The future climate in Portugal: high-resolution projections using WRF model and EURO-CORDEX multi-model ensembles

14:00 Wednesday 29 May

OC134

Room S7

 

Pedro M.M. Soares (Portugal) 1; Rita M. Cardoso (Portugal) 1; Daniela C.A. Lima (Portugal) 1

1 - Instituto Dom Luiz, Faculdade de Ciências, Universidade de Lisboa

Portugal, which is located in the west limit of the Mediterranean subtropics, is a small region with a complex orography with large temperature and precipitation gradients and interannual variability. In this study, the newer and higher resolution regional climate simulations, covering Portugal, are evaluated in present climate and used to investigate the temperature and rainfall projections for the mid and the end of the 21st century, following the RCP4.5 and RCP8.5 emission scenarios.

The EURO-CORDEX historical simulations, at 0.11o and at 0.44o resolution, are evaluated against observations, which allows the assembly of four multi-model ensembles. An extra simulation, at even higher resolution (9km) with WRF is also analyzed. In present climate, the models are able to describe the temperatures and precipitation temporal and spatial patterns as well its distributions. Although for precipitation there is a large spread and an overestimation of larger rainfall quantiles.

The multi-model ensembles show that selecting the best performing models adds quality to the overall representation of all the variables. The high-resolution simulations augment the spatial details of precipitation, but objectively do not seem to add value with respect to the coarse resolution. Regarding the RCP8.5 scenario, WRF and the multi-model ensembles consistently predict important losses of precipitation in Portugal in spring, summer and autumn, ranging from -10% and -50%. For all seasons, the changes are more severe in the southern basins. The precipitation distributions show, for all models, important reductions of the contribution from low to moderate/high precipitation bins and augments of days with strong rainfall.

Furthermore, a prominent growth of high-ranking percentiles is predicted reaching values over 70% in some regions. Generally, the changes associated with the RCP4.5 scenario have the same signal and features, but with smaller magnitudes. For temperatures all multi-model ensembles project significant increases of seasonal average values, that in summer and autumn may reach 6oC of warming for the northeast of the mainland. More importantly, a very sharp rise of the number, mean duration and maximum duration for the heatwaves is projected. For example, the longest heatwaves may last for more 50 days by the end of the century.

Acknowledgements

The authors wish to acknowledge SOLAR (PTDC/GEOMET/7078/2014) and FCT UID/GEO/50019/ 2013 (Instituto Dom Luiz) projects.