INTERNATIONAL JOURNAL OF CLIMATOLOGY
Int. J. Climatol. 18: 541–560 (1998)
A 30-YEAR (1964–1993) DAILY RAINFALL DATA BASE FOR THE
SPANISH MEDITERRANEAN REGIONS: FIRST EXPLORATORY
STUDY
R. ROMERO
a
, J.A. GUIJARRO
b
, C. RAMIS
a,
* and S. ALONSO
a
a
Meteorology Group, Departament de Fı ´sica, Uniersitat de les Illes Balears, Palma de Mallorca, Spain
b
Instituto Nacional de Meteorologı ´a, Centro Meteorolo ´gico de Baleares, Palma de Mallorca, Spain
Receied 6 June 1997
Reised 17 Noember 1997
Accepted 20 Noember 1997
ABSTRACT
A dense daily precipitation data base, extending from 1964 to 1993, has been created for the Mediterranean regions
of Spain. It is composed of complete and homogeneous series at 410 raingauge stations (347 in the coastal fringe of
peninsular Spain, and 63 in the Balearic Islands). The region offers an interesting scenario for mesoclimatological
studies on time and spatial rainfall variability: geomorphologically, it is characterized by important coastal relief units
and complex distribution of sea and land masses, leading to different exposures to the rain-bearing maritime winds;
climatically, the western Mediterranean is subject to strong seasonal variability, since it is a transition zone between
the midlatitude low pressure belt and the subtropical highs as a result of its latitude (between 36° and 44° N). In this
study, we exploit the data base and present a first pluviometric characterization of the area by means of yearly and
seasonal mean products. The results reveal clear and coherent spatial patterns that we interpret, based on typical
storm tracks and land, sea, and relief distributions. In addition, a partition of the 30-year period into three decades
(1964–1973, 1974–1983, 1984–1993) has been considered in order to assess the possible existence of any trend. A
successive drying of the most sensitive areas to the winter Atlantic depressions (western Catalonia, and central and
west Andalucı ´a) is observed. In contrast, the second analysed decade is appreciably drier than the other two in the
areas more dependent on the Mediterranean disturbances. The occurrence of anomalous autumns being the most
responsible. This fact emphasizes the fundamental importance of the autumn season for the pluviometric balance of
the considered area, especially in its eastern part where the major amount of precipitation during this season is
produced by convective systems. © 1998 Royal Meteorological Society.
KEY WORDS: Western Mediterranean region; Spain; rainfall characterization techniques; climate variables; interpolation; rain
days; extreme rainfall; wet/dry periods
1. INTRODUCTION
The western Mediterranean region is defined as the portion of the Mediterranean Sea enclosed by Spain,
France, Corsica, Sardinia and north Africa, and the surrounding lands (Meteorological Office, 1962).
That part of the Mediterranean Sea is surrounded by important mountain ranges with notable foothills
reaching the coast line. Figure 1 shows a smoothed orography of the region. The most relevant and
known ranges are the Atlas mountains in north Africa, Penibetic and Iberic Systems in Spain, Pyrenees
between Spain and France, Central Massif in France, and Alps between France and Italy. Even the
islands, regardless of their small size, emerge abruptly from the sea (Balearic Islands, Corsica, Sardinia,
Figure 1). The topography configures the western Mediterranean as a closed basin isolated from other
regions except through the valleys and narrow straits; for example the Gulf of Lyons area, where Atlantic
* Correspondence to: Grup de Meteorologia, Departament de Fı ´sica, Universitat de les Illes Baleares, 07071 Palma de Mallorca,
Spain. e-mail:dfscrn0@ps.uib.es
Contract grant sponsor: CICYT; Contract grant number: CLI95-1846
CCC 0899–8418/98/050541 – 20$17.50
© 1998 Royal Meteorological Society