Daily precipitation records over mainland Spain and the Balearic Islands

C Ramis,V Homar,R Romero,A Amengual,S Alonso

doi:10.5194/nhess-13-2483-2013

Abstract

Abstract. Understanding the spatial distribution of extreme precipitations is of major interest in order to improve our knowledge of the climate of a region and its relationship with society. These analyses inevitably require the use of directly observed values to account for the actual extreme amounts rather than analyzed gridded values. A study of daily rainfall extremes observed over mainland Spain and the Balearic Islands is performed by using records from 8135 rain gauge stations from the Spanish Weather Agency (AEMET). Results show that the heaviest daily precipitations have been observed mainly on the coastal Mediterranean zone from Gibraltar to the Pyrenees. In particular, a record value of 817 mm was recorded in the Valencia region in 1987. The current map of daily records in Spain, which updates the pioneering work of the Spanish meteorologist Font, shows similar distribution of extreme events but with notably higher amounts. Generalized extreme values distributions fit the Mediterranean and Atlantic rain gauge measurements and shows the different characteristics of the extreme daily precipitations in both regions. We identify the most extreme events (above 500 mm per day) and provide a brief description of a typical meteorological situation in which these damaging events occur. An analysis of the low-level circulation patterns producing such extremes – by means of simple indices such as NAO, WeMOi and IBEI – confirms the relevance of local flows in the generation of either Mediterranean or Atlantic episodes. WeMOi, and even more IBEI, are good discriminants of the region affected by the record precipitation event.

Highlights

Heavy rainfall is the most frequent cause of flooding, far beyond tropical cyclones, monsoonal rain or tidal surges all together (Adhikari et al, 2010)
54 % of the stations in the data base never registered maximum daily amounts above 100 mm and only 1.3 % (i.e. 105 stations) have measured amounts exceeding 300 mm. Most of these 105 extreme values arise on the eastern coastlands of the Iberian Peninsula and eastern Pyrenees, especially concentrated in the Valencia region (Fig. 4)
High values of precipitable water (35 mm) were present over the Mediterranean as it is deduced from the radiosounding launched in Mallorca on 3 November at 12:00 UTC

Summary

Introduction

Heavy rainfall is the most frequent cause of flooding, far beyond tropical cyclones, monsoonal rain or tidal surges all together (Adhikari et al, 2010). Being one of the most hazardous and damaging natural phenomena worldwide, heavy rains cause tremendous losses in terms of human life and property. From 1953 to 2011, 26 exceptional floods have been registered in Spain, with an estimated damage of 8100 million inflation-adjusted USD, 1287 people killed and about 750 000 affected As an example of especially damaging events, it can be mentioned the Biescas (northeastern Spain) flood occurred on 7 August 1996. In such a case, 225 mm fell in 3 h (between 15:00 and 18:00 UTC). In the southern part of France, on 8 and 9 September 2002, a heavy precipitation event was responsible of the most important flooding ever recorded in the Cevennes-Vivarais region. Ramis et al.: Daily precipitation records over mainland Spain and the Balearic Islands

Daily rainfall records

22 Oct 1959 13 Dec 1987 4 Nov 1987 11 Sep 1996 27 Jan 1960 11 Sep 1996

November 1987 matches remarkably well the conceptual

Findings

Conclusions