Javier Sigró - Academia.edu (original) (raw)

Papers by Javier Sigró

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Per bé que és en l'estudi de la temperatura on la comunitat científica internacional experta en l... more Per bé que és en l'estudi de la temperatura on la comunitat científica internacional experta en l'estudi observacional del clima dedica més esforços, la precipitació és igualment un element molt important del sistema climàtic. Bona part de les activitats desenvolupades per l'home i també els diferents ecosistemes naturals es veuen afectats pels canvis en el comportament de la precipitació. L'aigua és un recurs de primer ordre i tant la seva disponibilitat com també la seva qualitat són dues de les preocupacions de tota la societat. L'evident increment de la temperatura detectat a escala global (Jones i Moberg, 2003), està implicant una intensificació del cicle hidrològic i una més gran acumulació i circulació Resum La construcció de la sèrie regional de la precipitació del sector nord-oriental de la península Ibèrica durant el segle xx, a partir dels 121 observatoris que formen part de la base de dades ajustada de la precipitació mensual anomenada NESAP (Northeastern Spain Adjusted Precipitation), ha permès estimar les variacions i la tendència de la precipitació anual i estacional a la zona d'estudi. S'ha detectat un lleuger descens de la precipitació anual (-1,0%). S'han documentat valors positius tant a l'estiu com a la tardor i l'hivern (+7,4%, +6,2% i +1,8%, respectivament), mentre que la primavera ha experimentat una notable reducció (-21,8%). S'ha de destacar l'important descens ocorregut en aquesta mateixa estació durant el període 1971-2000 (-1,58% anual, que supera l'interval de confiança del 95%), i que coincideix amb el període de major increment tèrmic a la zona. Finalment, s'han definit un total de nou regions amb un comportament diferenciat de la precipitació.

Quaternary Science Reviews, 2021

We present the first reconstruction of past flood events variability in the Basque Country and We... more We present the first reconstruction of past flood events variability in the Basque Country and Western Ebro Basin (Northern Spain) integrating instrumental hydrological datasets (last 20 years), documentary archives (last 700 years) and Lake Arreo (655 m a.s.l.) sedimentary paleoflood record (last 1400 years). In this lake, allochthonous coarse and fine detrital layers (CDL and FDL respectively) intercalated within endogenic laminites were identified and interpreted as high-and moderate-energy flood events. The interplay between human activities and hydroclimate variability has controlled the deposition of these flood layers. Gauged data for the last 20 years suggest that floods are typically generated by heavy rainfall events on saturated soils after several days of continuous rainfall. These events occur mostly during the cold season (OcteMay). The reconstructed frequency of high-magnitude flood events from the lake record is coherent with the historical cold-season floods from Basque rivers. The lowest flood frequency took place during the 6e7 th and 10e15 th centuries, while higher flood frequency occurred during the 8 e9 th centuries and the last 500 years. Fluvial and lacustrine paleoflood records and documentary evidence show abrupt and large increases in extreme flood frequency during the termination of the Little Ice Age (1830e1870 CE) and mid to late 20 th century, both periods of Rapid Climate Change (RCC). The significant increase in flood frequency observed during RCC suggests that a similar pattern could be expected in the near future with the ongoing global warming.

Detecting and Modelling Regional Climate Change, 2001

The aim of this paper is to detect, estimate and characterise the existing variations and trends ... more The aim of this paper is to detect, estimate and characterise the existing variations and trends in surface air temperature in the Northeast of Spain, from the mid-nineteenth century onwards. To achieve this purpose, a new homogenised and gridded dataset of monthly mean maximum and minimum temperatures has been generated improving the spatial and temporal coverage of a previous study (Brunet, et al., 1999). The annual and seasonal averages of this data are analysed for the entire period (1869–1998) and partial time subsections in search of time variations and trends, by using usual statistical techniques (linear regression, filtering, change point detection, etc.).

Arreo Lake is a small (288 ha surface area) karstic lake 25 m deep located at the northwestern ed... more Arreo Lake is a small (288 ha surface area) karstic lake 25 m deep located at the northwestern edge of the Ebro Basin (NE Spain). The integration of sedimentary facies, element geochemistry, mineralogy, and biological proxies (pollen and diatoms), together with a robust chronological model provided by 15 AMS radiocarbon dating, 137Cs analyses, and varve counting, permitted a reconstruction of

The aim of this paper is to identify the existing relationship between summer maximum temperature... more The aim of this paper is to identify the existing relationship between summer maximum temperatures, regional atmospheric circulation patterns and sea surface temperatures. Spatial patterns identified at the Part I of this work have been employed and compared to those defined by the EMULATE project using the SANDRA method. and the SST from HadSST2 dataset. Our results indicate that sea surface temperature of the water masses surrounding the Iberian Peninsula exert the most important forcing over maximum summer temperatures. The Mediterranean coastal areas present higher correlations to SSTs (> 0.6) explaining 55% of summer June to August maximum temperatures. On the contrary, in the northern and central areas of the Iberian Peninsula is the end of the summer (August, September) when these marine variables explain a large portion of temperatures variance (62%)

Cuadernos de Investigación Geográfica, 2016

Long-term drought variability and trends were assessed in Barcelona at annual and seasonal scale ... more Long-term drought variability and trends were assessed in Barcelona at annual and seasonal scale for the period 1787-2014 and sub-periods 1851-2014, 1901-2014 and 1951-2014 to identify changes in drought patterns across time. High quality and adjusted monthly temperature and precipitation series were required for this purpose. The Standardized Precipitation Index (SPI), based on precipitation, and the Standardized Precipitation Evapotranspiration Index (SPEI), based on the difference between precipitation and reference evapotranspiration (ET0), were calculated to describe temporal drought fluctuations. Therefore, major droughts and wet events were identified and an accurate analysis of drought severity, magnitude and duration were also carried out.Both drought indices provided similar results related to drought variability and trends in Barcelona across time, although the SPEI showed larger drought severity than SPI especially during the second half of the 20th century. Trends analy...

The development of a daily historical European–North Atlantic mean sea level pressure dataset (EM... more The development of a daily historical European–North Atlantic mean sea level pressure dataset (EMSLP) for 1850–2003 on a 5° latitude by longitude grid is described. This product was produced using 86 continental and island stations distributed over the region 25°–70°N, 70°W–50°E blended with marine data from the International Comprehensive Ocean–Atmosphere Data Set (ICOADS). The EMSLP fields for 1850–80 are based purely on the land station data and ship observations. From 1881, the blended land and marine fields are combined with already available daily Northern Hemisphere fields. Complete coverage is obtained by employing reduced space optimal interpolation. Squared correlations (r 2) indicate that EMSLP generally captures 80%–90% of daily variability represented in an existing historical mean sea level pressure product and over 90% in modern 40-yr European Centre for Medium-Range Weather Forecasts Re-Analyses (ERA-40) over most of the region. A lack of sufficient observations over...

Science of The Total Environment

Journal of Climate

The aim of time series homogenization is to remove non-climatic effects, such as changes in stati... more The aim of time series homogenization is to remove non-climatic effects, such as changes in station location, instrumentation, observation practices, etc., from observed data. Statistical homogenization usually reduces the non-climatic effects, but does not remove them completely. In the Spanish MULTITEST project, the efficiencies of automatic homogenization methods were tested on large benchmark datasets of a wide range of statistical properties. In this study, test results for 9 versions, based on 5 homogenization methods (ACMANT, Climatol, MASH, PHA and RHtests) are presented and evaluated. The tests were executed with 12 synthetic/surrogate monthly temperature test datasets containing 100 to 500 networks with 5 to 40 time series in each. Residual centred root mean square errors and residual trend biases were calculated both for individual station series and for network mean series.The results show that a larger fraction of the non-climatic biases can be removed from station seri...

Earth System Science Data

Sub-daily meteorological observations are needed for input to and assessment of high-resolution r... more Sub-daily meteorological observations are needed for input to and assessment of high-resolution reanalysis products to improve understanding of weather and climate variability. While there are millions of such weather observations that have been collected by various organisations, many are yet to be transcribed into a useable format. Under the auspices of the Uncertainties in Ensembles of Regional ReAnalyses (UERRA) project, we describe the compilation and development of a digital dataset of 8.8 million meteorological observations of essential climate variables (ECVs) rescued across the European and southern Mediterranean region. By presenting the entire chain of data preparation, from the identification of regions lacking in digitised sub-daily data and the location of original sources, through the digitisation of the observations to the quality control procedures applied, we provide a rescued dataset that is as traceable as possible for use by the research community. Data from 127 stations and of 15 climate variables in the northern African and European sectors have been prepared for the period 1877 to 2012. Quality control of the data using a two-step semi-automatic statistical approach identified 3.5 % of observations that required correction or removal, on par with previous data rescue efforts. In addition to providing a new sub-daily meteorological dataset for the research community, our experience in the development of this sub-daily dataset gives us an opportunity to share some suggestions for future data rescue projects. All versions of the dataset, from the raw digitised data to data that have been quality controlled and converted to standard units, are available on PANGAEA:

In the Quaternary paleosciences, the rationale behind analogical inference presupposes that forme... more In the Quaternary paleosciences, the rationale behind analogical inference presupposes that former natural changes can be explained by causes operating now, although their intensity and rates can vary through time. In this paper we synthesise synthetize the results of different modern analog studies and discuss their value to obtain the best inferences from high resolution past records. This synthesis is based on the following: 1) The monthly monitoring of calcite precipitation reveals a strong connection with primary producers and between-years variability; this precipitation produces a seasonal signal with imprint on varve formation. 2) Clear pollen sedimentation peaks occur in spring/summer and fall/winter that coincide with temperature, precipitation, relative humidity and winds; this pattern converges with the two-layer coupled varves representing the same seasonality. 3) We assess the lake’s contemporary oxygenation dynamics over a three- year period; a combination of se...

The Science of the total environment, Jan 15, 2018

Recent expansion of anoxia has become a global issue and there is potential for worsening under g... more Recent expansion of anoxia has become a global issue and there is potential for worsening under global warming. At the same time, obtaining proper long-term instrumental oxygen records is difficult, thus reducing the possibility of recording long-term changes in oxygen shifts that can be related with climate or human influence. Varved lake sediments provide the better time frame to study this phenomenon at high resolution. We tracked the oxic/anoxic shifts of the varved Lake Montcortès since 1500CE, and tried to recognise anthropogenic and climatic influences combining biological and geochemical proxies. Four main scenarios emerged: 1) years with abrupt sediment inputs (A); 2) years with outstanding mixing and oxygenation of the water column (B); 3) years with strong stratification, anoxia, intense sulfur bacterial activity and increased biomass production (C); 4) years with stratification and anoxia, but relatively less biomass production (D). In line with current limnologic trends...

International Journal of Climatology, 2016