Trends affecting pluviometric indices at the Fabra Observatory (Barcelona, NE Spain) from 1917 to 1999

• Published in: International Journal of Climatology
• Main Authors: Lana, X., Serra, C., Burgueño, A.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2003
• Subjects: North Atlantic; North Atlantic oscillation
• Online Access: http://dx.doi.org/10.1002/joc.882; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fjoc.882; https://rmets.onlinelibrary.wiley.com/doi/pdf/10.1002/joc.882

Abstract A set of daily rainfall amounts collected at the Fabra Observatory (Barcelona, NE Spain) from 1917 to 1999 has made it possible to compute several pluviometric indices at seasonal and annual scales for every year, after applying a low‐pass filter. The first index is obtained by considering the time series of seasonal and annual rainfall amounts. The next two indices evaluate the number of days equalling or exceeding a threshold rainfall level and the average intensity for these days. These procedures are applied to different threshold rainfall levels accounting for all rainy days and the sets of days reaching the 25, 50 and 75% percentile of daily rainfall amounts. The fourth index is defined as the quotient between cumulative rainfall for some class intervals and the total rainfall. Daily amounts falling within the <25, 25–50, 50–75, 75–90 and ≥90% percentile rainfall amounts define the class intervals. Additionally, the same indices are also calculated for the 95% percentile of rainy days, which correspond to outstanding daily amounts. A detailed analysis of the trends affecting all these indices and their statistical significance suggests the effects of a possible climatic change on the pluviometric regime of the Fabra Observatory over the course of the 20th century. Moreover, the resulting trends are compared with those inferred from data from around the planet during the 20th century and with other Mediterranean rain gauges. By comparing this with regional rain data series, the possibility of the heat island effect of the city of Barcelona is argued to be the cause of the significant positive trends found in rainfall amounts. As far as possible linkages between trends on the pluviometric regime and circulation patterns are concerned, a set of cross‐correlations between these indices and the North Atlantic oscillation index has been examined. However, the results are not conclusive, as most of the cross‐correlation coefficients obtained are small and not statistically significant. Copyright © ...