Climate zones of Turkey are redefined by using the mathematical methodology of cluster analysis. Data from 113 climate stations for temperatures (mean, maximum and minimum) and total precipitation from 1951 to 1998 are used after standardizing with zero mean and unit variance, to confirm that all variables are weighted equally in the cluster analysis. Hierarchical cluster analysis is chosen to perform the regionalization. Five different techniques were applied initially to decide the most suitable method for the region. Stability of the clusters is also tested. It is decided that Ward's method is the most likely to yield acceptable results in this particular case, as is often the case in climatological research. Seven different climate zones are found, as in conventional climate zones, but with considerable differences at the boundaries.
Changes in temperature due to variability in meteorology and climate change are expected to significantly impact atmospheric composition. The Mediterranean is a climate sensitive region and includes megacities like Istanbul and large urban agglomerations such as Athens. The effect of temperature changes on gaseous air pollutant levels and the atmospheric processes that are controlling them in the Eastern Mediterranean are here investigated. The WRF/CMAQ mesoscale modeling system is used, coupled with the MEGAN model for the processing of biogenic volatile organic compound emissions. A set of temperature perturbations (spanning from 1 to 5 K) is applied on a base case simulation corresponding to July 2004. The results indicate that the Eastern Mediterranean basin acts as a reservoir of pollutants and their precursor emissions from large urban agglomerations. During summer, chemistry is a major sink at these urban areas near the surface, and a minor contributor at downwind areas. On average, the atmospheric processes are more effective within the first 1000 m above ground. Temperature increases lead to increases in biogenic emissions by 9±3% K<sup>−1</sup>. Ozone mixing ratios increase almost linearly with the increases in ambient temperatures by 1±0.1 ppb O<sub>3</sub> K<sup>−1</sup> for all studied urban and receptor stations except for Istanbul, where a 0.4±0.1 ppb O<sub>3</sub> K<sup>−1</sup> increase is calculated, which is about half of the domain-averaged increase of 0.9±0.1 ppb O<sub>3</sub> K<sup>−1</sup>. The computed changes in atmospheric processes are also linearly related with temperature changes
Abstract:Statistical and numerical modeling tools were used to investigate the climatic effects of urbanization in Istanbul, the largest city in Turkey. Mann-Kendall trend test was applied to minimum temperature data from stations located in urban, suburban and rural areas in Istanbul to determine the existence and significance of trends, and the approximate years in which changes in the trends started. In addition, using a mesoscale atmospheric model, a sensitivity experiment was carried out to explore the atmospheric effects of urbanization in the city. Both statistical and modeling analyses indicated significant warming in the atmosphere over the urbanized areas. Mann-Kendall tests indicated statistically significant positive trends in the time series of the differences in minimum temperatures between urban and rural stations. Seasonal analyses showed that the urbanization effect on climate was most pronounced in summer. In most cases, the changes in the trends occurred in the 1970s and 1980s when the population growth rate in Istanbul increased dramatically. The model results exhibited a significant expansion of the urban heat island in Istanbul from 1951 to 2004, fairly consistent with the expansion of the city in this period. A two-cell structure for the urban heat island emerged at the reference level from the difference of the July simulations with current and past landscapes: one on the European side and the other on the Asian side of the city. The maximum reference-level temperature difference between the past and present simulations was found to be around 1°C. The modeling experiment also indicated that the velocity of the prevailing northeasterly wind and the water vapor mixing ratio were both reduced over the city. The heating effect due to urbanization was found to penetrate about 600-800 m height in the atmosphere over the city, and the two surface heat island cells were found to combine aloft.
We developed a high quality reconstruction of May-June precipitation for the interior region of southwestern Turkey using regional tree-ring data calibrated with meteorological data from Burdur. In this study, three new climate sensitive black pine chronologies were built. In addition to new chronologies, four previously published black pine chronologies were used for the reconstruction. Two separate reconstructions were developed. The first reconstruction used all site chronologies over the common interval AD 1813-2004. The second reconstruction used four of the chronologies with a common interval AD 1692-2004. R² values of the reconstructions were 0.64 and 0.51 with RE values of 0.63 and 0.51, respectively. During the period AD 1692-1938, 41 dry and 48 wet events were found. Very dry years occurred in AD 1725, 1814, 1851, 1887, 1916, and 1923, while very wet years occurred in AD 1736, 1780, 1788, 1803, and 1892. The longest dry period was 16 years long between 1860 and 1875. We then explored relationships between the reconstructed rainfall patterns and major volcanic eruptions, and discovered that wetter than normal years occurred during or immediately after the years with the largest volcanic eruptions.
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