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Öğe Analysis of observed variability and trends in numbers of frost days in Turkey for the period 1950-2010(Wiley, 2012) Erlat, Ecmel; Turkes, MuratThis study examines the climatology of annual frost days, and analyses the size and behaviour of the long-term variability and trends in annual numbers of frost day at the 72 stations over Turkey from 1950 to 2010. The main results are summarized as follows: (1) The annual number of frost days has evidently decreased at most of the stations with some observed regional differences, (2) The decreasing trends are largest over the Eastern Anatolia, the Marmara regions and along the Mediterranean coastline. The meteorological stations located in the continental northeast and the easternmost parts of the Anatolian Peninsula, including Ardahan, Igdir and Van, show a negative linear trend with a rate of four days per decade, (3) As in other regions of the Earth, changes in number of frost days are very likely associated with changes in minimum air temperatures and increasing growing season lengths in Turkey, (4) The decreasing trends in number of frost days also indicated considerable decadal-scale variability. This variability is very likely attributable to the large-scale atmospheric circulation and atmospheric oscillations such as the Arctic Oscillation (AO) or North Atlantic Oscillation (NAO) and the North Sea-Caspian Pattern, (5) Consequently, the long-winter (DJFM) composites of number of frost days were examined for extreme phases of the AO index during the period 19502010 in order to assess the influence of atmospheric oscillations on year-to-year variability in number of frost days. According to the Cramer's tk test, winter number of frost days tended to increase significantly during the high (positive) index AO phase, while they tended to decrease significantly during the low (negative) index AO phase. These relationships are statistically significant at the 1% level at the majority of stations. Copyright (c) 2011 Royal Meteorological SocietyÖğe Clustering current climate regions of Turkey by using a multivariate statistical method(Springer Wien, 2013) Iyigun, Cem; Turkes, Murat; Batmaz, Inci; Yozgatligil, Ceylan; Purutcuoglu, Vilda; Koc, Elcin Kartal; Ozturk, Muhammed Z.In this study, the hierarchical clustering technique, called Ward method, was applied for grouping common features of air temperature series, precipitation total and relative humidity series of 244 stations in Turkey. Results of clustering exhibited the impact of physical geographical features of Turkey, such as topography, orography, land-sea distribution and the high Anatolian peninsula on the geographical variability. Based on the monthly series of nine climatological observations recorded for the period of 1970-2010, 12 and 14 clusters of climate zones are determined. However, from the comparative analyses, it is decided that 14 clusters represent the climate of Turkey more realistically. These clusters are named as (1) Dry Summer Subtropical Semihumid Coastal Aegean Region; (2) Dry-Subhumid Mid-Western Anatolia Region; (3 and 4) Dry Summer Subtropical Humid Coastal Mediterranean region [(3) West coast Mediterranean and (4) Eastern Mediterranean sub-regions]; (5) Semihumid Eastern Marmara Transition Sub-region; (6) Dry Summer Subtropical Semihumid/Semiarid Continental Mediterranean region; (7) Semihumid Cold Continental Eastern Anatolia region; (8) Dry-subhumid/Semiarid Continental Central Anatolia Region; (9 and 10) Mid-latitude Humid Temperate Coastal Black Sea Region [(9) West Coast Black Sea and (10) East Coast Black Sea sub-regions]; (11) Semihumid Western Marmara Transition Sub-region; (12) Semihumid Continental Central to Eastern Anatolia Sub-region; (13) Rainy Summer Semihumid Cold Continental Northeastern Anatolia Sub-region; and (14) Semihumid Continental Mediterranean to Eastern Anatolia Transition Sub-region. We believe that this study can be considered as a reference for the other climate-related researches of Turkey, and can be useful for the detection of Turkish climate regions, which are obtained by a long-term time course dataset having many meteorological variables.Öğe Contemporary surface wind climatology of Turkey(Springer Wien, 2013) Sahin, Sinan; Turkes, MuratThe aim of this study was to examine the climatological characteristics of boundary layer gradient winds in Turkey in detail. In the study, monthly average wind speed (V (m)) data measured at 267 stations for the 16 directions, prevailing wind direction (V (p)), and station pressure (P (s)) data measured at 174 stations during the period 1970-2008 by the Turkish Meteorological Service (TMS) were used. The data were provided by the TMS. To attain the aim of the study, wind patterns of midseason months representing the seasonal wind distributions were used, and surface wind formations were examined through calculation of divergent and rotational components of the average wind rate. Besides, it was aimed at explaining the relationships between sea level pressure (SLP) patterns and wind formations. The patterns of midseason months were examined via the Principal Component Analysis (PCA). In accordance with V (m) data, it is seen that air flows in Turkey generally tend to orientate radially from west to east. Climatologically, the strongest prevailing winds in Turkey blow during the summer months, while the weakest winds blow during the autumn months. V (m) and V (p) distributions show a parallelism (i.e., wind gradient) in the months during which temperature differences between land and sea are high due to the differences in their specific heat values. The distributions of V (m) and V (p) values vary considerably in spring and autumn months during which temperature differences are relatively lower. According to the PCA results, the first two components represent the strong wind areas in Turkey. These components presumably explain the existence of coherent wind formation areas, which display different characteristics due to regional physical geographical factors and processes (e.g., orography, altitude, exposure, land-sea distribution, surface mechanical and thermodynamic modifications of the air masses and air flows, etc.) in addition to the direct effect of different synoptic-scale pressure and circulation conditions.Öğe Depositional Characteristics of Carbonate-Cemented Fossil Eolian Sand Dunes: Bozcaada Island, Turkey(Coastal Education & Research Foundation, 2013) Erginal, Ahmet Evren; Ekinci, Yunus Levent; Demirci, Alper; Avcioglu, Mustafa; Ozturk, Muhammed Zeynel; Turkes, Murat; Yiğitbaş, ErdinçErginal, A.E.; Ekinci, Y.L.; Demirci, A.; Avcioglu, M.; Ozturk, M.Z.; Turkes M., and Yigitbas, E., 2013. Depositional characteristics of carbonate-cemented fossil eolian sand dunes: Bozcaada Island, Turkey. Journal of Coastal Research, 29(1), 78-85. Coconut Creek (Florida), ISSN 0749-0208. Coastal eolianite on the south coast of Bozcaada Island, Turkey, was investigated by field observations, petrographic and climatological examinations, and electrical resistivity tomography data. The 4- to 7-m-thick eolianite, including rhizolith morphotypes characterized by root tubules and bifurcated root casts, demonstrates dune-sand accumulation during the Upper Pleistocene. Our results showed that paleowind drift and recent windblown sand drift on the island are similar. The dune sands exhibit various cement types formed of calcite and aragonite, such as micrite encrustations, meniscus and gravitational cements, and in particular, void fills. Dune-sand accumulation took place on the truncated surface of Miocene deposits. Geophysical data showed the existence of large weathered cavities within the eolianite and a high-angle normal fault, which displaces the eolianite, together with the underlying Miocene unit.Öğe Geomorphological investigation of the excavation-induced Dundar landslide, Bursa, Turkey(Taylor & Francis Ltd, 2008) Erginal, Ahmet Evren; Turkes, Murat; Ertek, T. Ahmet; Baba, Alper; Bayrakdar, CihanThis paper discusses the occurrence and development of the excavation-induce deep-seated landslide, which took place near Dundar village, located west of Orhaneli town in northwestern Turkey. The event occurred in the Bursa-Orhaneli lignite field, which has been actively operating since 1979. Due to undermining of a gently inclined slope (10 degrees) to extract a coal seam, primary tension cracks, which were precursors of the movement, were first observed in the northern head area in mid- to late October 2003. This movement happened simultaneously with precipitation that was significantly above long-term average measured at a nearby climatology station (Keles). This precipitation amount is characterized statistically by a significant standardized anomaly of 1.6. The majority of the monthly precipitation total in October 2003, which mainly consisted of rain showers and thunderstorms, occurred in the last week of the month. By April 2004, rotational failure continued intermittently. After a relatively wet (rainy and snowy) period from January 2004 to April 2004, the main rotational slump occurred in late April 2004, causing the entire destruction of Dundar village's cemetery. Daily climatic and synoptic meteorological data have proved that heavy showers in late April may had triggered the last slump by producing rain showers of 19.3 mm and 19.9 mm daily total on 27 and 28 April 2004, respectively. Field observations carried out along the main head scarp have shown that the slope failure was facilitated by a pre-existing normal fault with an east- west direction and 80 degrees dip. Grain-size analysis showed that the failure occurred on clayey silt, which forms 55% of the slip surface material. Based on the evidence from X-ray fluorescence and energy dispersive X-ray spectroscopy results, smectite-type clay - a product of the chemical weathering of tuff - was the main constituent of the slip surface material. The landslide occurred over an area of 600 m x 650 m with a total volume of 8775 000 m(3). Approximately 28 hectares of farm land were entirely destroyed and the excavated coal seam was buried. The mining operation was moved to 100 m north of the landslide area near Gumuspinar village. From morphological evidence, it is concluded that excavation activities caused the failure to extend in more than one direction as an enlarging sliding mechanism; this produced a high landslide risk for Gumuspinar village, where the most significant normal fault with a 75 m vertical displacement in a coal-bearing sequence is found in the lignite field.Öğe Observed changes and trends in numbers of summer and tropical days, and the 2010 hot summer in Turkey(Wiley, 2013) Erlat, Ecmel; Turkes, MuratLong-term variability and trends of the annual numbers of summer and tropical days were investigated by using nonlinear (monotonic) and linear trend detection tests for the period 1950-2010 for 97 meteorological stations of Turkey. The results suggest that the numbers of both summer and tropical days indicate a general increasing tendency in Turkey. For the study period, statistically significant increasing trends for summer (tropical) days are detected at 64 (71) stations, of which 51 (58) of these positive trends are significant at the 0.01 significance level. Two periods of changes in summer and tropical days are identified: in the 1950-1975 sub-period with an episode of slight cooling, the annual number of summer and tropical days decreases, whereas in the sub-period of 1976-2010 with an episode of significant increasing trend, the annual number of summer and tropical days increases. The summer of 2010 was exceptional for the number of summer and tropical days at most of the stations in Turkey. Normalized anomalies of summer (tropical) days at 2010 were larger than three standard deviations with respect to 1961-1990 normal at 27 (43) stations. The largest positive anomalies are observed in the northeastern Anatolia sub-region. This increasing trend has significant impacts on agriculture, energy, tourism and natural ecosystems (e.g., forest fires) in Turkey. Copyright (c) 2012 Royal Meteorological SocietyÖğe Projecting climate change, drought conditions and crop productivity in Turkey(Inter-Research, 2012) Sen, Burak; Topcu, Sevilay; Turkes, Murat; Sen, Baha; Warner, Jeoren F.This paper focuses on the evaluation of regional climate model simulation for Turkey for the 21st century. A regional climate model, ICTP-RegCM3, with 20 km horizontal resolution, is used to downscale the reference and future climate scenario (IPCC-A2) simulations. Characteristics of droughts as well as the crop growth and yields of first- and second-crop corn are then calculated and simulated based on the data produced. The model projects an increase in air temperature of 5 to 7 degrees C during the summer season over the west and an increase of 3.5 degrees C for the winter season for the eastern part of the country. Precipitation is predicted to be 40% less in the southwest, although it may increase by 25% in the eastern part of the Black Sea region and north eastern Turkey. Trends in drought intensity and crop growth are related to climate changes. The results suggest more frequent, intense and long-lasting droughts in the country particularly along the western and southern coasts under future climate conditions. A shift of climate classes towards drier conditions is also projected for the western, southern and central regions during the 21st century. Evaluating the role of the climate change trends in crop production reveals significant decreases in yield and shortened growth seasons for first-and second-crop corn, a likely result of high temperatures and water stresses. In addition to rising temperatures and declining precipitation, increasing frequency, severity and duration of drought events may significantly affect food production and socio-economic conditions in Turkey. Our results may help policy makers and relevant sectors to implement appropriate and timely measures to cope with climate-change-induced droughts and their effects in the future.Öğe Shallow and deep-seated regolith slides on deforested slopes in Canakkale, NW Turkey(Elsevier, 2013) Ekinci, Yunus Levent; Turkes, Murat; Demirci, Alper; Erginal, Ahmet EvrenThis study deals with the stripping of regolith on a steep slope by surface wash and shallow landslides and a deep-seated landslide at a lower slope that took place on 17 February 2003 at the village of Mazilik, east of Canakkale, Turkey. Soil loss and shallow slides dominate on the deforested steep slopes in the study area and occur preferentially along slope-parallel sub-horizontal joint planes with clay coatings, particularly oxyhydroxides that are rich in Fe but poor in Mn as a result of weathering under well-drained conditions. Gully erosion also occurs where the regolith cover is relatively thick (up to similar to 4 m). The area of the deep-seated landslide, however, is dominated by silty clay (46%). A geoelectrical resistivity survey revealed a clay-rich zone at depths of similar to 3-10 m, corresponding to the slip surface of the slide, which was associated with excessive water content after the snowy day of 14 February 2003 with a daily precipitation of similar to 16.4 mm. Based on Thornthwaite's water budget analysis, the study area has a slide-prone condition with excess soil-moisture content, heavy rainfall events, snow accumulation and snow melting in winter months, and low soil permeability also favouring slope instability. (C) 2013 Elsevier B.V. All rights reserved.Öğe Simulation of temperature and precipitation climatology for the Central Asia CORDEX domain using RegCM 4.0(Inter-Research, 2012) Ozturk, Tugba; Altinsoy, Hamza; Turkes, Murat; Kurnaz, M. LeventThe Coordinated Regional Climate Downscaling Experiment (CORDEX) is a framework designed to coordinate international efforts on regional climate simulations. CORDEX domains encompass the majority of land areas of the world. Region 8 of the CORDEX basically covers Central Asia, with the corners of the domain at 54.76 degrees N, 11.05 degrees E; 56.48 degrees N, 139.13 degrees E; 18.34 degrees N, 42.41 degrees E; and 19.39 degrees N, 108.44 degrees E and with a horizontal resolution of 50 km. In the present study, the results of an experiment with the ICTP regional climate RegCM 4.0 model that was run for seasonal mean air temperature and precipitation total series are presented. The experiment consists of one simulation from 1989 to 2010 using ERA-Interim reanalysis data as the boundary condition, another simulation for the period 1970-2000 using the global climate model ECHAM5 A1B scenario data for forcing, and finally a simulation for the period 2070-2100 using the ECHAM5 A1B scenario projection data for forcing. Between these 3 simulations we determined the temperature and precipitation climatology obtained from RegCM 4.0 downscaling for Region 8 of the CORDEX framework. In spite of the diverse topography of the region, the temperature and precipitation climatology obtained by RegCM 4.0 from hindcast data captures the general characteristics of the climate of Central Asia. In winter, the warm temperature bias of the forcing data is slightly decreased by regional downscaling. The influences of the Indian monsoon system are well represented, as this region covers a large area towards the southern boundary of Region 8, even though the focus of this work was to capture the general characteristics of the whole region.Öğe Spatiotemporal variability of precipitation total series over Turkey(Wiley, 2009) Turkes, Murat; Koc, Telat; Saris, FaizeLong-term changes and trends in the series of monthly, seasonal and annual precipitation totals of 97 stations in Turkey were analysed by considering their spatial and temporal characteristics. Secular trends in precipitation series were examined with the Mann-Kendall rank correlation test for the general period 1930-2002, whereas spatial variabilities of, and relationships between, the precipitation series at 86 of these stations were investigated by the principal component analysis (PCA) for the period 1953-2002 when the length of data is at its best for the stations subjected to the PCA. Major findings of the paper can be summarized as follows: (1) First principal component (PC1) generally describes climatology of the precipitation totals in Turkey that is closely governed by the large-scale and/or synoptic scale atmospheric features (i.e. surface and upper air pressure and wind systems). (2) In winter, it is very likely that the greater PC1 loadings over the western and south-western parts of Turkey characterized mainly with the Mediterranean rainfall regimes indicate influence of the large-scale atmospheric circulation and associated weather patterns. However, smaller PC1 loadings over the north-eastern and eastern parts of Turkey are very likely related to the influence of the northerly mid-latitude cyclones, and the northerly and easterly circulations linked with the Eastern Europe and the Siberian originated high pressures on spatial variations of winter precipitation. (3) As for the long-term temporal variability, it was detected that there is an apparent decreasing trend in the winter precipitation totals of Turkey, whereas a general increasing trend is dominant in the precipitation totals of spring, summer and autumn seasons. (4) Observed decreasing trends are the strongest over the Mediterranean and the Mediterranean Transition rainfall regime regions. (5) Strong decreasing trends are also mostly found in winter months of the year, while apparent increasing trends show up at some stations in the months of April, August and October. Copyright (c) 2008 Royal Meteorological Society
