10th International Congress of the Hellenic Geographical Society, Thessaloniki 23 October 2014 A high resolution regional climate simulation for Greece for the period : Evaluation and future projections Prodromos Zanis Department of Meteorology and Climatology, School of Geology, AUTH

Acknowledgments to my co-authors: Katragkou E., Ntogras C., Feidas H. Department of Meteorology and Climatology, School of Geology, AUTH Marougianni G, Melas D. Laboratory of Atmospheric Physics, Physics Department, AUTH Anadranistakis E. Hellenic National Meteorological Service The work was carried out in the framework of the GEOCLIMA project ( through the Operational Program “Competitiveness and Entrepreneurship” of the National Strategic Reference Framework (NSRF) – Research Funding Program COOPERATION 2009.

Climate modeling Coupled AOGCMs are the most advanced tools today available for climate simulation The resolution of present day AOGCMs (100 – 300 km) is still too coarse to provide fine scale regional climate information useful for impact studies

Regional Climate Modeling: Technique and Strategy Technique: A “Regional Climate Model” (RCM) is “nested” within a GCM in order to increase the resolution of a climate simulation. –Initial conditions (IC) and lateral boundary conditions (LBC) for the RCM are obtained from the GCM. Strategy: The GCM is used to simulate the response of the general circulation to large scale forcings, while the RCM is used to simulate the effect of sub-GCM- grid scale forcings and to provide fine scale regional information –The RCM is intended to only enhance the GCM information Technique inherited from NWP

Mean precipitation climatology Obs GGDB Obs CRU 50 km RCM200 km GCM11 km RCM (Tselioudis et al., Int. J. Clim., 2011)

Crete Peloponnese Rhodes Thrace Macedonia Aegean sea Ionian sea Thessaly Epirus Pindus mountains Central Greece Model domain Grid resolution 10 km x 10 km simulation period Lateral boundary conditions: RegCM3 (25 km x 25 km) forced by ECHAM5 under A1B IPCC scenario (4.5 TB). Use of the GRID-HELLAS platform

a) b) c)d) e) Mean annual near-surface temperature ( ) for a) HNMS stations, b) E-obs, c) RCM10, d) RCM25 and e) the forcing GCM ECHAM5

a)b) c) d) e) Annual precipitation sum ( ) for a) HNMS stations, b) E-obs, c) RCM10, d) RCM25 and e) the forcing GCM ECHAM5

a)b) c)d) Mean annual bias in near surface temperature ( 0 C) and precipitation (mm) over the period for RCM10 (a and c) and for RCM25 (b and d)

a) b) c)d) e)f) Change between and as well as between and for the annual mean (a and b), maximum (c and d) and minimum (e and f) near-surface temperature ( 0 C) based on the RCM10 simulation

a) b) c) d) Annual precipitation change in (%) and in (mm/day) between and (a and c) as well as between and (b and d) based on the RCM10 simulation

a)b) c)d) Seasonal mean near surface temperature change ( 0 C) between and for a) winter, b) spring, c) summer and d) autumn based on the RCM10 simulation

a)b) c)d) Seasonal mean precipitation change (mm/day) between and for a) winter, b) spring, c) summer and d) autumn based on the RCM10 simulation

Indices 2 a)b) c)d) e)f) Annual change between and as well as between and for the number of hot days with Tmax>35 o C (a and b), for the number of warm days with Tmin>20 o C (c and d), as well as the number of night frost days with Tmin<0 o C (e and f) based on the RCM10 simulation

a)b) c)d) Annual change between and as well as between and for dry spell days (a and b) and the growing season days (c and d) based on the RCM10 simulation

Key points - conclusions A transient high resolution (10 km x 10 km) simulation (RCM10) was carried out with RegCM3 over the period that constitutes a climate simulation, for the first to our knowledge, with such a high resolution for Greece. A station-based evaluation showed that the mean annual bias in near surface temperature is reduced in RCM10 compared to RCM25 and the bias in annual precipitation is also reduced over mountain regions. In the early future period ( ), annual temperature increases mostly over land by less than 1.8 ο C and precipitation change ranges between ±15%, being mostly negative in the southern part of the domain. At the end of the century ( ), the mean annual temperature increases by about 3.4 ο C to 4.2 οC over land and by 2.6 ο C to 3.4 ο C over the sea while precipitation decrease by 10% to 40% with a positive gradient from the north to the south. Summer presents the largest future increase in mean near surface temperature over the Greek mainland while winter and spring show the largest decreases in precipitation rate. The number of hot days, warm nights, night frost days length of the growing season and continuous dry spell days are projected to increase slightly in the near future period but largely and consistently in the late 21st century future period in accordance with the generally warmer and drier climate projected from the RCM10 simulation for Greece.

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