Temperature
Variability in the European Alps 1760-1998 from
homogenised instrumental time series. Int. J.
Climatol., 21, 1779-1801.
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Important open question trends critically depend
on the methods used to homogenise the data
Long-term evolution of summer temperatures in the
1775-2003 period according to Auer et al. (2007)
and Brunetti et al. (2006).