Reg Environ Change DOI 10.1007/s10113-012-0335-0 ORIGINAL STUDY Assessment of climate change simulations over climate zones of Turkey Barıs¸O¨ nol • Yurdanur S. Unal Received: 5 October 2011 / Accepted: 15 July 2012 Ó Springer-Verlag 2012 Abstract Projected climate change over Turkey has been Keywords Climate change Á Regional climate modeling Á analyzed by using the reference (1961–1990) and future Climate of Turkey (2071–2100) climate simulations produced by ICTP-Reg- CM3. Since examining Turkey as a single region could be misleading due to the existence of complex topography and Introduction different climatic regions, Turkey has been separated into seven climatic regions to evaluate the surface temperature Sensitivity of global mean variables such as temperature and precipitation changes. Comparison of the reference and precipitation to greenhouse forcing shows significant simulation with observations was made spatially by using a disagreement between global climate models. However, 15 monthly gridded data set and area-averaged surface data climate models used in IPCC 4th assessment reports show compiled from 114 meteorological stations for each cli- remarkable agreement on dry conditions, which will matic region of Turkey. In the future simulation, warming dominate the eastern Mediterranean region (Wang 2005). over Turkey’s climatic regions is in the range of 2–5 °C. In addition, global future climate projections reveal that Summer warming over western regions of Turkey is 3 °C Mediterranean region is one of the most responsive regions higher than the winter warming. During winter, in the to the global warming (Giorgi 2006). future simulation, precipitation decreases very significantly In Giorgi’s study (2006), a Regional Climate Change over southeastern Turkey (24 %), which covers most of the Index (RCCI) has been developed using 20 global climate upstream of Euphrates and Tigris river basin. This pro- models with three IPCC emission scenarios to define the jected decrease could be a major source of concern for vulnerability of the regions to climate change. National Turkey and the neighboring countries. Our results indicate Climate Change Index and climate change population that a significant increase (48 %) in the autumn season index have also been developed by Diffenbaugh et al. precipitation is simulated over southeastern Turkey, which (2007) using RCCI to describe socio-climatic exposure in may help to offset the winter deficit and therefore reduce future for all countries. His analysis indicates that Turkey the net change during the annual cycle. is more vulnerable to socio-economic affects than the other Mediterranean countries, especially when its future popu- lation is considered. These studies suggest that regional climate model simulations are necessary over the Eastern Mediterranean (EM) region, especially concentrating on Electronic supplementary material The online version of this Turkey, to provide detailed information about the climate article (doi:10.1007/s10113-012-0335-0) contains supplementary material, which is available to authorized users. in the twenty-first century. Regional changes in climate will most directly affect B. O¨ nol (&) Á Y. S. Unal human activities, and thus, predictions of regional climate Aeronautics and Astronautics Faculty, Meteorological change are of great practical and scientific interest. We Engineering, Istanbul Technical University, Maslak, Istanbul, Turkey completed two sets of multi-decadal simulations over the e-mail: [email protected] EM domain with the regional climate model RegCM3 123 B. O¨ nol, Y. S. Unal (Giorgi et al. 1993a, b; Giorgi and Shields 1999) nested The climate of Turkey is characterized as Mediterra- within the NASA Finite Volume General Circulation Model nean. The topography and land-use of Turkey are very (fvGCM) for the period of 1961–1990 and for the period of diverse, and therefore, large-scale atmospheric motions are 2071–2100 under SRES A2 emission scenario. Although mainly affected by complex surface conditions. The O¨ nol and Semazzi (2009) present the model validation and mountain ranges running parallel to the coasts of the analysis for the entire domain of this simulation, their study Mediterranean Sea and the Black Sea result in significant does not include a detailed analysis for Turkey. However, it climate variability between northern and southern parts of is necessary to do comprehensive analyses of the future the mountains. Comparison of RegCM simulations with projections for Turkey which has very diverse climatic surface observations in Evans et al. (2004) reveals that the regions caused by complex topography and land sea dis- model produces excessive precipitation over the Eastern tribution. In this study, we have analyzed regional climate Black Sea Mountains. However, Hahmann et al. (2008) model outputs produced by RegCM version 3, which is used WRF and MM5 with higher resolution of 15-km and originally developed by Giorgi et al. (1993a, b) and later simulated the month of January for years between 2001 and improved by Giorgi and Shields (1999) and Pal et al. (2000, 2006 by perfect boundary conditions (NCEP re-analysis). 2007). Relatively high resolution of 30-km is implemented They found that precipitation field is consistent with the to better resolve the complex topography of Turkey. station observations over the Mediterranean coast. Along Regional climate modeling studies concerning the EM the Aegean Sea coast, mountains are located perpendicular region (Krichak et al. 2011, 2007; Hadjinicolaou et al. to the coastline, which permits penetration of the westerly 2011; Giannakopoulos et al. 2011; Gao and Giorgi 2008; flow to inland areas. However, climate of the regions close Alpert et al. 2004) project that the future climate change to the Aegean Sea coastline still differs from the inland over Turkey shows regional variations even though they do climate due to the elevated topography. During winter, not include the whole of Turkey in their domain. It is noted Turkey is under the influence of airflow with a polar origin. that there are significant variations of temperature and On the other hand, during autumn and summer, tropical precipitation from south to north and from east to west in airflow dominates the region. Turkey. Therefore, it is necessary to study the future cli- The nature of precipitation is an important hydrological mate projections regionally in order to analyze the regional factor, especially over the eastern Anatolia, since the differences and the origin of changes. Recently, projected headwaters of cross-boundary river systems of Turkey are changes on water resources in Turkey and the surrounding located within the region. From April through June, regions have been investigated by using RCMs with snowmelt contributes around half of the annual runoff. One Chenoweth et al. (2011) and Hemming et al. (2010). These of the most significant potential impacts of climate vari- studies also pointed out that there are diverse precipitation ability and change may be alterations in the regional regime changes between northern (increase) and southern hydrological cycle and subsequent changes in river dis- (decrease) Turkey for SRES A1B scenario simulated by charge. Change of precipitation regime within this basin HadCM3. However, in both studies, area-averaged calcu- will have significant consequences in the rivers systems of lations have been utilized for all of Turkey to determine Euphrates and Tigris, which concern not only Turkey but water availability. In the study by Chenoweth et al. (2011), also Syria and Iraq. Sustainability of fresh water resources they used PRECIS model with 25-km horizontal resolution in the future could be the main driving force for conflicts for the period of 2070–2099. Their results show that pro- among these countries. jected annual precipitation decreases in the range of Turkey occupies an area of 783,562 km2. It is encircled 20–100 % over southern and western Turkey and increases by the Aegean Sea to the west, the Black Sea to the north 5–15 % over northeastern Turkey. Hemming et al. (2010) and the Mediterranean Sea to the south, and the Thrace and also reaches quite similar results (but of lesser magnitude) Anatolia parts of Turkey are separated by the Sea of on annual precipitation change using ensemble analysis of Marmara. The geographic location of Turkey, as well as GCM (17 member) and RCM (5 member, 50-km horizontal the topographic barriers, shapes the climate of Turkey and resolution) simulations for the 2021–2050 period. In results in very distinct climatic regions. Therefore, it is addition, MM5 simulations (27-km) driven by CCSM3 for necessary to evaluate the climate projections in each dis- the first and last 5 years of the twenty-first century indicate tinct region separately. more than 100 % precipitation change over southern In this paper, we examine the imprints of reference and (decrease) and northeastern (increase) coasts of Turkey for scenario simulations in seven climate zones over Turkey all seasons except summer (Evans 2010). Analysis of defined by Unal et al. (2003) using the temperature and super-high-resolution GCM (20-km) simulations by Kitoh precipitation variability. In Sect. ‘‘Methods and data,’’ we et al. (2008) also agrees with previous studies on annual introduce the methodology of the paper and the data set precipitation tendencies over Turkey. used. In Sect. ‘‘Results,’’ temperature and precipitation 123 Assessment of climate change simulations simulations for the period 1961–1990 called RF and period RF and A2 simulations for the larger model domain of 2071–2100 called A2 are presented. The final section 28°N–50°N, 10°E–50°E has been analyzed and discussed includes conclusion and discussion of our results. in O¨ nol and Semazzi (2009). Here, we concentrate on the smaller domain (36°N–42°N; 26°E–45°E) results of RF and A2 simulations. In these simulations, horizontal reso- Methods and data lution is 30 km and vertical resolution is 18 sigma levels. Land cover and topography generated by RegCM3 over The primary vehicle of our investigation is the RegCM3 Turkey is presented in Fig.