Yazar "Keskin, Asli Ulke" seçeneğine göre listele

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    Clustering of the Black Sea Region meteorological stations of Türkiye with fuzzy c-means, k-means, and silhouette index analysis methods by precipitation, temperature and wind speed
    (Hungarian Meteorological Service, 2025) Keskin, Asli Ulke; Kir, Gurkan; Zeybekoglu, Utku
    Recent years have seen a marked increase in the number of disasters caused by the effects of global climate change. In response, a range of studies have been conducted in T & uuml;rkiye and worldwide with the aim of reducing the impact of climate change.The classification of regions affected by climate change into similar classes in terms of climate parameters is crucial for the application of consistent methods in studies conducted in these regions. Consequently, the formulation of effective strategies to mitigate the repercussions of climate change in these regions is contingent upon the accurate determination of the aforementioned strategy.The observation records evaluated within the scope of the study were obtained from 31 stations of the Turkish State Meteorological Service in the Black Sea Region, encompassing the period between 1982 and 2020, encompassing precipitation, temperature, and wind speed records.. The maximum number of clusters was determined as 5, the cluster analysis study was carried out by using fuzzy c-means and k-means methods for 2, 3, 4, and 5 cluster numbers according to these three data together form a matrix. The determination of the optimum cluster numbers was carried out by silhouette index analysis. For the data matrix where precipitation, temperature, and wind speed were evaluated together, the most appropriate classification was obtained by the k-means method by choosing the number of clusters as 4.
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    Defining rainfall intensity clusters in Turkey by using the fuzzy c-means algorithm
    (Univ Zagreb , Andrija Mohorovicic Geophys Inst, 2020) Zeybekoglu, Utku; Keskin, Asli Ulke
    Turkey has seven traditionally accepted climatic zones that are defined primarily by maritime and topographic influences. Across these zones, the annual amount of rainfall, including its intensity and its seasonal distribution, vary considerably. These variations, which impact on both urban and rural communities, including the occurrence of water shortages and flash flooding events. are increasing in both frequency and magnitude due to global warming and climate change. Several types of climate occur in Turkey where climate zones have been defined with various methodologies. To better understand rainfall intensity patterns across Turkey, this study used the Fuzzy C-Means (FCM) algorithm to define their spatial distribution. In the first stage, the annual maximum rainfall intensity records for periods ranging from 30 to 78 years were obtained from 95 stations operated by the Turkish State Meteorological Service, and the longitude, latitude and altitude data for the stations were compiled for cluster analysis. Secondly, all rainfall intensities and geographical values were normalized, and in the third stage. the FCM algorithm was applied. The comparison of annual maximum rainfall intensities revealed five clusters. Four clusters were identified as discrete zones and one was identified as a transitional zone. Weather stations located in different geographical regions sometimes fell into the same clusters. In other words, rainfall events of similar intensity can occur in different climatic zones. This study, which brought a different perspective to clustering studies, showed that rainfall intensity values can be successfully analyzed at a national scale with the FCM technique.
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    Detrended fluctuation analyses of rainfall intensities: a case study
    (Inderscience Enterprises Ltd, 2020) Zeybekoglu, Utku; Keskin, Asli Ulke
    The main source of the irregularity in the rainfall regimes is global climate change. These irregularities in the precipitation regime cause sudden and heavy rains, which increases the risk of flooding especially in cities. Therefore, the investigation of the change in precipitation intensities over time has great implications in terms of hydrology, water resources and urbanisation. In this study, rainfall intensity of Artvin meteorological station which is located in the Black Sea Region of Turkey is investigated. This station differs from the other stations in the Black Sea Region with extreme rainfall characteristics. Data of 14 standard duration rainfall intensity series with durations of 5 min to 24 h were used. First of all, two methods were applied for homogeneity control and then trend analysis was performed. Assuming that the factor destabilising the homogeneity is the trend, a detrended fluctuation analysis (DFA) was performed. After the implementation of DFA, homogeneity and trend analysis were reapplied to the data. In conclusion, it was determined that the main reason for the deterioration of rainfall intensity was the trend.
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    Effects of Southern Oscillation and North Sea-Caspian Pattern on the rainfall intensity series in the Black Sea Region of Türkiye
    (Hungarian Meteorological Service, 2026) Keskin, Asli Ulke; Kazembeigi, Reza; Zeybekoglu, Utku
    This study investigates the influence of the Southern Oscillation and North Sea-Caspian Pattern on maximum rainfall intensities in the Black Sea Region of T & uuml;rkiye. Annual maximum rainfall intensity series from 16 meteorological stations were analyzed, and correlation coefficients were calculated and evaluated at . = 0.01, 0.05, and 0.10 significance levels. Results indicate that the Southern Oscillation predominantly affects short-and medium-duration rainfall in Sinop, whereas the North Sea-Caspian Pattern shows significant correlations with medium-and long-duration rainfall in Bart & Otilde;n, Bayburt, and G & uuml;m & uuml;& uacute;hane. These findings highlight the spatially varying influence of atmospheric oscillations on rainfall extremes in the region.
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    Evaluation of the relationships between atmospheric indices and rainfall intensities: Black Sea region Türkiye
    (Elsevier, 2024) Keskin, Asli Ulke; Kazembeigi, Reza; Zeybekoglu, Utku
    Recent studies show that global atmospheric oscillations are effective on climate parameters. In this study, the relationship between the North Atlantic Oscillation and the Arctic Oscillation with the annual maximum rainfall intensity series throughout the Black Sea region of T & uuml;rkiye was investigated. In this context, the correlation coefficients between atmospheric oscillations and rainfall intensities were calculated. The correlations obtained were evaluated at the significance levels of alpha = 0.01, alpha = 0.05 and alpha = 0.10 according to Student t test. As a result of these evaluations; It was determined that the Arctic Oscillation was effective on rainfall intensities in & Ccedil;orum, Artvin, Rize and Bart & imath;n. In particular, significant correlations were found in all standard times in Artvin. Significant correlations were found between the North Atlantic Oscillation and the standard rainfall intensity series in & Ccedil;orum, Sinop, Artvin, Rize and Bayburt.
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    Future changes in drought characteristics in the Central Black Sea region of Türkiye using HadGEM2-ES climate models and the SPI
    (Springer, 2025) Kurtoglu, Selcuk Erdem; Keskin, Asli Ulke; Zeybekoglu, Utku
    This study investigates future changes in meteorological drought characteristics in the Central Black Sea Region of T & uuml;rkiye (Tokat, & Ccedil;orum, Amasya, Ordu, and Samsun) for the period 2023-2080. Using precipitation projections from the HadGEM2-ES climate model under RCP4.5 and RCP8.5 scenarios, the Standardized Precipitation Index (SPI) was applied at 1-, 3-, 6-, and 12-month timescales. The analysis reveals a reduction in the frequency of near-normal wet conditions, alongside a noticeable increase in the frequency and severity of dry periods, particularly in the inland provinces. Although some coastal areas are projected to receive more precipitation, drought conditions are still expected to intensify, reflecting complex regional responses to climate change. The results of this study are intended to support long-term water resource management, agricultural planning, and climate adaptation efforts in the region.
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    Investigation of Applicability of Artificial Bee Colony Algorithm on Rainfall Intensity Duration Frequency Equations
    (Polish Soc Ecological Engineering, 2020) Zeybekoglu, Utku; Keskin, Asli Ulke
    The main objective of this study was to investigate the applicability and efficiency of an artificial bee colony optimization algorithm to determine two statistical-based rainfall intensity duration frequency equations' weighting parameters. For this aim, the annual maximum rainfall records were obtained from seven meteorological stations of seven geographic regions in Turkey. It was observed that the Artificial Bee Colony algorithm, which is an alternative technique for solving the rainfall intensity duration frequency equations, gives very good results in selected seven meteorological stations.
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    K-means clustering of precipitation in the Black Sea Region, Türkiye
    (Hungarian Meteorological Service, 2025) Keskin, Asli Ulke; Kir, Gurkan; Zeybekoglu, Utku
    In recent years, there has been a significant uptick in the frequency of disasters stemming from the impacts of global climate change. In response, both nationally and internationally, various studies are being conducted to mitigate these effects. Classifying regions affected by climate change into similar classes based on climate parameters is crucial for applying consistent methodologies in studies conducted within these regions. This approach will help determine the most appropriate strategies for mitigating the effects of climate change in these regions. The study utilized observational records of annual precipitation from 31 stations in the Black Sea Region, sourced from the Turkish State Meteorological Service, covering the data spans the period between 1982 and 2020. Cluster analysis was conducted using the k-means algorithm. The optimal cluster among those formed was determined through the silhouette index analysis. The study suggests that the optimal number of clusters is 2.
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    The Temporal Trends of the Turkish Black Sea Rainfall Intensities Series and Relationships with Global Atmospheric Indices: 1966-2015
    (Springer Basel Ag, 2025) Keskin, Asli Ulke; Kazembeigi, Reza; Zeybekoglu, Utku
    The extent of research indicates that global atmospheric oscillations exert a significant influence on climate parameters. This study aims to investigate the relationship between major atmospheric oscillations and annual maximum rainfall intensities across the Black Sea region of T & uuml;rkiye between 1966 and 2015. To this end, correlation coefficients were computed-assessed for statistical significance at the alpha = 0.05 level using the Student's t-test. Additionally, temporal trends in rainfall intensities were examined using the innovative trend analysis (ITA) method. The results suggest that the Arctic Oscillation and the North Atlantic Oscillation have a more pronounced effect in the eastern parts of the region. However, the ITA findings revealed no statistically significant trends in rainfall intensities across the study period.