Precipitation seasonality in eastern and southern coastal Spain

293

239

Investigation of the links between atmospheric circulation patterns and rainfall is important for the understanding of climatic variability and for the development of empirical circulation-based downscaling methods. Here, spatial and temporal variations in circulation-rainfall relationships over the Iberian Peninsula during the period 1958-97 are explored using an automated circulation classification scheme and daily rainfall totals for 18 stations. Links between the circulation classification scheme and the North Atlantic oscillation (NAO) are also considered, as are the direct links between rainfall and the NAO. Trends in rainfall and circulation-type frequency are explored. A general tendency towards decreasing mean seasonal rainfall over the peninsula, with the exception of the southeastern Mediterranean coast, hides larger changes in wet day amount and rainfall probability. There is a tendency towards more, less-intensive rain days across much of Iberia, with a tendency towards more, more-intensive rain days along the southeastern Mediterranean coast, both of which are reflected in changes in rainfall amount quantiles. A preliminary analysis indicates that these changes may have occurred systematically across all circulation types. Comparison of the trends in rainfall and in circulationtype frequency suggests possible links. These links are supported by linear regression analyses using circulation-type frequencies as predictor variables and rainfall totals for winter months as the predictands. The selected predictor variables reflect the main circulation features influencing winter rainfall across the peninsula, i.e. the strong influence of Atlantic westerly and southwesterly airmasses over much of the peninsula, of northerly and northwesterly surface flow over northern/northwestern Spain and northern Portugal and the stronger effect of Mediterranean rather than Atlantic influences in southeastern Spain. The observed rainfall changes cannot, however, be explained by changes in circulation alone.

Section: Circulation Typesmentioning

confidence: 73%

Section: Aims Of the Studymentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

Links between circulation and changes in the characteristics of Iberian rainfall

Goodess

Jones

2002

293

239

“…As a consequence of this heterogeneity, annual trends are characterized globally by a general decrease in precipitation (−12%), with increased variability to the south of the Gulf of Valencia, but a decrease in the north in the period 1951-2000. Sumner et al (2001) suggested that socioeconomic problems require a detailed analysis of precipitation in these areas of Spain, which is true, as since 1950, the population has grown by 86.2% over the study area as a whole, with growth in the coastal provinces rising to 107.3%, but only to 27.6% inland. Furthermore, the inland population is mainly concentrated in a small number of towns and the rural exodus continued up to the early 1980s, particularly in mountain areas.…”

Section: Discussionmentioning

confidence: 99%

Seasonal precipitation trends in the Mediterranean Iberian Peninsula in second half of 20th century

Luis¹,

Gonzalez‐Hidalgo²,

Longares³

et al. 2008

121

This is a study of the changes in annual and seasonal precipitation amounts and variability, during the period 1951-2000, using MOPREDA MES . This dataset includes 1113 complete and homogeneous monthly precipitation time series from the Mediterranean Iberian Peninsula (IP), and corresponds to the five official Spanish hydrological divisions which drain into the Mediterranean Sea. The time series of annual and seasonal precipitation were used to test for trends. The absolute value of the anomaly time series was also tested for trends to identify changes in interannual variability of precipitation. The significance of these changes was assessed using the non-parametric Spearman rank test. The intensities of observed changes, both on mean values and variability, were estimated by using linear regression techniques. Finally, we analysed the area affected by different trends by using raster maps and spatial statistics, in addition to calculating the global balances for the five hydrological divisions. We detected high variability in precipitation regimes and conditions in the study area; nevertheless, a decrease in seasonal and annual precipitation has predominated in the east of the IP during the second half of the 20th century. On an annual scale, precipitation has diminished over 90.1% of the study area. Additionally, a high percentage of the territory was affected by diminishing precipitation at a seasonal level: 85% (of territory) in summer, 82% in spring, 64% during winter and 61% in autumn. Taking the study area as a whole, seasonal precipitation decreases are ranked as follows: summer (−22.5%), spring (−19.3%), winter (−7.3%), and autumn (−5.2%), with a decrease in the value of the global mean annual precipitation −12.4%. We also detected an increase of precipitation variability in winter (+23.5%) and summer (+11.4%), and a decrease in autumn and spring (−14.9 and −16.8%, respectively) with a global mean value of +7.8%.

“…A wider geographical scale that includes the Catalan territory has been adopted by different workers in their research on the annual, seasonal and monthly rainfall regime of the Iberian Peninsula, by means of principal component (PC) techniques (Fernández-Mills, 1995;Esteban-Parra et al, 1998;Rodríguez-Puebla et al, 1998;Serrano et al, 1999;García et al, 2002) and of the Spanish Mediterranean area (Romero et al, 1998(Romero et al, , 1999aSumner et al, 2001). In all the aforementioned cases, daily data were used to obtain monthly, seasonal and annual amounts, which constituted the database for these studies.…”

Section: E D I T E R R a N E A N S Ementioning

confidence: 99%

Spatial and temporal variability of the daily rainfall regime in Catalonia (northeastern Spain), 1950–2000

Lana

Martínez

Serra

et al. 2004

Spatial and temporal patterns in the daily rainfall regime of Catalonia (northeastern Spain) recorded for the 1950-2000 period are analysed from several points of view, including the irregularity of the time series in terms of entropy, the Mann-Kendall test for time trends, a principal component analysis (PCA), an average linkage (AL) clustering algorithm and, finally, a power spectrum analysis, which includes a comparison of white-noise and Markovian red-noise hypotheses. The analyses are based on three monthly variables derived from the amounts recorded on a daily basis: the average daily rainfall and the standard deviation of the daily rainfall for each month, together with the corresponding coefficient of variation. The joint spatial-temporal variability is manifested by the irregularity index, which is characterized by relevant values in all cases and gradients from the north (Pyrenees and Pre-Pyrenees mountain ranges) to the south (Ebro Valley) and to the Mediterranean coast. The interpretation of the factor scores derived from the PCA and of the clusters obtained from the AL algorithm also describes the complex spatial distribution of the daily rainfall regime, given that the effects of atmospheric circulation patterns on rainfall regimes are conditioned by the complex orography of Catalonia and its proximity to the Mediterranean Sea. The factor loadings associated with the PCA also suggest a distinction between hot, cold and mild seasons. Finally, it is worth noting that monthly series are usually accompanied by white background noise and, in a few cases, signs of Markovian behaviour and some significant periodicities, which are generally of less than 10 months and which change from one cluster to another.