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Comparative analysis of SPI, SPEI, and RDI ındices for assessing spatio-temporal variation of drought in Turkiye ( Jul, 10.1007/s12145-024-01401-8, 2024)
(Springer Heidelberg, 2024) Yaman Öz, Fatma; Özelkan, Emre; Tatlı, Hasan
Defining Holdridge's life zones over Turkey
(Wiley, 2016) Tatlı, Hasan; Dalfes, H. Nüzhet
This study is proposing a classification for the Holdridge's life zones associated with the surface climatic variables over Turkey. Holdridge's scheme is aiming to group meteorological and climatic quantities at the regional scale according to some pre-defined rules. On the other hand, without rules or pre-defined restrictions, the process of combination of similar stations in groups is recognized as clustering. A spectral clustering method was suggested for identifying the characteristics of the local climate over the country. To increase the proxy value of the estimated life zones, the missing values in the data sets of temperature and precipitation series were filled by fitting appropriate theoretical variogram. A programme coded in Fortran 95 was developed for determining the life zones. The probabilistic features of the life zones were estimated by using empirical cumulative frequencies. In addition, a new spectral clustering method based on Sampson correlation ratio was developed for clustering high-dimensional data. From these results, four major categorical life zones were obtained, namely montane, lower montane, cool temperate and warm temperate. Additionally, 14 types of the Holdridge's vegetation classes were estimated, the frequent zones are cool temperate steppe and warm temperate dry forest; some moist forests are seen particularly in the eastern Black Sea region, the rainiest region of the country. The suggested spectral clustering method is capable of capturing the principal life zones. The tendency of life zones shifting towards the climate conditions of lower latitudes indicates that the long-term meteorological normals changed; this is exactly the point of climate change. A better understanding of life zones of Holdridge hopefully can contribute to sustainability plans of the policy makers.
Empirical Orthogonal Function analysis of the palmer drought indices
(Elsevier, 2011) Tatlı, Hasan; Türkeş, Murat
The aim of the paper is to employ Empirical Orthogonal Function (EOF) analysis to drought indices including Palmer Drought Severity Index (PDSI), Palmer Hydrological Drought Index (PHDI), Palmer Moisture Anomaly (Z) Index (Z-Index), Weighted Palmer Drought Severity Index (WPDSI), and Water Deficit (P-PET) Index and to compare their resultant spatial patterns across Turkey. In this respect, the PDSI, PHDI, Z, WPDSI, Aridity Index (AI) and P-PET Index values are calculated based on observed monthly temperature and precipitation values of the 96 Turkish meteorological stations for the 1929-2009 period, and gridded available water holding capacities (AWHC) in 1-m soil depth are extracted from the soil data sets of the Oak Ridge National Laboratory Distributed Active Archive Centre (ORNL DAAC). By considering the strong match among the PDSI, PHDI, and WPDSI based on the results of the patterns of the first EOFs (EOF1) with the highest eigenvalue, we suggest that using and applying one of these drought indices could be adequate for a drought analysis in Turkey. On the other hand, it is evident that the significant results from the EOF2, EOF3 and EOF4 loadings of the PHDI and WPDSI indices have a similar pattern across Turkey. Therefore, with respect to the geographical autocorrelation and magnitudes of the loading values, it is explained that the PDSI and WPDSI in particular could have originated from the same physical process, and one may have a preference for the effective usage of a combination of PDSI, PHDI and Z-Index. Consequently, in a multi-purpose medium- and long-term drought management plan for Turkey or in any country having similar climatic and physical geographical conditions, using one of the three drought indices along with the Z-Index could be acceptable for successful applications. (C) 2011 Elsevier B.V. All rights reserved.
Assessment of multidimensional drought vulnerability using exposure, sensitivity, and adaptive capacity components
(Springer, 2023) Serkendiz, Hıdır; Tatlı, Hasan
This study provides a method for analyzing the drought-vulnerability index (DVI) from a multidimensional perspective that includes biophysical and social aspects, considering the Intergovernmental Panel on Climate Change's (IPCC) assessment. The proposed method generates the exposure index (EI), sensitivity index (SI), and adaptive capacity index (ACI) components of the proposed DVI using nine sub-indicators and 29 proxy variables. By using it throughout all of Turkey's provinces, the performance of the developed index was evaluated. In this study, the decision matrices were built utilizing expert knowledge, and the weights of the indicators and variables were obtained by using the Analytical Hierarchy Process (AHP) technique. Moreover, the values of these four indices were classified as very high, high, moderate, low, and very low, and their geographical distribution across the country was drawn, as well as relevant patterns retrieved. The study's major results show that 17 of the 81 provinces are classified as very high, 16 as high, 15 as moderate, 17 as low, and the remaining 16 as very low drought vulnerable. Another significant result is that the majority of people in the country's south, center, and southeast rely on agriculture and are thus more vulnerable to drought due to socioeconomic underdevelopment in those regions.
Multidimensional assessment of agricultural drought vulnerability based on socioeconomic and biophysical indicators
(Elsevier, 2023) Serkendiz, Hıdır; Tatlı, Hasan; Özcan, Hasan; Çetin, Mahmut; Sungur, Ali
Agricultural drought threatens Turkiye's food security and economy, revealing a lack of multidimensional provincial vulnerability studies. Therefore, the primary objective of this study is to evaluate Turkiye's vulnerability to drought utilizing a multidimensional strategy incorporating biophysical and socio-economic indicators. In this context, an initial step involved the development of a conceptual framework for drought vulnerability, drawing upon the Intergovernmental Panel on Climate Change recommended elements of exposure, sensitivity, and adaptive capacity. Subsequently, this conceptual framework was applied at the provincial level, encompassing parameters such as temperature, precipitation, soil characteristics, water resources, agricultural earnings, demographic traits, educational levels, innovation, insurance coverage, and road density. The Aridity Index was used as an indicator for drought exposure, representing the physical dimension of drought. Under the sensitivity component, a total of 14 variables were defined under the indicators of soil, water and land resources, economy, and population, while under the adaptive capacity component, a total of five variables were identified. The weights of these indicators and variables were determined based on expert opinions using the Analytic Hierarchy Process method. As a result, five different indices were obtained by combining the indicators: Exposure Index, Sensitivity Index, Adaptation Capacity Index, Potential Drought Impact Index, and Agricultural Drought Vulnerability Index. In addition, spatial distribution models of these indices were also generated. Research results showed that the climatic regions most exposed to drought are also the most vulnerable. The Central, Southeastern, and Eastern Anatolian regions constitute the regions where the most vulnerable provinces are concentrated spatially.
Use of the spectral clustering to determine coherent precipitation regions in Turkey for the period 1929-2007
(Wiley, 2011) Türkeş, Murat; Tatlı, Hasan
In this study, we suggest the spectral clustering (SC), a hybrid clustering technique based on singular value decomposition (SVD) and K-means for grouping features of precipitation totals of 96 stations in Turkey. Clustering process establishes an exhaustive set of occupied regimes into distinct climatic zones. Results of the SC satisfactorily represent the influences of the synoptic-scale weather systems including such as the mid-latitude and Mediterranean frontal cyclones, and the mid-latitude travelling and eastern Europe high pressures in winter, sub-tropical Azores high pressure and monsoon low in summer. Results of the SC also well display the influences of local-scale atmospheric disturbances, and direct influences of physical geographical features of Turkey (i.e. exposure, topography, orography, land-sea distribution, continentality and the high Anatolian peninsula) on the geographical variability and coherent distribution of the annual precipitation totals over Turkey. Finally, based on the results of the SC method employed to annual precipitation totals of 96 stations in Turkey for the period of 1929-2007, eight clusters of precipitation coherent zones are determined, namely Black Sea, Northwest Turkey, southern Aegean and western Mediterranean, Mediterranean, West Continental Central Anatolia, East Continental Central Anatolia, Continental eastern and south-eastern Anatolia. Copyright (C) 2010 Royal Meteorological Society
Use of the standardized precipitation index (SPI) and a modified SPI for shaping the drought probabilities over Turkey
(Wiley, 2009) Türkeş, Murat; Tatlı, Hasan
This paper suggests a new methodology for the Standardized Precipitation Index (SPI), for studying different aspects of drought events in Turkey, including intensity, frequency and identifying the spatial and temporal patterns. The classical SPI is locally defined; for instance, for monthly scale or running means, a drought event would begin when the precipitation amount is below its long-term average. However, the proposed method considers the local-time means of the precipitation series by fitting an upper and a lower envelope to precipitation data to obtain the SPI values, thus it explicitly assesses a dry (or wet) spell of weather. When we consider the climatological/meteorological features of precipitation and the physical geographical controls of the climate over Turkey, it is found that the proposed method is more capable of estimating the probability of dry or wet conditions for a station's monthly precipitation totals (or running means) than if the SPI values are obtained using the classical method. Comparisons of the probability values calculated for the long-term series and various time scales have revealed that the proposed method successfully estimates and/or well represents the various precipitation anomalies, particularly the wet and dry extremes. For instance, the probabilities of monthly values obtained by the proposed SPI method being above normal, below normal, near normal (i.e. normal) and extremely dry are more realistic and reasonable than those found by the classical SPI method. In conclusion, one can apply the proposed SPI methodology for determining and monitoring droughts of other semi-arid, dry sub-humid and semi-humid climate regions, where the precipitation series show high seasonality and year-to-year variability, such as in the Mediterranean macro-climate region. Copyright (C) 2009 Royal Meteorological Society
Land use suitability analysis of rural tourism activities: Yenice, Turkey
(Elsevier Sci Ltd, 2020) Kaptan Ayhan, Çiğdem; Cengiz Taşlı, Tülay; Özkök, Ferah; Tatlı, Hasan
In this study, a land use suitability analysis was conducted for rural tourism in the Yenice district, located in the north-west of Turkey. As part of the research process involved dividing the area in question into landscape units using GIS and RS techniques. A suitability rating for tourism activities in each landscape unit was obtained by following through the steps of the ELECTRE method, individually repeated for each landscape unit. It is considered that the 1st-, 2nd- and 3rd-degree suitable activities were most relevant in the rating of the nine different tourism activities. Therefore assessments were made on the basis of these first three ranks. As a result of the analysis, from the 1st-degree suitable activities identified, the first three were found to be mountaineering, trekking and wildlife observation. From the 2nd-degree suitable activities, the first three were flora observation, trekking and hiking, and from the 3rd-degree suitable activities, the first three trekking, orienteering and mountaineering.
Detecting persistence of meteorological drought via the Hurst exponent
(Wiley, 2015) Tatlı, Hasan
This study proposes the Hurst exponent (H) to detect persistence in the Palmer Drought Severity Index (PDSI) over Turkey. Since a fractal structure admits the behaviour of global determinism and local randomness, the H exponent values could be used to detect self-similar statistical structure of the time series. Additionally, the H value >0.5 and near 1 shows the intensity level of persistence. The term persistence may be assessed as a criterion to be used as a measure of predictability. Moreover, the predictability index, fractal dimension and autocorrelation function of the PDSI values can also be obtained from the H values. Nevertheless, it is not easy to find a spatial meaning of information content of the results obtained by the methods used in the present study. For that reason, the Mann-Kendall (MK) trend test was also used, and the results showed that significant negative trends are widespread throughout the country. As expected, the H values were close to 1 in places where statistically significant trends exist. The high values of the H exponent in all the regions can be explained by the droughts observed there that might be caused due to the possible associations with the large-scale atmospheric circulations. In this context, it is suggested that the droughts can be predictable by constructing the appropriate general climate circulation models.
Comparative analysis of SPI, SPEI, and RDI ındices for assessing spatio-temporal variation of drought in Türkiye
(Springer Heidelberg, 2024) Yaman Öz, Fatma; Özelkan, Emre; Tatlı, Hasan
This research presents a comprehensive drought analysis using climate data obtained from 219 homogeneously distributed meteorological stations in T & uuml;rkiye between 1991 and 2022. In this context, Standard Precipitation Index (SPI), Standardized Precipitation Evapotranspiration Index (SPEI) and Reconnaissance Drought Index (RDI) drought indices were used and comparative analysis was made. T & uuml;rkiye. The study demonstrates that below-normal precipitation over extended periods and increasing temperatures have contributed to the increased frequency of meteorological drought events. T & uuml;rkiye's topographic conditions, particularly its location in the Mediterranean basin, significantly influence drought occurrences. It is noted that over the past 20 years, T & uuml;rkiye has been trending towards drier conditions, with rising temperatures reinforcing this trend. The study observes that the moderate drought class range is the most frequently recurring in the SPI, SPEI, and RDI methods utilized. Regarding atmospheric conditions affecting the climate in T & uuml;rkiye, it is observed that increased drought severity stands out prominently in years when the North Atlantic Oscillation is positive. During these years, increased drought severity is evident in the SPI, SPEI, and RDI indices, particularly in winter and autumn, while a wide area experiences drought effects in the summer months. Long-term analyses emphasize that drought periods occur less frequently but have more prolonged impacts, attributed to variations in precipitation patterns from year to year and the influence of rising temperatures due to global climate change. The potential future increase in drought in the Mediterranean basin due to global climate change and T & uuml;rkiye's vulnerability to this situation could have adverse effects on water resources, food security, energy sources, and ecosystems.
Long-Time Memory in Drought via Detrended Fluctuation Analysis
(Springer, 2020) Tatlı, Hasan; Dalfes, H. Nüzhet
The persistence of drought events largely determines the severity of socioeconomic and ecological impacts, unfortunately the performance of current weather forecasting models (WFM) to simulate such events is subject to great uncertainties. This study is investigating time-domain characteristics of drought persistence over Turkey by applying the detrended fluctuation analysis (DFA) method to the Palmer drought severity index (PDSI). The existence of long-range power-law correlation in PDSI fluctuations is demonstrated for time scales ranging from monthly to decadal. Understanding of such statistical patterns in PDSI values can definitely be a step forward in drought predictability. From a climatological point of view, it is found that the areas with high level DFA scaling exponent (generalized Hurst) indicate the areas of higher sensitivity to droughts and associated risks. Furthermore, the characteristics of the persistence of the PDSI in climate zones have also been examined by applying the Holdridge Life Zones (HLZ) classification. HLZ classification over Turkey leads to two climate-zones: cool-temperate and warm-temperate. In addition, when topography is taken in account, montane (cool-temperate) and lower-montane (warm-temperate) climate zones can be treated as two different zones. It has been observed that the predictable index (PI) of the PDSI derived from the DFA Hurst exponent is relatively high in the cool-temperate and montane climate zones compared to others. In fact, very different PI values were also obtained in a few HLZ climate classes within the same climate zone and with same vegetation index (i.e. steppe, dry-forest, warm-forest etc.).
Synchronization between the North Sea-Caspian pattern (NCP) and surface air temperatures in NCEP
(Wiley, 2007) Tatlı, Hasan
In this study, synchronous linkages of the North Sea-Caspian pattern (NCP), associated with large-scale surface air temperature series selected from National Centers for Environmental Prediction-National Center of Atmospheric Research reanalysis (NCEP-NCAR) for the region over 50 degrees W- 120 degrees E and 0- 80 degrees N are investigated via teleconnection patterns based on phase synchronization. Phase synchronization is the process by which two or more cyclic systems (or subsystems) tend to oscillate with a repeating sequence of relative phase angles. Phase synchronization is usually applied to two waveforms of the same frequency with identical phase angles in each cycle. However, the notion of phase synchronization has been introduced as an extension of classical Huygens' synchronization in the case of interacting chaotic systems if there is an integer relationship of frequency, such that the cyclic systems share a repeating sequence of phase angles over consecutive cycles. The results of the phase synchronization method are compared with those of the classical cross-correlation method in cases in which cross-correlation method shows linear spatial cross-dependency, but the phase synchronization yields nonlinear spatial phase dependency. In the analyses, teleconnection patterns derived from phase synchronization are first calculated for raw and de-seasoned data (by removing periodic components in the surface air temperature series) in year-month scale and then for the data in seasonal-scale (namely, winter, spring, summer and autumn). Teleconnection patterns calculated by phase synchronization improve the experiential intra-phase relationships between the NCP Index (NCPI) and large-scale surface air temperature series, and ensures that the major modes of mid and high Northern Hemisphere variability in climate are characterized. Statistically significant phase synchronization patterns related to geopotential dipole heights of the NCPI extending over Greenland, the Balkans, Caspian Sea basin, eastern Mediterranean, Turkey and the Middle East, and further phase synchronization patterns over the circumpolar mode, which are utilized by phase interaction of Arctic oscillation (AO) with NCP, are obtained. In addition, significant phase synchronization patterns are also obtained over Tibetan plateau-Mongolia (Gobi Desert) interacting with the Siberian high, Asiatic monsoon and the intertropical convergence zone. Copyright (C) 2007 Royal Meteorological Society
Detrended cross-correlation patterns between North Atlantic oscillation and precipitation
(Springer Wien, 2019) Tatlı, Hasan; Menteş, Şükran Sibel
In this study, the long-range relationships between North Atlantic Oscillation (NAO) and precipitation data obtained from Climate Prediction Centre (CPC) Merged Analysis of Precipitation (CMAP) from 1979 to 2016 are investigated using Detrended Fluctuation Moving Average Cross-Correlation Analysis (DMCA). In the atmosphere, teleconnections through strong convective processes sporadically affect various climatic regimes in Europe, Mediterranean basin, North Africa, Middle East, and Caucasus. The NAO is one of the teleconnection processes and results in heavy rainfall in the Mediterranean basin during its negative phase while it gives rise to rain in Europe during its positive phase. The DMCA technique shows that the NAO fluctuation series exhibit different long-range cross-correlation coefficients, rho DMCA(s) with s being the moving average time window length, between the precipitation values and NAO. Large rho DMCA(s) coefficients with time window(s) larger than 12 months were obtained particularly over the Mediterranean basin, near the North Pole including northern Europe. Furthermore, the rho DMCA(s) coefficients were grouped into clusters using K-mean method to distinguish the similar patterns. The 1st cluster refers to the negative phase of the NAO indicating warm-rainy conditions and dry spells, which is especially evident in the Mediterranean basin. The 2nd cluster represents the long-range cross-correlation with respect to the positive phase of NAO and precipitation values, particularly for the Western and Northern Europe. Conversely, the 3rd cluster is evaluated as power law of long-range cross-correlations between the precipitation and NAO with respect to the different time scale processes.
Climatological evaluation of Haines forest fire weather index over the Mediterranean Basin
(Wiley, 2014) Tatlı, Hasan; Türkeş, Murat
Forest fires are the most crucial natural threat to forests and wooded areas. They destroy many more trees than all other natural catastrophes such as parasite attacks, insects, extreme weather events and others. Forest fires, especially in summer and dry autumn/spring periods, are frequent in the Mediterranean basin and represent growing environmental and ecological problems. The aim of this investigation is to determine a climatic pattern of fire-meteorology over the Mediterranean basin via the frequency analysis of the forest fires weather index (FFWI) of Haines. The FFWI values were obtained by using the hourly data derived from reanalysis fields available from the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) for the period 1980-2010. High frequency values of FFWI, taken to be a sign of moderate-level risk of forest fires, were obtained on the forests, scrubs, succulents and wooded areas in several countries facing the sea including Greece, Italy, Turkey, Syria, Lebanon, Cyprus, Macedonia, Albania, Serbia, Slovenia, France, Portugal, Spain, Morocco and Tunisia, almost all of which are characterized by dry summer, subtropical Mediterranean climates. As expected, the highest-level risk values are found in the arid desert climate regions: the desert areas of the Sahara and Libya in North Africa and the semi-arid steppe climate regions of the Middle East, as well as the semi-arid environments near the Caspian Sea basin.
Downscaling standardized precipitation index via model output statistics
(Centro Ciencias Atmosfera Unam, 2015) Tatlı, Hasan
This study investigates the possible impacts of future climate change on meteorological drought events in Turkey by using a new statistical downscaling technique based on polytomous logistic regression, denoted as the model output statistics (MOS) technique. It is designed to downscale the drought classes of the 12-month Standardized Precipitation Index (SPI). The main goal of a downscaling procedure is to determine the influences of large-scale climatic variability and the projected changes on the local scale-regional variables. The large-scale predictors used in this study were obtained from the output of the Second Generation Canadian Coupled General Circulation Model (CGCM2) simulations, run from 1940 to 2100 for three socioeconomic scenarios, namely control, with the constraint of the 20th century atmospheric concentration of greenhouse gases, and the SRES A2 and B2 scenarios. Observations from 96 meteorological stations were used to estimate 12-month SPI values for the period 1940-2010, leaving the last 10 years for validation against the results simulated by the CGCM2. The MOS results derived from the control climate simulation agree with the observed patterns for present climate. The MOS results derived from future climate scenarios lead to conclude that there is a decreased probability of very wet and extremely wet conditions. In addition, the probabilities of near-normal conditions will decrease in the Black Sea coast and will increase towards the Marmara Transition and continental eastern Anatolia regions.
Statistical complexity in daily precipitation of NCEP/NCAR reanalysis over the Mediterranean Basin
(Wiley, 2014) Tatlı, Hasan
This study investigates a deterministic index (I-D) for shaping regular coherent structures in meteorological and climatic variables. The developed I-D was applied to the large-scale daily precipitation series derived from the data sets of the reanalysis available from National Centres for Environmental Prediction/National Centre for Atmospheric Research for the period of 1950-2011 over the Mediterranean Basin. In order to show advantages and disadvantages of I-D, its results were compared with two other persistence indexes known in the literature. One of persistence index is estimated by using autocorrelation function (I-ACF), and the other is based on conditional probability (I-CP). Following the patterns of I-D, the low values are obtained over the countries facing the sea including Greece, Italy, Turkey, Syria, Lebanon, Cyprus, Macedonia, Albania, Serbia, Slovenia, France, Portugal, Spain, Morocco and Tunisia, almost all of which are characterized with dry summer subtropical Mediterranean climate. On the other hand, the meaningful climatic patterns of I-ACF are observed only over the Mediterranean Sea. At the same time as employing I-CP to wet state of the precipitation series, the same patterns are obtained as I-ACF. However, for dry state, I-CP produces noticeable similar patterns to I-D, generally in arid and semi-arid areas. The major results show that the patterns estimated by I-D could be better understandable in point of view of its representing traditional spatio-temporal meteorological features. That is, the patterns of I-D correspond to well-known climatic and weather features for large-scale daily precipitation values associated with influences of the atmospheric disturbances and physical geographical features such as topography and land-sea distribution over the Mediterranean Basin. Copyright (c) 2013 Royal Meteorological Society
Multivariate-drought indices-case studies with observations and outputs of NCAR CCSM-4 ensemble models
(Springer, 2021) Tatlı, Hasan
This study suggests developing a new drought index using the conditional probability of precipitation associated with a wide range of other weather variables, such as temperature, to monitor droughts. Once the marginal probability distributions of the variables become known, it is possible to determine the joint and conditional probabilities through the choice of suitable copula functions. This new drought index of the so-called conditional standardized precipitation index (CSPDI) allows for evaluation of droughts just like the standardized precipitation index (SPI). The L-Moment method was used in the application part of the study to estimate the marginal probabilities of temperature and precipitation; on the other hand, both French-Gumbel Morgenstein (FGM) and Gaussian copula types were used within the case studies to assess joint and conditional probabilities. To evaluate the potential of the proposed drought index, drought patterns were reviewed through this index across several climate zones obtained through the Holdridge Life Zone (HLZ) method. To demonstrate the proposed approach’s capabilities regarding climate change studies, the CSPDI has been applied to the production of the Community Climate System Model (CCSM-4) selected near the major provinces in the country that stand out in population, agriculture, and industrial development. In addition to this, the kriging interpolation technique has been used to embed temperature and precipitation variables recorded by the country’s meteorological stations within the same grid points as the CCSM-4 models. The spatial analysis of the drought patterns using the results of the CCSM4 models and the weather stations established at grid points in the vicinity of the five largest cities of the country provide a useful basis in terms of measuring drought conditions. All these results showed that the CSPDI results changed significantly according to the time characteristics; choosing the temperature as a secondary variable in the CSPDI calculation did not affect the drought model of a rainy weather station such as Rize. But in semi-arid regions such as Izmir and Antalya, both coastal regions, the temperature had a strong effect on drought patterns. Furthermore, the suggested methodology has been applied to the results of GCM models used with CCSM-4 built on the RCP 8.5 scenario. The precipitation and temperatures used in the CSPDI calculations were derived from the NCAR GIS climate model, which allowed the IPCC to apply the CCSM-4 simulation methods in the fifth assessment of the AR5 report.
Climate classification in Turkey: a case study evaluating Holdridge life zones
(Springer, 2021) Tekin, Mehmet Kadri; Tatlı, Hasan; Koç, Telat
The Holdridge life zone (HLZ) method is applied to map potential vegetation types in Turkey. The HLZ map is compared to a map of actual vegetation in order to assess the degradation status of vegetation in Turkey. Data required to identify HLZ classes are provided by the General Directorate of Meteorology, while the current vegetation status is estimated with data provided by the General Directorate of Forestry. After weather data are cleaned and missing values are replaced, the HLZ type is estimated for each station, and then thematic maps are created using the ArcGIS software. The study reveals that there are 12 HLZ types in Turkey. The three dominant types are as follows: cool temperate steppe, warm temperate dry forest, and cool temperate moist forest. In regions where physical geographical controls change in short distances, the biodiversity is greater, and linked to this, the HLZ diversity also appears to be greater. Comparing the identified life zones to the actual vegetation, in some areas, remarkable mismatches can be found. Although, in some regions, the life zone type is consistent with the land cover type, in some narrow areas, the potential vegetation does not reflect features of the current vegetation cover. Considering limitations and capabilities of the assessment approach used in this study, we think that the incompatibility between actual and modelled vegetation types in the eastern region of Turkey is caused by the intensive landscape use. The goal of this research is to support future bioclimatic studies and land use management strategies.
Analysis of temporal diversity of precipitation along with biodiversity of Holdridge life zones
(Springer, 2021) Tatlı, Hasan; Dalfes, H. Nuzhet
Many ecological studies show that diversity of vegetation is generally sensitive to hydrometeorological variables such as temperature, precipitation, and evaporation. Furthermore, it is also known that there have been changes in the precipitation regimes due to climate change and/or land use (such as urbanization). This study investigates the temporal diversity of the precipitation along with the Holdridge life zones (HLZ) using the biodiversity indices of true Hill numbers and Rényi entropy. The results show that there are no statistically significant changes in the “biodiversity” with respect to the HLZ. However, it was found that, although the biodiversity has remained more or less stable through 45 years, the HLZ classes have widened toward much warmer and drier vegetation cover. One can propose that the water regime of the rivers of the country has also changed due to the early melting of snow and an increase in evapotranspiration as a result of warming. Furthermore, using the Gini-Simpson diversity index for daily rainfall types recorded in a spatially homogeneous manner over Turkey, one can show that there are no significant changes in rainfall diversity in the coastal regions, but significant changes are observed in the internal and relatively high-altitude areas of the country.
Analysis of drought intensity, frequency and trends using the spei in Turkey
(Springer, 2023) Serkendiz, Hıdır; Tatlı, Hasan; Kılıç, Ayşegül; Çetin, Mahmut; Sungur, Ali
This study addresses into the critical issue of drought as a natural disaster, especially in regions characterized by arid and semi-arid climates like Turkey. The primary aim of this study is to investigate the historical occurrences of meteorological drought events in Turkey, focusing on their past frequency, intensity, and spatial distribution. The study employs the Standardized Precipitation Evapotranspiration Index (SPEI) method and utilizes 50 years of monthly temperature and precipitation data collected from 222 meteorological stations across the country. Drought severity is assessed using the run theory method, and trends in drought patterns are analyzed through the Mann–Kendall trend test. Additionally, the text explores the connection between elevation and the geographical distribution of drought events. The study’s findings reveal a noticeable increase in the occurrence of drought periods over time. Among the selected periods, the most widespread drought event was observed in the year 2001. The Bozcaada meteorology station exhibited the highest frequency of drought with a value of 223, while the Ispir meteorology station recorded the lowest frequency with a value of 151. Over the course of the 50-year analysis, no significant correlation was found between drought and elevation, although a gradual increase was noted in the last 10 years. The results also indicate a gradual north-to-south increase in drought intensity in Turkey. The study identifies four distinct drought hotspots in the country: the Western Anatolia Region, Central and Southern Anatolia Region, Southeastern Anatolia Region, and Eastern Anatolia Region.

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