摘要：In Mediterranean climate regions, prolonged periods of unusually dry conditions re-
duce the availability of water resources and affect vegetation cover; while other areas
can be affected by an increase in the number of heavy precipitation events, with an
increase in the flood risk. Issues such as drought and erosive rainfall have been raising
concern about the risks of land degradation and desertification. The main objective
of this paper is to provide an insight of the geographic distribution of extreme precip-
itation events in the Southern region of continental Portugal, as a basis for a future
study of the relationships between extreme rainfall patterns, both spatial and tem-
poral, and desertification processes. The data used in this study are a set of 105
station records with daily precipitation observations for the period 1940–1999. This
60-year period was chosen to optimize data availability across the region, taking into
consideration the quality control analysis performed. Among the numerous indices
of extreme precipitation described in the literature, we selected three of them for an
exploratory analysis: one index representing dry conditions, another one represent-
ing extremely heavy precipitation events and another index representing flood events.
For each of these three indices, yearly trends and decadal space-time patterns are
investigated. The results show no significant trends in the regional extreme indices.
The geostatistical study concluded that the spatial patterns are more continuous in
the last decade than the other ones before. The preliminary results of this study agree
with other similar studies of the same region reported in the literature.
关键词：indices of precipitation extremes; geostatistical approach; southern Portugal.
