Turco et al. (2011) Trends in indices of daily precipitation extremes in Catalonia (NE Spain), 1951–2003

Identification

• Journal: Natural hazards and earth system sciences
• Year: 2011
• Date: 2011-12-09
• Authors: Marco Turco, María Carmen Llasat
• DOI: 10.5194/nhess-11-3213-2011

Research Groups

Department of Astronomy and Meteorology, University of Barcelona, Barcelona, Spain

Short Summary

This study quantitatively characterizes daily precipitation extreme indices in Catalonia (NE Spain) from 1951 to 2003, finding no general regional trends but identifying a significant local increase in consecutive dry days (CDD) and specific summer precipitation decreases at the Ebro observatory.

Objective

• To quantitatively characterize the climatology and trends of daily precipitation extreme indices in Catalonia (northeastern Iberian Peninsula) from 1951 to 2003 to understand past climate variability and establish a baseline for regional climate scenarios.

Study Configuration

• Spatial Scale: Catalonia (northeastern Iberian Peninsula), approximately 32 000 km², using a gridded dataset at 0.2° × 0.2° (approximately 20 km × 20 km) horizontal resolution (112 grid points) and two high-quality observatories (Ebro and Fabra).
• Temporal Scale: 1951–2003 (53 years), with analyses performed at annual and seasonal (DJF, MAM, JJA, SON) scales, including running trend analyses with varying time windows (e.g., 30-40 years).

Methodology and Data

• Models used:
  • ETCCDI (Expert Team on Climate Change Detection and Indices) precipitation indices (PRCPTOT, SDII, R95p, RX5DAY, CDD).
  • Jack-knife subsampling technique for estimating sampling error in regional averages.
  • Circular Block Bootstrap procedure for trend analysis and significance assessment, accounting for non-normal distributions and autocorrelated series.
  • Linear regression for trend estimation.
• Data sources:
  • SPAIN02: A high-resolution (0.2° × 0.2°) gridded daily precipitation dataset for the Iberian Peninsula and Balearic Islands, derived from 2756 quality-controlled stations (263 in Catalonia).
  • Daily precipitation series from two high-quality reference stations: Ebro Observatory (40.82° N, 0.49° E, 51 m a.m.s.l.) and Fabra Observatory (41.42° N, 2.12° E, 411 m a.m.s.l.).

Main Results

• No general trends were observed at a regional scale for annual or seasonal regional averaged series of all precipitation indices across all time windows.
• The annual Consecutive Dry Days (CDD) index showed a locally coherent spatial trend pattern: approximately 30% of Catalonia experienced an increase of around 2–3 days per decade.
• Both Ebro and Fabra observatories showed a significant annual CDD increase (Ebro: 2.7 days per decade; Fabra: 2.1 days per decade), primarily attributed to summer contributions.
• For the Ebro observatory in summer, a significant decrease was found in total precipitation (PRCPTOT, around -10 mm per decade) and in the highest precipitation amount in a five-day period (RX5DAY, around -5 mm per decade).
• The sampling error of the SPAIN02 regional average, estimated using a jack-knife technique, was found to be relatively low.
• The Circular Block Bootstrap method was demonstrated to be more reliable for trend significance testing in autocorrelated series compared to the Mann-Kendall test, which can incorrectly neglect significant trends in such cases.

Contributions

• Provides a robust statistical assessment of precipitation extreme variability in Catalonia using Monte-Carlo techniques (jack-knife and bootstrap).
• Implements and makes publicly available a modified Circular Block Bootstrap procedure for trend significance estimation, addressing issues of non-normal distributions and autocorrelation in climate time series.
• Utilizes a new, high-resolution gridded daily precipitation dataset (SPAIN02) alongside high-quality station data for comprehensive regional analysis.
• Establishes a baseline understanding of past precipitation extreme variability in Catalonia, crucial for developing future regional climate scenarios.
• Highlights the importance of robust statistical methods for analyzing climate extremes and the potential for local trends to diverge from regional averages.

Funding

• esTcena project (Exp. 200800050084078), a strategic action from Plan Nacional de I+D+i 2008–2011, funded by the Spanish Ministry of Medio Ambiente y Medio Rural y Marino.

Citation

@article{Turco2011Trends,
  author = {Turco, Marco and Llasat, María Carmen},
  title = {Trends in indices of daily precipitation extremes in Catalonia (NE Spain), 1951–2003},
  journal = {Natural hazards and earth system sciences},
  year = {2011},
  doi = {10.5194/nhess-11-3213-2011},
  url = {https://doi.org/10.5194/nhess-11-3213-2011}
}