A 30-year (1964–1993) daily rainfall data base for the Spanish Mediterranean regions: first exploratory study

318

172

Precipitation trend analysis, on different spatial and temporal scales, has been of great concern during the past century because of the attention given to global climate change by the scientific community. According to some recent studies, the Italian territory has been suffering a precipitation decrease, especially in the last 50 years, and the southern areas seem to be more affected. The aim of the present study is to analyse rainfall time series over a wide time interval and a wide area, detecting potential trends and assessing their significance. For this purpose, 211 gauged stations, mainly located within the Campania region, southern Italy, have been analysed for the period 1918-1999. An accurate database has been set up through a data quality and time series homogeneity process. Statistical analysis of the database highlight that (1) the trend appears predominantly negative, both at the annual and seasonal scale, except for the summer period when it appears to be positive; (2) over the whole reference period, positive and negative trends are significant respectively for 9 and 27% of total stations and (3) over the last 30 years, a negative trend is instead significant for 97% of the total stations.

Section: Introductionmentioning

confidence: 53%

Trend analysis of annual and seasonal rainfall time series in the Mediterranean area

Longobardi

Villani

2010

318

172

“…Thus, along the Mediterranean coast, during 1964-1990, Romero et al (1998 found a global decrease in winter precipitation in 410 observatories, but González-Hidalgo et al (2006) reported a significant positive trend between 1951 and 2000 in the same area. A decrease in autumn precipitation was reported in the Gulf of Valencia (on the east coast) between 1961and 1990(González-Hidalgo et al, 2001 and an increase in summer precipitation (mainly inland) was observed during 1961-1990 by Mosmann et al (2004) using 333 observatories.…”

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%.

“…The Iberian Peninsula is an interesting area for such a study because the climate regime varies from temperate-maritime (in the northwest) to Mediterranean. In particular, the southeastern region of Spain has the lowest mean annual rainfall of any European region (Rodriguez-Puebla et al, 1998;Romero et al, 1998). The peninsula is affected by both Atlantic and Mediterranean influences (Rodó et al, 1997, Esteban-Parra et al, 1998Rodriquez-Puebla et al, 1998;Romero et al, 1998;Corte-Real et al, 1999;Serrano et al, 1999;Trigo and DaCamara, 2000), including the North Atlantic oscillation (NAO) (Hurrell, 1995;Rodó et al, 1997;Esteban-Parra et al, 1998;Marshall et al, 2001).…”

Section: Aims Of the Studymentioning

confidence: 99%

Links between circulation and changes in the characteristics of Iberian rainfall

Goodess

Jones

2002

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.