Climate change and its urban-induced bias in selected Turkish cities is studied with a quality controlled temperature and precipitation data of Turkish stations in the period of 1950-2004. These stations are classified into two groups according to their populations; S1, including rural and suburban stations and S2, including large urban stations. Moving average signals, 365-day, and their digital low pass filtered versions are produced to eliminate the short term fluctuations and examine the possible trends or anomalies in climate data. Furthermore, 'relative difference' signals are introduced and applied to temperature and precipitation series to observe the actual local changes in the climate data independent from largescale effects. Mann-Kendall test statistics are calculated for maximum, minimum, mean temperature and precipitation series and plotted on maps to determine any spatial trend patterns. Signal analysis show a cool period extending from early 1960s till 1993, generally with the lowest temperature values on 1992-1993 owing to the eruption of Mount Pinatubo. A last decade significant warming trend is observed in both of the series, S1 and S2, leading to 2000-2002 temperatures to be recorded as Climatic Change (2009) 94:483-502 maximums in record history. The variability of urban precipitation series is generally larger than the rural ones, suggesting that urban stations can experience more frequent and severe droughts and floods. Though not significant, an increase in the urban precipitation compared to the rural one is also found. Spatial analysis resulted in significant warming in southern and southeastern parts of the country. Particularly, minimum temperature series show significant warming in almost all of the regions indicating the effect of urbanization. Significant decreases of precipitation amounts in the western parts of Turkey, such as Aegean and Trachea regions, are found. On the other hand, some Turkish northern stations show increases in precipitation of which some are significant.

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In this study a set of cyclone frequency statistics is developed and the prevailing tracks of cyclones are derived for a region of the world that has not been previously investigated in detail. Analysis reveals that Turkey experiences the effects of five dominant cyclone trajectories. Investigation of the seasonal variability of the cyclone frequencies shows that the highest number of cyclones occurs during winter. The variability of the subtropical jetstream latitude is analysed by multi-variable regression involving cyclone numbers, the numbers of occurrences of the Mediterranean Persistence High Pressure (MPHP), which is an extension of the Azore High Pressure and their periods. This analysis revealed that the most important factor among the three factors chosen is the number of observed blocking cases over Turkey. Although the northern parts of Turkey are accepted as having a transitional type climate between the Mediterranean and temperate regions, our results showed that they are more influenced by cyclones of Mediterranean origin.

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Abstract. With a view to estimating climate change and its urban-induced bias in selectedaverage result for the two grid points located over Turkey.

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