Regional climate change in Portugal: precipitation variability associated with large-scale atmospheric circulation

Corte‐Real, João; Qian, Budong; Hong, Xu

doi:10.1002/(sici)1097-0088(199805)18:6<619::aid-joc271>3.0.co;2-t

Cited by 163 publications

(138 citation statements)

References 19 publications

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“…Trigo and DaCamara (2000) showed a decrease in the frequency of cyclonic weather types in Portugal, and Piervitali et al (1997) and Brunetti et al (2000) did the same for Italy. Corte-Real et al (1998) indicated that the general decrease in precipitation identified in the Iberian Peninsula from 1960 to 1995 (Hisdal et al, 2001) coincides with the decrease in the frequency of weather types shown to generate precipitation (cyclonic, westerly and south-westerly) and also with an increase in anti-cyclonic weather types. Vicente-Serrano and López-Moreno (2006) found trends of types A and C opposite to the ones found herein, but for a grid centered over the Iberian Peninsula and for the 1952-1999 period, and a previous reclassification of type U days.…”

Section: Discussionmentioning

confidence: 92%

Determination of the Jenkinson and Collison’s weather types for the western Mediterranean basin over the 1948-2009 period. Temporal analysis

Grimalt¹,

Tomas²,

Alomar³

et al. 2013

Atmósfera

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Section: Discussionmentioning

confidence: 92%

Determination of the Jenkinson and Collison’s weather types for the western Mediterranean basin over the 1948-2009 period. Temporal analysis

Grimalt¹,

Tomas²,

Alomar³

et al. 2013

Atmósfera

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“…Automatic classifications are based on statistical techniques such as k-mean clustering (Matyasovszky et al, 1993), correlation (Yarnal, 1993), principal component analysis (PCA, Kutzbach, 1970;Deser and Blackmon, 1993;Wallace and Gutzler, 1981) or fuzzy rules (Pesti et al, 1996). Romero et al (1999) used a PCA in T-mode for weather-type classification in the Iberian Peninsula and, in the same region (Corte-Real et al (1998);Rasilla (2002) and Esteban et al (2005), used an algorithm that combines the k-mean clustering and the PCA for the same purpose.…”

Section: Analysis Of the Temporal Variability Of The Winter Atmosphermentioning

confidence: 99%

“…These authors obtained quantitative monthly series from the daily weather types by means of the sum of the number of weather types of each class during the month. Corte-Real et al (1998) used the same approach to summarise the monthly frequency of weather types in Portugal. In this paper, we followed this approach to create numerical monthly series of the frequency of each weather type.…”

Section: Analysis Of the Temporal Variability Of The Winter Atmosphermentioning

confidence: 99%

“…Other papers have analysed the influence of weather types on precipitation (Trigo and DaCamara, 2000;Goodess and Palutikof, 1998;Martín-Vide, 2002;Goodess and Jones, 2002;Corte-Real et al, 1998;Esteban et al, 2005). Nevertheless, at present there is no joint analysis of the relationship between the general atmospheric circulation modes in the North Atlantic region, the weathertype frequencies and the intensity and spatial differences of droughts, nor have detailed spatial scales been considered by means of a high density of weather stations, a method that would make it possible to accurately determine spatial and temporal patterns in a region of strong precipitation variability.…”

Section: Introductionmentioning

confidence: 99%

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The influence of atmospheric circulation at different spatial scales on winter drought variability through a semi‐arid climatic gradient in Northeast Spain

Vicente‐Serrano

López‐Moreno

2006

Intl Journal of Climatology

127

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This paper analyses the spatial and temporal variability of winter droughts in a semi-arid geographic gradient in Northeast Spain, from the Pyrenees in the north to the Mediterranean coastland in the south. Droughts that occurred between 1952 and 1999 were analysed by means of the Standardised Precipitation Index (SPI). The influence of the weather-type frequency and of the general North Atlantic atmospheric circulation patterns was analysed. The results indicate that winter droughts show an important spatial variability in the study area, differentiating three well-defined patterns. These correspond to the Pyrenees, the centre of the Ebro Valley, and the Mediterranean coastland. General negative trends in winter SPI have been found, which are indicative of the increase in winter drought conditions in the study area. Nevertheless, important spatial differences have also been recorded. Dominant north-south gradients in the influence of weather types are shown. Moreover, the negative trends in winter-SPI values agree with the negative trend in the frequency of the weather types prone to cause precipitation, such as the C, SW and W weather types and the increase in the frequency of A weather types. Nevertheless, in the Mediterranean coastland, the positive trend in SPI values agrees with the increase in the frequency of weather types of the east (E, SE), which are prone to cause precipitation in this area. Interannual variations in the frequency of the different weather types have been highly determined by different general atmospheric circulation patterns, mainly the North Atlantic Oscillation (NAO). Nevertheless, the correlation between the time series of weather-type frequency and the winter SPI is higher than that found between the SPI and the NAO. Thus, although the interannual NAO variability explains a high percentage of the interannual differences in the frequency of different weather types, it is not sufficient to explain the spatial and temporal variability of droughts, which respond better to atmospheric variability at more detailed (synoptic) spatial scales.

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“…Galambosi et al (1996), as did Bogardi et al (1993), selected the number of groups for the K-means method in a subjective way, denoting this as a typical subjective step in the automated classification procedure. In this way, and to analyse precipitation variability in Portugal in relation to large-scale circulation, Corte-Real et al (1998) applied an information measure based on the precipitation series for determining the optimal number of groups for K-means, eliminating subjectivity in this step of the classification. With T-mode and correlation matrix in PCA, and K-means CL previously oriented by Ward's hierarchical method, Romero et al (1999a) identified 19 atmospheric circulation patterns at two levels (925 and 500 hPa) related to significant rainfall days for Mediterranean Spain.…”

Section: Introductionmentioning

confidence: 99%

Daily atmospheric circulation catalogue for western Europe using multivariate techniques

Esteban

Martín‐Vide

Mases³

2006

Intl Journal of Climatology

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This study uses principal component analysis (PCA) and clustering (CL) techniques to characterize the daily surface synoptic circulation patterns over the region 30°N-60°N by 30°W-15°E, for the period 1960-2001 using the NCEP/NCAR Reanalysis Project data. The methodology used, previously proposed by Esteban et al. (2005) to identify heavy snowfall days over Andorra (Pyrenees), involves a pre-processing approach consisting of a spatial standardization of the data used for the rotated PCA on S-mode analysis and correlation matrix, and Varimax rotation of the retained components. For the clustering process, an alternative approximation based on the PCA results (positive and negative phases) to decide the centroids and the number of groups for the K-means clustering is shown, followed by the rejection of the iterations for this non-hierarchical algorithm. Twenty sea level pressure (SLP) circulation patterns were obtained, with all days classified. The composite maps for SLP and 500 hPa geopotential height (GPH), the monthly distribution, and the long-term variability for each of the circulation patterns is obtained. The results are consistent with the subjective knowledge of the daily atmospheric circulation over the area treated, and seem to be an easy and accessible way for the synoptic studies of short-lived (from weekly to daily) phenomena. In addition, this methodology appears to be applicable to all climatic areas of the world, as it characterizes well enough the complex circulation variability at mid-latitudes, including the surface low-pressure gradient patterns normally located over the Mediterranean in summer.

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Regional climate change in Portugal: precipitation variability associated with large-scale atmospheric circulation

Cited by 163 publications

References 19 publications

Determination of the Jenkinson and Collison’s weather types for the western Mediterranean basin over the 1948-2009 period. Temporal analysis

Determination of the Jenkinson and Collison’s weather types for the western Mediterranean basin over the 1948-2009 period. Temporal analysis

The influence of atmospheric circulation at different spatial scales on winter drought variability through a semi‐arid climatic gradient in Northeast Spain

Daily atmospheric circulation catalogue for western Europe using multivariate techniques

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