Near-future climate change over Europe with focus on Croatia in an ensemble of regional climate model simulations

Abstract

The RegCM climate model was used at a 35 km resolution to downscale the 3-member global ECHAM5/MPI-OM ensemble based on the IPCC A2 scenario covering the EuropeanMediterranean domain. Within the reference climate (1961−1990), the model high 2 m temperatures (T2m) were reduced and low temperatures were increased relative to verification in a large portion of the domain. Precipitation was underestimated in summer over the Mediterranean region but was overestimated over western Europe in winter, probably due to excessive westerlies in the global model. When RegCM was forced by ERA-40, the dominant errors in the summer T2m appear to be genuine RegCM errors, but a large fraction of errors in winter precipitation was imported from the lateral boundaries. In the near future (2011−2040), the summer T2m is projected to increase by +1.8°C over southwest Europe. The simulated change in precipitation is small and is significant only in regions around the Mediterranean. The wetter north and drier south, a major feature in projections of the European winter climate in the late 21st century, is not predicted for the near future. Similarly, summer drying is confined to western Europe in contrast to nearly continental scale drying observed in projections of the late 21st century. This finding may influence the approaches for adaptation to climate change in the first half and at the end of this century. The effects of downscaling at small scales are analysed for the case of Croatia. The spatial distribution of the number of days with extreme T2m and precipitation in RegCM is consistent with observations. However, this metric is generally underestimated, indicating that over complex orography, even higher horizontal resolution is needed to better resolve climate extremes.

INTRODUCTION The road towards RegCM4 F. Giorgi1,*, R. O. Anyah2

“…Gao et al (2012), in particular, completed a 1950-2100 scenario simulation, showing that the temperature change signal is mostly determined by large-scale conditions, while the precipitation change signal is strongly modulated by fine-scale topographical forcing. Similar conclusions, although with smaller signals, are found in the 35 km grid spacing near term climate scenario ex periments over a European domain by Branković et al (2012). They also focused on the simulation of extremes, showing that a very high resolution is indeed needed to reproduce observed statistics of the most intense precipitation events.…”

Maximum temperatures over Slovenia and their relationship with atmospheric circulation patterns

“…Significant progresses have been made on the climate projections for the Mediterranean region (Branković et al 2012, Vautard et al 2013, Lionello et al 2014. Study of Giorgi (2006) showed that the most responsive region to clim atic change is Mediterranean followed by the North Eastern European regions.…”

Performance of RegCM4 simulations over Croatia and adjacent climate regions

“…Figure 1f,j with h,l). Such an underestimation of summer precipitation over southern Europe is found to be a persistent deficiency in several generations of RCMs (Hagemann et al ., 2004; Kotlarski et al ., 2014; Ceglar et al ., 2015; Prein et al ., 2015a; Giot et al ., 2016) and in particular over the Adriatic region (Branković et al ., 2012, 2013). The resolution increase yields a reduction of precipitation errors over the northern parts of CRO in the ERA‐Interim runs; however, this is less obvious in simulations when RegCM4 is forced by GCMs.…”