Recent trends in daily temperature extremes over northeastern Spain (1960–2006)

S M Vicente-Serrano,A El Kenawy,J I López-Moreno

doi:10.5194/nhess-11-2583-2011

Abstract

Abstract. Spatial and temporal characteristics of extreme temperature events in northeastern Spain have been investigated. The analysis is based on long-term, high-quality, and homogenous daily maximum and minimum temperature of 128 observatories spanning the period from 1960 to 2006. A total of 21 indices were used to assess changes in both the cold and hot tails of the daily temperature distributions. The presence of trends in temperature extremes was assessed by means of the Mann-Kendall test. However, the autocorrelation function (ACF) and a bootstrap methodology were used to account for the influence of serial correlation and cross-correlation on the trend assessment. In general, the observed changes are more prevalent in hot extremes than in cold extremes. This finding can largely be linked to the increase found in the mean maximum temperature during the last few decades. The results indicate a significant increase in the frequency and intensity of most of the hot temperature extremes. An increase in warm nights (TN90p: 3.3 days decade−1), warm days (TX90p: 2.7 days decade−1), tropical nights (TR20: 0.6 days decade−1) and the annual high maximum temperature (TXx: 0.27 °C decade−1) was detected in the 47-yr period. In contrast, most of the indices related to cold temperature extremes (e.g. cold days (TX10p), cold nights (TN10p), very cold days (TN1p), and frost days (FD0)) demonstrated a decreasing but statistically insignificant trend. Although there is no evidence of a long-term trend in cold extremes, significant interdecadal variations were noted. Almost no significant trends in temperature variability indices (e.g. diurnal temperature range (DTR) and growing season length (GSL)) are detected. Spatially, the coastal areas along the Mediterranean Sea and the Cantabrian Sea experienced stronger warming compared with mainland areas. Given that only few earlier studies analyzed observed changes in temperature extremes at fine spatial resolution across the Iberian Peninsula, the results of this work can improve our understanding of climatology of temperature extremes. Also, these findings can have different hydrological, ecological and agricultural implications (e.g. crop yields, energy consumption, land use planning and water resources management).

Highlights

During the second half of the 20th century, the globally averaged 2 m air temperature increased by 0.6 ◦C (Folland et al, 2001)
The autocorrelation function (ACF) results confirm that a majority of the stations do not show significant serial correlation at the lag-1
Characterization of extreme temperature events is important for studies of climate change, hydrological modeling and simulation, and agriculture

Summary

Introduction

During the second half of the 20th century, the globally averaged 2 m air temperature increased by 0.6 ◦C (Folland et al, 2001). This warming was not spatially or temporally uniform. Extreme temperature events can impact many aspects of human life including: mortality, comfort, ecology, agriculture, and hydrology (Schindler, 1997; Ciais et al, 2005; Garcia-Herrera et al, 2005; Patz et al, 2005). The characterization of climate extremes can provide invaluable information for impact assessment studies, those related to hydrological and environmental modeling

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Conclusion