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The wind has considerable effects on the ecosystem and evaporation as an essential parameter of the hydrological cycle. Therefore, determining historical changes in the wind will help to specify these effect levels. Although there are studies on the determination of wind speed trends by several researchers in Turkey, it is necessary to investigate the changes in the trend structure with recent data. For this purpose, the trends of monthly surface wind speed data from 1970 to 2021 belonging to 199 meteorology observation stations in Turkey are determined in the present study. The nonparametric Mann–Kendall test and Sen's slope method are used in the trend analysis accounting for serial correlation effects. The trend analysis results of wind speed data are evaluated temporally and spatially for seven geographical regions within Turkey. As a result of this study, a prominent part of stations in Turkey shows a decrease or significant decrease trend. In addition, as a result of comparisons made with previous studies, it is determined that the trend structure of the wind speed in the country has changed. In the annual and monthly wind speeds, it is observed that the number of stations has a "significant trend" decreased considerably. [ABSTRACT FROM AUTHOR]

Understanding how natural ecosystems are and will be responding to climate change is one of the primary goals of ecological research. Plant phenology is accepted as one of the most sensitive bioindicators of climate change due to its strong interactions with climate dynamics, and a vast number of studies from all around the world present evidence considering phenological shifts as a response to climatic changes. Land surface phenology (LSP) is also a valuable tool in the absence of observational phenology data for monitoring the aforementioned shift responses. Our aim was to investigate the phenological shifts of Fagus orientalis forests in Turkey by means of daily MODIS surface reflectance data (MOD09GA) for the period between 2002 and 2020. The normalized difference vegetation index (NDVI) was calculated for the entire Turkey extent. This extent was then masked for F. orientalis. These "Fagus pixels" were then filtered by a minimum of 80% spatial and an annual 20% temporal coverage. A combination of two methods was applied to the time series for smoothing and reconstruction and the start of season (SOS), end of season, and length of season parameters were extracted. Trends in these parameters over the 19-year period were analyzed. The results were in concert with the commonly reported earlier SOS pattern, by a Sen's slope of −0.8 days year−1. Lastly, the relationships between SOS and mean, maximum and minimum temperature, growing degree days (GDD), and chilling hours (CH) were investigated. Results showed that the most significant correlations were found between the mean SOS trend and accumulated CH and accumulated GDD with a base temperature of 2 °C, both for the February–March interval. The immediate need for a phenological observation network in Turkey and its region is discussed. [ABSTRACT FROM AUTHOR]

Despite the recent popularity of studying the effects of climate change on critical regions worldwide, there is a paucity of data documenting the results from trend analysis for these regions based on hydro‐climatic variables such as precipitation and temperature. The purpose of this study was to undertake a spatio‐temporal precipitation and temperature trend analysis for the Seyhan and Ceyhan River Basins located in the south of Turkey. The data for the seasonal and annual temperature variations (minimum, maximum and mean) and the total precipitation outputs obtained from the 14 stations in these basins are considered. The non‐parametric Mann–Kendall and the Mann–Kendall rank correlation tests are employed to determine the trend and its year of initiation. The linear slopes of the trends are calculated by using Sen's slope estimation technique and the spatial distributions for the slope of trends are presented. The results show that statistically significant upward trends exist for these basins based on the annual maximum temperature values, and the years of initiation of the trends are determined as mid‐1990 and mid‐2000. [ABSTRACT FROM AUTHOR]

ABSTRACT This study examines the spatial and temporal dynamics of wind speeds over Turkey by analysing data from 206 weather stations for a 32-year period (1975-2006). Trends in annual, seasonal, and monthly average wind speeds were determined using the Mann-Kendall trend test with the trend-free pre-whitening procedure. The strengths of trends were estimated by calculating the Sen's slope. The possible causes of wind speed changes were discussed. The analysis showed that the majority of the stations (73%) in Turkey had average wind speeds between 1.6 and 3.3 m s−1 during the 32-year period. From 1975 to 2006, 72% of stations had downward trends in annual average wind speeds. Downward trends were statistically significant at the 0.05 level for 62%. Significant upward trends were detected in only 16% of 206 stations. The rate of change in annual average wind speed data was on average −0.014 m s−1 year−1. The trends detected in monthly average wind speed data were mostly downward with an average strength between −0.007 and −0.017 m s−1 year−1. The directions and strengths of wind speed trends identified for the 1975-2006 period over Turkey are similar to the trends detected in wind speeds in many other regions over the earth. The changes in wind speeds in Turkey are most strongly related with the changes in general circulation patterns and air temperatures. The effects associated with changes in surface roughness and data quality are minor compared to other two factors. [ABSTRACT FROM AUTHOR]

Trend analysis benefits collecting and analyzing reliable data in climate change studies. In this context, long-term temperature and precipitation data analysis, two variables sensitive to climate change, is essential. This study aims to holistically and partially determine the annual trends of precipitation and temperature time series for 1970–2019 at nine selected stations in the Susurluk Basin, Turkey. The innovative trend significance test (ITST), innovative crossing trend analysis (ICTA) method, and Mann-Kendall (MK) test were used to determine holistic trends. Also, partial trends were determined using successive average methodology (SAM). For the precipitation variable, while an increasing trend was determined for the ITST, there was mostly no trend for the other methods. While a strong increasing trend was detected for the temperature according to the ITST and MK methods, no trend was observed in any station according to the ICTA method. According to the SAM results, the maximum trend durations for the peak and trough change points were 4.9 (10.3) and 5.3 (8.4) years, respectively, for precipitation (temperature). The strong temperature trends in the basin will likely continue, requiring precautions against extreme events such as drought. [ABSTRACT FROM AUTHOR]

This paper investigated the trends and variability in warmest daily maximum (TXx) and warmest daily minimum (TNx) air temperatures, and heatwave characteristics in Turkey in May during 1950–2020. It also analysed the climatological and synoptic meteorological evolutions of heatwave (HW) observed in May 2020. Trend analysis revealed significant increasing trends in TXx and TNx series and heatwave characteristics in May since 1950. Since the mid‐1980s, a continuously increasing trend in TXx and TNx series, and the number, frequency, and magnitude of the heatwaves were observed that accelerated with the mid‐1990s. The most severe heatwave in Turkey since 1950 in May was observed in 2020. The record‐breaking daily maximum (daily minimum) air temperatures were noted at 32 (23) of 96 stations in May 2020, mainly over Turkey's western and southern parts. Record‐high maximum (minimum) air temperature was 43.2°C (31.1°C) reached for the first time in May since 1950. The generalized extreme value model applied to the May TXx and TNx series revealed that the daily air temperatures in May 2020 exceeded 100 years' return periods at many stations of Turkey. This heatwave was linked to a regionalized strong anticyclonic blocking anomaly circulation and other associated atmospheric anomalies in May 2020. This also resulted in the centring of an unprecedented subsiding, calm, and stable warm air mass over Turkey. Adiabatic warming and drying developed very likely under subsidence control because of relatively weak circulation conditions. Such circumstances resulted in extremely hotter conditions in May 2020 compared to the long‐term averages. [ABSTRACT FROM AUTHOR]

Significant changes in the onset, length and thermal characteristics of seasons have been reported all over the globe in recent decades; however, the spatiotemporal changes of seasonal characteristics in Turkey have received little attention in relation to seasons delineation. In this study, the changes in the characteristics of Turkish seasons have been examined from 1965 to 2020 by considering the daily average temperature data obtained from 65 meteorological stations. A nonstatic definition of season onset was used to delineate the seasons. The study also presents the response of seasons timing and thermal characteristics affected by climate change. All over Turkey, the trend rate for beginning of summer was determined to be 2.1 days·decade−1 from 1965 to 2020, while the beginning of winter has shifted forward at many stations in southeastern Anatolia. All the seasons have experienced increases in average temperatures. The maximum increase was in summer seasons and occurred at up to a rate of 0.7°C·decade−1. There has been almost no change in winter temperatures over the Mediterranean region. Eastern Marmara with the western and middle Black Sea regions experienced an extension of spring as well as a shortening of the autumn season. It was noted that the change in the beginning of summer occurred all over the country. However, the extension of spring and shortening of the autumn season was mainly limited to the western Black Sea regions. The seasons, defined by considering climate change and variability, showed significant trends for length, average temperature and their onset. To the best of the author's knowledge, the delineation of seasons using a dynamic approach is the first attempt of its kind in this study area. [ABSTRACT FROM AUTHOR]

Drought is caused by the imbalances in the factors that make up the hydrological cycle, especially the rainfall. Droughts triggered by climate change can occur anywhere in the world. This study aims to conduct a detailed seasonal drought analysis through the monthly precipitation statistics of 126 observational points in Turkey during 1925–2016. The drought analysis was performed for four different periods: 1925–1949, 1950–1974, 1975–1999, and 2000–2016. First, the standardized precipitation index values were calculated with the Pearson Type III distribution. The 3-month period, used in seasonal drought analysis, was preferred. Information about the course of drought was obtained with the Mann–Kendall trend analysis. The severity, duration, and frequency of drought were found with the Theory of Runs model. The joint return period of drought severity and drought duration were obtained with the copula approach. The mapping was done with the inverse distance weighted method. The findings indicate that the lowest SPI value (− 2.12) was observed in spring 1972 and the highest SPI value (2.14) was observed in winter 1941. Very dry conditions were recorded with a frequency of 16% in the spring season of the 1925–1949 period; the most normal arid conditions were documented in the autumn season of 1950–1974 with a frequency of 52%. Extreme drought conditions were reported in the spring season in 1992. While there was an insignificant increase in drought in spring, summer, and winter, a significant increase was observed in autumn especially interior parts of Turkey. Theory of Runs results indicate that the highest intensity, with a value over 2, was observed in the southeast of Turkey during the winter and spring seasons during the 1925–2016 period. The Frank copula function was found to be the most suitable function in calculations of the drought severity and duration calculation for Turkey. The return periods of weak, moderate, and severe droughts were between 127.53 and 78.96, 68.85 and 59.60, 60.28 and 57.65 months, respectively. It was determined that the drought severity increased in the inner regions during the 20- and 100-year drought return periods with the values varying between 5 and 16, 7, and 32, respectively. [ABSTRACT FROM AUTHOR]

This study characterises the spatial and temporal behaviours of maximum precipitation over the Black Sea Region in northern Turkey. Maximum precipitation data of 14 standard durations changing from 5 min to 24 h were used from 21 meteorological stations in the region with record lengths ranging from 25 to 71 years. In line with the objective of the study, tests for the detection of outliers, homogeneity, and trend were applied in order to reveal the structural characteristics of the data set. Tests detected no outlier, and the homogeneity analysis found only three stations fully homogeneous, all others being inhomogeneous. Change points identified in the data set by the homogeneity tests were linked to the local characteristics of meteorological stations. Trend analysis revealed that slightly more than half of the meteorological stations are exposed to a positive trend in the maximum precipitation of one standard duration at a minimum. The main conclusion is that maximum precipitation is subject to change over the Black Sea Region in Turkey. [ABSTRACT FROM AUTHOR]

The aim of this study is to conduct a drought analysis at Kars station in the northeast of Turkey using six different meteorological parameters by utilizing The Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) method based on the entropy weight method. As of the input parameters of the study, the mean monthly rainfall, mean monthly maximum and minimum temperature, mean monthly relative humidity, mean monthly wind speed, mean monthly sunshine duration, obtained by the Kars meteorology station for 1990 and 2018 period are used. In the second section of the study, Mann–Kendall trend analysis was applied to TOPSIS results. The findings of this study indicated that the drought tends to increase in January, May and October. In the final section of the study, multivariate regression analysis, which accepts six different parameters as independent variables and TOPSIS drought index results as dependent variables, was performed. According to the findings of this study, there were no cases of extreme wet, severe wet, medium wet, severe drought and extreme drought at the Kars station. The driest months are May and June. The wettest months are March and November. [ABSTRACT FROM AUTHOR]

Warm-season (from May to September) pan evaporation series recorded at nine sites in semi-arid Büyük Menderes Basin in Western Turkey were analyzed for evidence of long-term changes using non-parametric Mann-Kendall test. Only two sites showed significant linear trends, one in decreasing direction and the other in increasing direction. Area-averaged normalized anomalies of pan evaporation stayed unchanged over the period 1975-2006. Based on correlation and multiple regression analysis with visual inspection of the time series plots, sunshine duration which is used as a proxy for global radiation was found to be the major factor explaining the change and variability of pan evaporation in warm-season in semi-arid Büyük Menderes Basin. Stepwise multiple regression analysis showed no significant effect of rainfall on pan evaporation, which means that the effect of complementary relationship is rather weak and even non-existent. [ABSTRACT FROM AUTHOR]

Climate change is an event that has significant effects as direct or indirect on ecosystem and living things. In order to be prepared for the effect of climate change, it is necessary to anticipate these changes and take measures for this change. Therefore, many studies have been carried out on changes in climate parameters in recent years. The most common method used in these studies is trend methods. Innovative Polygon Trend Analysis (IPTA) and Trend Polygon Star Concept are trend analysis methods. IPTA Method divides data series into two as first and second data set and analyzes these two data sets by comparing them with each other. Trend Polygon Star Concept analyzes distance between two months in data set in graph, which is result of IPTA, and shows analysis result by dividing it into four regions. Therefore, in this study, monthly average temperature data are analyzed by using this two-polygon method. This data set is for 22 years (1996–2017). Polygon graphics were created as a result of study. Besides, trend slopes and lengths of temperature data with IPTA Method were calculated. The values of graphs created with Trend Polygon Star Concept Method on x- and y-axis were given in a table. When the results of both analysis methods were examined for a station, the following results were observed. For example, a regular polygon was not seen in arithmetic mean and standard deviation graphs of IPTA Method of Bandirma Station. Besides, when general evaluation of arithmetic mean analysis results was examined an increasing trend in most months. When arithmetic average graph created by Trend Polygon Star Concept Method of Bandirma Station was examined, transition between two months was seen first and third region. When standard deviation graph was examined, transitions between two months were seen in all four regions. [ABSTRACT FROM AUTHOR]

Irrigation water quality has important implications on salinity, ion toxicity, production cost, and crop failures. There is a need for a comprehensive analysis of spatial and temporal dynamics in parameters at a watershed scale. This information is critical for irrigation management in agricultural production. The Lake Uluabat watershed is a significant agricultural area of Turkey, which is studied using monitored water data. Multivariate assessment is performed using cluster analysis (CA), discriminant analysis (DA), principal component analysis (PCA), and factor analysis (FA) to evaluate temporal and spatial variations in water quality in the watershed. The data is processed by clustering, reducing data dimensionality, delineating indicator parameters, assessing source identification, and evaluating temporal changes and spatial patterns. The results show that the most representative discriminant parameters had more than 90.98% validity in both temporal and spatial analyses. Runoff rate (Q) and water temperature (WT) were identified in the temporal study, while spatial analysis showed bicarbonate (HCO3−), sulfate (SO42−), and boron (B3+) as indicators. Salinity, sodicity, boron hazard, and alkalinity affect both spatial and temporal water quality patterns in the watershed. It is observed that continued use of poor-quality irrigation water can adversely affect agriculture and soil health in a watershed. Spatio-temporal relationships in parameters will be useful in sustainable irrigation management and farm planning for improving crop productivity and soil health. [ABSTRACT FROM AUTHOR]

The satellite observations of NO2 acquire the total tropospheric column over an area while the current ground observations lack spatial and temporal coverage. In this study the Dutch Ozone Monitoring Instrument (OMI) NO2 (DOMINO) data product v2.0 for 2004 - 2019 period was used to analyze the spatial and temporal variations of NO2 in Turkey. Considering the seasonality characteristics of NO2, we have used pixel based Seasonal Kendall (S-K) test to investigate the trend of the change. The highest values of NO2 has been found at the metropolitan areas and perimeter of the high capacity power plants in the observed period. The monthly average concentrations of NO2 are higher in winter months due to the higher demand of heating and power usage. The S-K trend test results indicate a statistically negative trend at the largest cities such as Istanbul, Ankara and Izmir. However statistically significant positive trend has been found in some areas and Syrian border provinces in particular. Our results show that there is an abrupt change by 2011 in the tropospheric NO2 concentrations, same period when the first Syrian refugees have arrived after the political disorder. The dramatic change at the emission landscape of the NO2 in the region can be explained by changes in population concentration due to political circumstances. [ABSTRACT FROM AUTHOR]

In this study, annual and seasonal precipitation trend analysis was performed in the Euphrates-Tigris basin, Turkey, using innovative trend analysis (ITA) and discrete wavelet transformation. In this context, it was seen that there is a downward trend in winter, spring and annual precipitation, whereas precipitation has an increasing tendency in summer and autumn seasons, in the greater part of the basin. When annual and seasonal data were decomposed into wavelet components, the most significant trends were observed for high-periodic wavelet components, such as D3 (8-year), D4 (16-year) and D5 (32-year), where these components represent the periods of the precipitation data. Then, the relationship between North Atlantic Oscillation (NAO) and trend in precipitation was investigated. In this regard, it was found that there could be a significant relationship between the NAO and precipitation trends of the Euphrates-Tigris basin, especially in winter, based on the wavelet ITA. [ABSTRACT FROM AUTHOR]

The aim of the study was to evaluate the sediment prediction performance of Revised Universal Equation (RUSLE) and Musgrave Equation at the Ekinli pond catchment, North central part of Turkey. Ekinli pond was built in 1977 for irrigation purposes. The accumulation of sediment in the ponds negatively affects their functions. There are many dams located within the study area whose operations have been adversely affected by excessive reservoir sedimentation. Accurate estimation of sediment deposition is important in the design of a pond. The calculated amount of sediment volume deposited in the Ekinli reservoir was 21600.75 m³ and the average sediment yield was 514.3 m³ y-1 between 1977 and 2018. In the Ekinli basin, the availability of bathymetry measurements between 1981 and 2006, provided the appropriate conditions to validate the results of the predicted sediment yield since the deposited sediment volume could be quantified as 552.3 m³ y-1. The measured and estimated sediment amounts for the Ekinli reservoir have shown an excellent accordance. In the 42-year time period, 6.74% of the water storage capacity of the pond has been lost. From 1977 to 2000, the entire basin was grassland and 38% of the basin area has been afforested. The landuse change reduced a little the amount of sediment in the reservoir. The Mann–Kendal and Theil–Sen Slope estimator statistics indicated a decreasing trend of sediment amount. [ABSTRACT FROM AUTHOR]

This paper addressed the spatial and temporal variations of precipitation concentration across western Turkey, by analyzing daily and monthly precipitation time series recorded at 28 stations over the period 1966-2011. Four indices: daily precipitation concentration index (DPCI), monthly precipitation concentration index (MPCI), precipitation concentration degree (PCD) and precipitation concentration period (PCP) were used. The results showed higher values of DPCI in northwestern and southern parts and lower values in western-central, central, eastern and northeastern parts, and the southern part was the most critical part of the study area, with the highest values of DPCI, MPCI, PCD and annual total precipitation, but the lowest number of rainy days. MPCI and PCD values showed a seasonal precipitation regime over the whole study area and exhibited a pattern decreasing from southwest to northeast, which implies a more uniform distribution of monthly rainfall in a year toward the northeast. PCP values showed that annual precipitation mainly falls in December and January. Trend analysis demonstrated mostly non-significant decreasing trends for all indices, implying a very slight tendency toward a more regular precipitation distribution in a year and a slightly earlier occurrence of precipitation over western Turkey. [ABSTRACT FROM AUTHOR]