Simulated and observed air temperature trends in the eastern Adriatic

Climate predictions of air temperature in coastal regions represent a great challenge due to the complex interactions among the atmosphere, sea, and land. With approximately 1,200 islands, the Adriatic is a region with a strong land-sea contrast, land-atmosphere feedback, and intense air-sea interaction. Because the Mediterranean has been regarded as a "hot spot" for climate change, regional climate models can be used to provide insight into a more realistic representation of small-scale weather and climate structure and variability. This advantage is due to the better representation of complex topography, developed coastlines, and land-sea contrasts, which are important for investigating air temperature trends. The use of regional climate models together with high-resolution reanalyses and observations in assessments of climate variability and climate change is highly valuable for understanding climate processes at regional scales. The present study focused on air temperature and its trends calculated from measurements and simulated by eight regional climate models from the EURO-CORDEX database; these data were represented by UERRA reanalyses and E-OBS gridded data. In the evaluation period (1989-2008), the models' RMSEs were fairly small, in the range 0.5-1.5 degrees C, compared to the historical period (1961-2005), with RMSEs greater than 1.75 degrees C. However, the models showed small absolute trend differences (up to 0.12 degrees C center dot decade(-1) for the historical period). The ensemble means in both periods showed an accuracy improvement of 15-20% compared to the individual models. The models exhibited more success in terms of representing the main statistics and variability of the air temperature structure than in reproducing the temperature trends over 45 years, especially in the northern Adriatic, where there is complex coastal topography and significant seasonal variability in the wind regime. The reanalyses well represented temperature structure but showed less success in explaining the temperature trends than the results from the measured data.