The climate observing system over
South America exhibits serious deficiencies in spatial resolution and
in data quality control. The FP6 CLARIS project aimed at building an
integrated high-quality daily meteorological station database and at
improving/automating quality control procedures. The CLARIS database
gathers stations from Argentina, Brazil, Uruguay and Chile, although
with a low spatial density, considering that most of these stations
were only provided by governmental institutions. However, in La Plata
Basin, many non-governmental institutions have their own networks and
can also provide good-quality data. Such data sources have been already
identified in CLIVAR/VAMOS/South American Low Level Jet Experiment
(SALLJEX) and could easily be integrated in an extended database, thus
creating a spatially dense daily observing station network. Such an
initiative is unique in La Plata Basin and will strengthen
collaborations with stakeholders who will provide the non-governmental
daily station data and are also interested by the CLARIS LPB results.
Such a high spatial density network will also improve daily gridded
products built with interpolation procedures developed in the EU FP6
project ENSEMBLES. Another deficiency of the
observing system in South America and more particularly in La Plata
Basin is the lack of long climate time series. Indeed, if one aims at
forecasting future climate variability and at quantifying its societal
impacts, it is crucial to evaluate both the natural and anthropogenic
climate signals. At short time horizons (2010-2040), the amplitude of
decadal-to-interdecadal variability may be as large as (or even larger
than) the amplitude of climate change signal. In order to quantify
these signals (one of the objectives of WP4), we need to describe
better the past variability at such time scales. Given that very few
long climate series are available in the region, proxy climate
reconstruction offers a complementary dataset allowing to have a better
description of past climate variability in La Plata Basin.
General objective
To improve the description of past climate
variability in LPB in order to provide an observational basis for
quantifying past climate variability (WP4 and WP6), evaluating climate
scenarios (WP4, WP5 and WP6) and providing high-quality data to WP7 for
impact model calibration (WP8 and WP9)
Specific objectives
• To build on
the FP6 CLARIS daily database to create a spatially highly-dense daily
database (precipitation, min/max temperature,
radiation, vapour pressure) and to develop and implement an automated
daily data homogeneization software for this large database. • To ensure the
sustainability of the CLARIS LPB initiatives through outreach and
collaboration with National Meteorological Services (NMSs) and
different local institutions. • To produce gridded products of daily observational data for climate model validation. • To describe
past decadal-to-interdecadal variability through proxy climate
reconstructions for the post-1850 period for climate model validation. • To summarise decadal-scale variability from instrumental and proxy climate reconstructions.
Task 3.1: Task 3.1 will be to
collect daily information originating from different institutions
(governmental and non-governmental) to improve the FP6 CLARIS
digitally-available records of daily weather data (maximum and minimum
temperature, precipitation, surface radiation and vapour pressure) over
La Plata Basin. Various series have been digitized during the
earlier CLARIS project. Here we will extend these to the present
through strengthened contacts with the National Meteorological Services
within the region.
Task 3.2: In the continuity
of the FP6 CLARIS project, where an automated software (in java) for
daily data consistency check has been implemented, task 3.2 will add
homogeneization procedures to the software. The final software
available to all the partners will allow consistency checks of the
CLARIS LPB daily climate data. This will additionally detect artificial
shifts in the time series, calculate any necessary homogenization
adjustments required for the time series, and provide 'infilled' time
series for impact models. (WP7, WP8, and WP9).
Task 3.3: In the FP6 project
ENSEMBLES, UEA has developed interpolation procedures to grid daily
precipitation totals and maximum and minimum temperatures, principally
for comparison with a range of Regional Climate Model (RCM) results.
For CLARIS LPB, we propose at UEA to undertake the same gridding
procedures and comparisons of the raw and gridded products. The density
of daily observations across LPB is markedly less than that available
for Europe, so the proposed resolution will be 0.5º by 0.5º
(latitude/longitude). Although gridding is undertaken at the daily
level, as in Europe the monthly totals/averages are conformed to agree
with earlier gridded UEA products, which use considerably more monthly
climatic data. The CLARIS LPB grids will additionally include radiation
and vapour pressure, as these variables will be required by many of the
impact sectors within WPs 8-9 to calculate potential
evapotranspiration. The daily gridded series will be used to validate
the RCM integrations undertaken over southern South America. Within the
timeframe of CLARIS LPB, it will not be possible to feed model
deficiencies back to the modelling centres, so instead, the differences
between the RCM integrations and the real-world gridded data (in terms
of means and variances) will be applied to future integrations of the
RCMs when these will be used for impact assessment.
Task 3.4: One goal of WP3 is
to extend the existing instrumental record backward in time by
developing proxy reconstructions for variables such as precipitation.
The latter will allow reconstruction of decadal timescale variability
of this parameter over longer timescales than the existing instrumental
data. In particular, we propose to reconstruct paleohydrological
variability through the study of lake records covering the last ~300
years in a region between 28° and 38°S. Thus, selected sites
will give us the opportunity to identify long-term hydrological
changes, affording the opportunity to gain insights into circulation
dynamics in South Eastern South America (SESA) during the last three
centuries. The chronology for the last centuries can be established
using radionucleides (226Ra and 210Pb) providing a decadal resolution
(Piovano et al., 2002).
Instrumental and historical records of Pampean lakes (from 28° to
38°S) show that long dry intervals characterized the first 75 years
of the 20th century, whereas positive hydrological balances have
occurred after the 1970s. Ongoing limnogeological research in central
Argentina has shown that the present wet phase has no precedent during
the past 300 years (Piovano et al., 2002, 2004 a, b, 2006). These
widely-known hydrological changes during the last quarter of the 20th
century have triggered increasing lake levels across the Pampas having
a major impact on human activities along the lake shorelines (e.g.,
Laguna Mar Chiquita, Melincué, Encadenadas from western Buenos
Aires province). Instrumental records of lake level change of Pampean
lakes during the 20th century are synchronous and in phase with
hydrological changes observed in La Plata basin (Piovano et al., 2002;
Sylvestre et al., 2007). Previous results further showed that the
reconstruction of past hydrological variability using well dated lake
sediments (limnogeology) enable us to reconstruct past hydrological
variabilities within a broad region of SESA.
The paleohydrological reconstructions will be coupled to a modelling
approach, including lake (i) -level, (ii)-salinity and (iii)-water
isotopic composition (δ18O and δD) simulation in response to
temperature and precipitation data (amount and isotopic composition).
The outcome of this approach will be used to test the impact of natural
climatic fluctuations and/or human activities, to assess the dominant
factors controlling these changes, and to quantitatively infer
hydro-climatic data from past reconstructions.
Task 3.5: A summary report on
the proxy and instrumental records in terms of decadal-to-interdecadal
variability. This report will also include other available data from
the area. This will assess how unusual the recent past, particularly
the period since the mid-1970s has been (all partners). The information
developed here will be used in particularly within WP4 and WP6