Torrential rainfall in northeast of the Iberian Peninsula: synoptic patterns and WeMO influence

International audienceThis study presents a catalogue of synoptic patterns of torrential rainfall in northeast of the Iberian Peninsula (IP). These circulation patterns were obtained by applying a T-mode Principal Component Analysis (PCA) to a daily data grid (NCEP/NCAR reanalysis) at sea level pressure (SLP). The analysis made use of 304 days which recorded >100 mm in one or more stations in provinces of Barcelona, Girona and Tarragona (coastland area of Catalonia) throughout the 1950?2005 period. The catalogue comprises 7 circulation patterns showing a great variety of atmospheric conditions and seasonal or monthly distribution. Likewise, we computed the mean index value of the Western Mediterranean Oscillation index (WeMOi) for the synoptic patterns obtained by averaging all days grouped in each pattern. The results showed a clear association between the negative values of this teleconnection index and torrential rainfall in northeast of the IP. We therefore put forward the WeMO as an essential tool for forecasting heavy rainfall in northeast of Spain

The consecutive disparity of precipitation in conterminous Spain

Precipitation irregularity constitutes a constraint for natural systems and socio-economic activities, particularly in water-scarce environments. Standard variability statistics such as the standard deviation, variance, and coefficient of variation do not consider the chronological order of these values. In Climatology, however, the temporal order of meteorological events is a relevant factor that can affect natural and socio-economic systems. In order to evaluate the disparity between consecutive values in precipitation series, we applied the Consecutive Disparity Index (D) to the monthly grid with the highest spatial resolution (10×10 km) existing in Peninsular Spain for the period December 1915–November 2015. Monthly, seasonal, and annual D values show an increase from north to southwest, especially in July and August. The D values for the month-to-month correlative series and for monthly mean precipitation reveal a relatively similar pattern. In the latter case, however, the low values are recorded towards southern Spain, following some mountain ranges in the Centre-East of the territory. Monthly, seasonal, and annual precipitation values are also negatively correlated with the corresponding D values. © 2021, The Author(s)

Overview of the IBER-STILLING project: Assessment and attribution of wind speed and wind gust variability

Trabajo presentado en EGU General Assembly, celebrada en modalidad virtual del 4 al 8 de mayo de 2020.In a context of global climate change, the scientific community has evidenced a significant decrease in wind speed, a phenomenon known as «stilling». This climate trend has mainly been observed over mid-latitude continental surfaces since the 1980s. On the contrary, other studies have detected an increase in wind speed over ocean surfaces; and there is little conclusive scientific evidence on trends in wind speed across the troposphere. Furthermore, a reversal in global terrestrial stilling has recently been documented in few regional and global studies since the 2010s. The causes associated with the climate variability of wind speed have not yet been resolved and there are many uncertainties behind the «stilling» and «recovery» phenomenon because neither the quantity nor the quality of wind speed observations is adequate. This contribution shows an overview of the IBER-STILLING project (RTI2018-095749-A-I00) funded by the Spanish Ministry of Science, Innovation and Universities. This project aims to move forward on the assessment of wind speed and wind gusts variability and underlying causes globally, with emphasis on the Spanish territory and surrounding ocean (Atlantic) and sea (Mediterranean) surfaces. The IBER-STILLING project will collect and generate climate information of wind speed from different data sources; climate data will be subject to a comprehensive protocol for quality control and homogenization. The statistical analysis of these climate databases will allow characterizing trends and climatic cycles of wind speed, allowing a pioneering global analysis of wind speed over continental and ocean surfaces, and across the boundary layer and the entire troposphere. The project will also conduct wind-tunnel experiments to quantify biases introduced by anemometers devices

Climate controls on rainfall isotopes and their effects on cave drip water and speleothem growth: the case of Molinos cave (Teruel, NE Spain)

The interpretation of stable isotopes in speleothems in terms of past temperature variability or precipitation rates requires a comprehensive understanding of the climatic factors and processes that influence the δ18O signal in the way through the atmosphere to the cave, where carbonate precipitates acquiring its final isotopic composition. This study presents for the first time in the Iberia Peninsula an integrated analysis of the isotopic composition of rainfall (δ18Op) during 2010–2012 years and, through a detailed monitoring survey, the transference of the primary isotopic signal throughout the soil and epikarst into the Molinos cave (Teruel, NE Spain). Both air temperature and amount of precipitation have an important effect on δ18Op values, clearly imprinting a seasonal variability modulated by an amount effect when rainfall events are more frequent or intense. Air mass history and atmospheric circulation influences are considered through the study of weather types, synoptic-scale climate patterns and large-scale atmospheric circulation indexes (North Atlantic Oscillation and Western Mediterranean Oscillation) revealing a dominant source effect on δ18Op values in this region where tropical North Atlantic and Western Mediterranean are the two moisture source regions. A delay of 2–3 months occurs between the dripwater oxygen isotopic composition (δ18Od) respect to δ18Op values as a consequence of large residence time in the epikarst. Limited calcite precipitates are found from winter to spring when δ18Od values are less negative and dripwater rates are constant. This study suggests that NE Iberian δ18Ocalcite proxy records are best interpreted as reflecting a combination of parameters, not just paleotemperature or paleorainfall and, if extending present-day situation towards the recent past, a biased signal towards winter values should be expected in Molinos speleothem records

Trends in frequency indices of daily precipitation over the Iberian Peninsula during the last century

This study provides the first long-term assessment of changes in precipitation associated with different rainfall categories over the Iberian Peninsula (IP). Using recently digitized data from 27 stations in Portugal and Spain, we have examined trends of precipitation indices for the complete period 1903–2003 and the two subperiods 1903–1953 and 1954–2003. These indices were evaluated seasonally according to five rainfall categories: total rainfall (=0.2 mm), light rainfall (=0.2 an