In this study we have examined the spatial and temporal variability of the annual precipitation observations over the Iberian Peninsula (IP) for 47 years and 51 stations. Empirical orthogonal functions (EOFs) were obtained in order to characterise the variability. Four regional precipitation regimes have been identified and the corresponding principal components (PCs) were subjected to spectral analysis in order to obtain the structure of the temporal variations. The relationship between the precipitation and circulation patterns is also investigated. The four leading PCs of annual precipitation are associated with the following patterns: East Atlantic (EA); North Atlantic Oscillation (NAO); Southern Oscillation Index (SOI); Scandinavia (SCAND). The spectra of the precipitation PCs show statistically significant oscillations coherent with those found in the time series of the teleconnection indices. A reconstruction of the time series as a function of the PCs is provided in order to obtain a characterisation of precipitation climatology over the IP. © 1998 Royal Meteorological Society

Abstract. A growing interest in extreme precipitation has spread through the scientific community due to the effects of global climate change on the hydrological cycle, and their threat to natural systems' higher than average climatic values. Understanding the variability of precipitation indices and their association to atmospheric processes could help to project the frequency and severity of extremes. This paper evaluates the trend of three precipitation extremes: the number of consecutive dry/wet days (CDD/CWD) and the quotient of the precipitation in days where daily precipitation exceeds the 95th percentile of the reference period and the total amount of precipitation (or contribution of very wet days, R95pTOT). The aim of this study is twofold. First, extreme indicators are compared against accumulated precipitation (RR) over Europe in terms of trends using non-parametric approaches. Second, we analyse the geographically opposite trends found over different parts of Europe by considering their relationships with large-scale processes, using different teleconnection patterns. The study is accomplished for the four seasons using the gridded E-OBS data set developed within the EU ENSEMBLES project. Different patterns of variability were found for CWD and CDD in winter and summer, with north–south and east–west configurations, respectively. We consider physical factors in order to understand the extremes' variability by linking large-scale processes and precipitation extremes. Opposite associations with the North Atlantic Oscillation in winter and summer, and the relationships with the Scandinavian and East Atlantic patterns as well as El Niño/Southern Oscillation events in spring and autumn gave insight into the trend differences. Significant relationships were found between the Atlantic Multidecadal Oscillation and R95pTOT during the whole year. The largest extreme anomalies were analysed by composite maps using atmospheric variables and sea surface temperature. The association of extreme precipitation indices and large-scale variables found in this work could pave the way for new possibilities regarding the projection of extremes in downscaling techniques.

Winter precipitation variability over the Iberian peninsula was investigated by obtaining the spatial and temporal patterns. Empirical Orthogonal Functions were used to describe the variance distribution and to compress the precipitation data into a few modes. The corresponding spatial patterns divide the peninsula into climatic regions according to precipitation variations. The associated time series were related to large scale circulation indices and tropical sea surface temperature anomalies by using lag cross-correlation and cross-spectrum. The major findings are: the most influential indices for winter precipitation were the North Atlantic Oscillation and the East Atlantic/West Russian pattern; coherent oscillations were detected at about eight years between precipitation and the North Atlantic Oscillation and some dynamic consequences of the circulation on precipitation over the Iberian peninsula were examined during drought and wet spells. In the end statistical methods have been proposed to downscale seasonal precipitation prediction.

The aims of this study are to identify the trend of warm days and cold nights over the Iberian Peninsula and to connect the variations with large-scale variables. The reasons for performing this analysis are the effects that extremes events have on different ecosystems. Here, we present the results on spatial and temporal variability of warm days (TX90), or those exceeding the 90th percentile of maximum temperature, and cold nights (TN10), or those falling below the 10th percentile of minimum temperature. The extreme indices were derived from daily observations at stations and gridded data over land area for the period 1950 to 2006. Significant trends of more warm days and fewer cold nights were found. The trend to fewer cold nights is within the interval of global results given by the IPCC AR4 report; however, the trend to warm days is greater than the corresponding global trend. The influence of large-scale variables on these extreme indices was examined by means of the Empirical Orthogonal Function, correlation, composite maps and multiple regression analyses. Changes in TX90 are connected with the Scandinavian teleconnection index and a preferred mode of geopotential height at 500 hPa over the North Atlantic. Changes in TN10 are connected with the East Atlantic teleconnection index and the leading mode of Sea Surface Temperature (SST) variability over the North Atlantic area. Based on the links between the extreme indices and the large-scale variables we derived statistical models to describe the response of TX90 and TN10 to atmospheric circulation and SST variations. The 668 Climatic Change (2010) 100:667-684 models characterized the observed variations of TX90 and TN10 reasonably well. The results of this study encourage us to analyze, in further work, how temperature extremes might change over the Iberian Peninsula under warmer climate conditions.

[1] The consistency of two statistical downscaling methods and two different predictors to estimate past (last millennium) and future (21st century) precipitation in the Iberian and Scandinavian Peninsulas is assessed in the surrogate climate of a coupled climate model simulation. The methods are based on canonical correlation analysis and the search for analogs, with sea level pressure (SLP) and 500 mb geopotential height as predictors. The precipitation downscaled by the statistical methods within the simulated climate is compared with the direct model output. The estimation based on SLP alone agrees with the modeled precipitation on the Iberian Peninsula. However, the estimates for Scandinavia in the 21st century are drier than the target precipitation. Geopotential height as predictor performs worse than SLP in both regions yielding too dry future climate. Differences in both regions are analyzed in terms of relative humidity, which contributes to future precipitation changes of Scandinavian precipitation.

The trends of precipitation over the Iberian Peninsula (IP) and the North Atlantic Oscillation (NAO) index from December to March are compared using observations and model simulations from the Coupled Model Intercomparison Project phase 3 (CMIP3). The evaluation is performed in two multi-models as derived by averaging simulations corresponding to two experiments: one represents climate in the 20th century (20C3M) and the other the scenario with medium forcing IPCC SRES A1B in the 21st century. The NAO index shows a trend to more positive phases and precipitation tends to decrease in the case of observations, with greater significance in the NAO than in precipitation. The simulations in the 20th century underestimate the trend both in the NAO and in precipitation compared to observations. The multi-model in the 21st century indicates a change in the NAO regimes to being more positive; this leads to a reduction of precipitation over the IP. To explain the precipitation trend changes we consider the response of precipitation to the NAO, the regression between sea level pressure (SLP) over the Euro-Atlantic area onto precipitation averaged over the IP and the composite of precipitation for years with greater and lower NAO.

This study aims to provide new insight on the wheat yield historical response to cli-1 mate processes throughout Spain by using statistical methods. Our data includes observed wheat 2 yield, pseudo-observations E-OBS for the period 1979 to 2014, and outputs of general circula- 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64

Observational series of winter precipitation in the eastern part of the Cantabrian coast in the northern Iberian Peninsula are studied. This rather small area shows a clearly different interannual variability to the rest of the Peninsula. Series of winter precipitation for the whole area are defined using principal component (PC) analysis and they reflect the variability that can be attributed to changes in atmospheric circulation around the area. This variability is physically explained on the basis of the structure of baroclinic activity and vertically integrated moisture transports over the area derived from the NCEP/NCAR Reanalysis project. According to them, the leading PC of winter precipitation represents the overall precipitation over the area. Wet phases of this PC are associated to an increase of baroclinic activity leaving the eastern part of the Atlantic storm track and entering the Mediterranean basin. Conversely, dry phases show a strong reduction of baroclinic activity over the region. The second PC is linked to meridional water vapour transports over the area, which are affected by the topography of the region. Copyright