Observed Changes in Annual and Seasonal Temperatures in Nevşehir (Central Anatolia, Turkey) for Period 1960-2016

Eurasian Journal of agricultural research Observed Changes in Annual and Seasonal Temperatures in Nevşehir (Central Anatolia, Turkey) for Period 1960-2016 Türkan Bayer Altın1* 1 Niğde Ömer Halisdemir University, Faculty of Science and Letters, Department of Geography, 51240, Niğde, Turkey. *Corresponding Author: e-mail: Abstract This study investigated changes and trends in mean annual and seasonal temperatures together with temperature anomalies in the province of Nevşehir, Turkey for the period 1960-2016. Nevşehir is within the Central Anatolia Region which is potentially sensitive to climate change due to its semi-arid climate. Trends in temperature series were analysed using MannKendall and Gaussian statistical tests. Results show statistically significant increases in mean annual and summer temperatures at 0.05% level. A significant increasing trend in spring and autumn temperatures is weaker than summer temperatures. In other words, a slight warming trend in all these three seasons was detected. For winter temperatures, an increasing trend was also detected in this period. The trends, both annually and in summer, are evident from 1994, when the mean annual temperatures were above the long-term average. The warmest year was 2010 and the coldest year was 1992. Keywords: Climate change, trend, temperature, Mann-Kendall, Nevşehir INTRODUCTION Climate scientists have reported a warming tendency in the global average surface temperature. Their studies have shown that in the last 150 years there has been an increase of 0.8°C in global mean temperatures and 1°C in Europe (IPCC, 2012). The study area of Nevşehir province is located in the vicinity of Cappadocia within the Middle Kızılırmak SubRegion of the semi-arid Central Anatolia Region, which is sensitive to climate change. While the results of studies indicate that there is an overall upward trend here in extreme and average temperatures (Türkeş et al., 1996; Türkeş, 1999, Türkeş et al., 2009; Toros, 2012), there have also been positive trends in minimum temperatures and a statistically significant upward trend in summer temperatures, especially in Nevşehir (Kızılelma et al., 2015). According to (Türkeş, 2005), Nevşehir and its environs is the most continental part of Cappadocia with high inter-annual variability and low temperatures. Nevşehir has an arid and sub-humid climate, first mesothermal, (excess of water is too little during the year) and the summer concentration of temperature activity is equal to the third mesothermal (Türkeş, 2005). In another study (Türkeş and Akgündüz, 2011), the Cappadocia region is subject to desertification due to both natural factors (drought, climateprocess system, tuff separation, erosion, climate change) as well as human influence (land degradation, intensive tourism). In studies on the tourism of Nevşehir, it was noted that it is possible to stay outdoors all day owing to comfortable weather conditions in the summer (Türkoğlu and Çalışkan, 2011; Çalışkan and Matzarakis, 2012). Türkoğlu and Çalışkan (2011)’s study detected that for the PET (Physiologically Equivalent Temperature) values of all hours of the day, an increasing trend has been found in Nevşehir (urban meteorological station). In a study on the effects of temperature and rainfall changes on the soil and water 4 Eurasian Journal of agricultural research resources of Nevşehir, it was suggested that a serious additive trend was observed in the average, maximum and minimum long term temperature (Bağdatlı et al., 2015). Studies on Turkey in recent years show the occurrence of extreme temperature events in the summer and an increase in annual changes in the second half of the 20st century (Türkeş et al., 2011; Erlat and Türkeş, 2013; Öztürk et al., 2014). Türkeş (1998) pointed out that Turkey is influenced by the hot and arid climate prevailing in the Middle East and North Africa. Increases in temperature and anomalies there bring problems such as drought and floods in the Central Anatolia Region, especially in the case of natural vegetation cover, variety of agricultural products and water resources. The purpose of this study is to determine the trends of Nevşehir province in the last 57 years using monthly, annual and seasonal temperature data. GEOGRAPHIC SETTING and CLIMATE Nevşehir province is situated between the coordinates 38° 12'-39° 20' north (latitude) and 34° 11'-35° 06' east (longitude) (UTM, ED 50, Zone 36 N) and in the southern part of the Kızılırmak River valley. The province, which belongs to the Middle Kızılırmak Sub-Region, has different topographical features and elevations varying between 910-3900 metres. Moreover, Nevşehir is located within the area known as Cappadocia, which is a popular tourist destination and covers a large plateau formed by accumulation of the ash and lava from extinct volcanoes such as Mt. Erciyes (3916 m), Mt. Melendiz (2963 m) and Mt. Hasan (3268 m). It is surrounded by these mountains to the south and east (Figure 1). Thus, geographically, while Cappadocia is centred on the city and province of Nevşehir, it also encompasses parts of Kayseri, Niğde, Kırşehir and Aksaray provinces. 5 Eurasian Journal of agricultural research Figure 1. Location and DEM map of Nevşehir province. Figure 2. Variability in annual mean temperatures of Nevşehir province. MATERIALS and METHOD In this study, the changes and trends in the mean annual, seasonal temperature and anomaly series of Nevşehir using 57 years of data were examined. Gaussian Filter was used to examine the long-term fluctuations visually in the mean series. In this method of filtering, the weighting of successive terms of series varies symmetrically both backwards and forwards from a central weight (WMO, 1966; Türkeş et al., 1996). In addition, Mann-Kendall rank correlation coefficient was used to determine nonlinear trends in the time series. The u(t) curve obtained from this analysis shows the trend in the observation series. 6 Eurasian Journal of agricultural research The u(t) and u'(t) curves overlapping several times show that there is no significant trend in the series. Intersection of these curves shows the point where the trend begins (Sneyers, 1990). RESULTS AND DISCUSSION When the changes in annual temperature anomalies in Nevşehir from 1960 to 2016 are examined, periods occurred where decreasing and increasing trends can be distinguished, as well as the interannual variability (Figure 3). Figure 3. Changes and trends in mean annual temperatures of Nevşehir. (a) Red columns and blue curve show annual anomalies and 9-point Gaussian Filter, respectively. (b) Trend in annual temperature series according to u(t) and u'(t) obtained from Mann-Kendall test. The Gaussian graph (Figure 3a) shows that a relatively warm period is observed between 1960 and 1966. This period was followed by a significantly cold period between 1971 and 1993. Following this period, a significant warming trend is observed despite the variab (...truncated)