High-resolution decadal climate predictions of temperature in the Iberian Peninsula

The Decadal Climate Prediction (DCP) attempts to fulfil the need for near-term climate information for decision-making in different sectors of the society. Previous studies have detected a trend towards warmer conditions during the 20th century in the Mediterranean regions, and it is expected that this continues during the ongoing 21th century. Thus, reliable predictions of temperature will play an essential role in the development of adaptation and mitigation strategies to the potential impacts of climate change in these regions.

The aim of this study is to analyse a set of high-resolution decadal climate predictions of temperature in the Iberian Peninsula (IP). These simulations have been produced through a dynamical downscaling approach by using the Weather Research Forecasting (WRF) model version 3.9.1.1 with the initial and boundary information provided by the Decadal Prediction Large Ensemble (DPLE). The DPLE encompasses a set of decadal climate experiments initialised every year in November from 1954 to 2015 which were carried out with the Community Earth System Model (CESM) at NCAR. For each initialisation date, an ensemble of 40 members was generated by randomly perturbing the initial atmospheric conditions. In this study, the subset of DPLE experiments initialised every year from 1987 to 1999 (13 decades) for 3 members of the ensemble has been dynamically downscaled. The dynamical downscaling simulations have been conducted in two nested domains by using a one-way approach. A domain covers the EUROCORDEX region with resolution around 50 km and another, finer, spans the IP with resolution about 10 km. Prior to performing any simulation, the input DPLE data have been corrected by removing the mean lead time-dependent drift with ERA-Interim as a reference dataset.

The prediction skill of the regionalised experiments have been evaluated against the Iberia01 observational dataset. In order to explore the dependence of the prediction skill on the lead time, these decadal predictions have been analysed in several forecast ranges. The results will help to understand the role of regionalised DCPs in those regions where the resolution provided by global models is too coarse.

Keywords: temperature, Weather Research and Forecasting Model, Iberian Peninsula, dynamical downscaling, Decadal Prediction Large Ensemble.

Acknowledgments: J. J. Rosa-Cánovas acknowledges the Spanish Ministry of Science, Innovation and Universities for the predoctoral fellowship (grant code: PRE2018-083921). This research has been carried out in the framework of the projects CGL2017-89836-R, funded by the Spanish Ministry of Economy and Competitiveness with additional FEDER funds, B-RNM-336-UGR18, funded by FEDER / Junta de Andalucía - Consejería de Economía y Conocimiento, and P20_00035, funded by FEDER/Junta de Andalucía-Consejería de Transformación Económica, Industria, Conocimiento y Universidades and the Spanish Ministry of Science and Innovation (project LifeWatch-2019-10-UGR-01).