Extreme value analysis and forecasting of maximum precipitation amounts in the western Black Sea subregion of Turkey

Monthly maximum precipitation amounts for the period 1950-2010 were modelled for seven climatological stations in the western Black Sea subregion of Turkey using a distributional and time series analysis approach. First, the generalized extreme value (GEV) distribution was fitted using the location parameter of the GEV distribution as a function of several explanatory variables that affect the maximum precipitation. We quantified the change in extreme precipitation for each location and derived estimates of return levels for monthly precipitation amounts. We also considered a multivariate time series model with exogenous variables using the selected locations for a short-term forecast of the maximum precipitation amount. It was discovered that the time series model that takes into account the autocorrelation structure of the series performed better than a probabilistic approach using the extreme value theory. The obtained forecast results are promising in terms of accurately defining future precipitation amounts

Projections of climate change in the Mediterranean Basin by using downscaled global climate model outputs

The Mediterranean Basin is one of the regions that shall be affected most by the impacts of the future climate changes on hydrology and water resources. In this study, projected future changes in mean air temperature and precipitation climatology and inter-annual variability over the Mediterranean region were studied. For performing this aim, the future changes in annual and seasonal averages for the future period of 2070-2100 with respect to the period from 1970 to 2000 were investigated. Global climate model outputs of the World Climate Research Program's Coupled Model Intercomparison Project Phase 3 multi-model dataset were used in this work. Intergovernmental Panel on Climate Change SRES A2, A1B and B1 emission scenarios' outputs were used in future climate model projections. Future surface mean air temperatures of the larger Mediterranean basin increase mostly in summer and least in winter, and precipitation amounts decrease in all seasons at almost all parts of the basin. Future climate signals for air temperature and total precipitation values are much larger than the inter-model standard deviation. Inter-annual temperature variability increases evidently in summer season and decreases in the northern part of the domain in the winter season, while precipitation variability increases in almost all parts of domain. Probability distribution functions are found to be shifted and flattened for future period compared to the reference period. This indicates that the occurrence of frequency and intensity of high temperatures and heavy precipitation events will likely increase in the future period

Shallow and deep-seated regolith slides on deforested slopes in Canakkale, NW Turkey

This 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

Evaluating the effects of different beverages with daily consumption habits on the wear of restorative materials

The aim of this study was to investigate the cumulative effects of fruit juices and/or alcoholic beverages on wear track area of the restorative materials by simulating the oral environment in vitro. A microhybrid, a sub-microhybrid, a nanofill resin composite, and a giomer material were used. A daily exposure habits model was created to simulate consumption frequency of acidic and/or alcoholic beverages. Two-body wear tests were carried out using a reciprocating wear tester. ANOVA and Tukey's HSD tests were used for statistical analyses (p < 0.05). When considering experimental groups related to daily exposure habits, statistical difference was found between restorative materials in terms of wear track area (p < 0.01). Joint effect of rmaterial and exposure on wear track area was statistically significant (p < 0.01). Giomer was found to be more affected by acidic and alcoholic beverages. Microhybrid resin composites showed less wear than the other restorative materials. Cumulative effects of alcoholic beverages and fruit juice on wear track area of materials could be related to material's composition and frequency of consumption of acid or ethanol-containing beverages. Daily cumulative effect of acidic and alcoholic beverages was found to be stronger than only acidic fruit juice consumption in terms of wear track area. The plasticizing effect and the concentration of ethanol in the alcoholic beverages provided the basis for the increased wear track area on the restorative materials

Geomorphological investigation of the excavation-induced Dundar landslide, Bursa, Turkey

This 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

Has the climate been changing in Turkey? Regional climate change signals based on a comparative statistical analysis of two consecutive time periods, 1950-1980 and 1981-2010

In this study, the climate zones of Turkey were re-examined using different objective statistical tests based on the differences in the behaviour of meteorological variables, and a comparative analysis of 2 consecutive periods was performed statistically. The data consisted of total precipitation, and minimum, maximum and mean air temperature series recorded from 1950-2010 at 244 climatological/meteorological stations operated by the Turkish Meteorological Service. K-means and hierarchical clustering methods were applied separately to each variable to obtain surface air temperature and precipitation patterns in Turkey for the periods of 1950-1980 and 1981-2010. Paired-samples Student's t-test (paired t-test) and Pitman-Morgan (P-M) t-test were used to detect possible changes in the mean and variance of the series in the transition from one period to the other. The results of the analysis reveal that the climate characteristics of Turkey are generally similar for the temperature series under study. However, there are some changes in the existing geographical patterns of the climate regions. Statistical tests show that all 3 air temperature series increased after 1980. The major changes appeared in the precipitation regions of Turkey: there were significant changes in the continental central, central-west and central-east Anatolia regions, and in the continental north and eastern Anatolia region. It was also apparent that precipitation amounts increased in the northern and eastern regions of Turkey after 1980, but amounts decreased in the west, central and southern regions, most of which are generally characterized as having a dry summer subtropical Mediterranean climate

Clustering current climate regions of Turkey by using a multivariate statistical method

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