Effects of urbanization and land-use type on monthly extreme temperatures in a developing semi-arid region, Turkey

Climate change is a great concern and attracted attention of many researchers in the world. A study was conducted to determine the effects of regional parameters such as population change (Delta P), number of motor-driven vehicles (NMDV), area covered by industrial crops (A), number of buildings (NB), and monthly extreme temperature trends in a developing semi-arid southeast region of Turkey, known as GAP area. Monthly extreme temperature series observed at 16 observation stations, covering the period of 1932-2002, with record length varying between 27 and 71 years, were utilized. Nonparametric Mann-Kendall test procedure was employed to detect monthly trends. Multiple and univariate linear regression analysis were employed to relate Mann-Kendall test statistic Z to the regional parameters. Spatial coverage maps of statistically significant upward and downward trends for each month were produced by using inverse distance squared weighting (IDSW) method. The most widespread upward trend was determined in January and July covering 42.9% and 40.9% of total area for maximum (T-max) and minimum (T-min) temperatures. There were no statistically significant (P <= 0.05) downward trends for extreme temperature series in the area studied. Multiple regression analysis (overall model) results revealed that determination coefficients for T-max and T-min were the highest as 94.0% in August and 87.8% in June. Univariate regression analysis led us to conclude that Delta P and A were the most important parameters to detect trends in T-min and T-max series. Mann-Kendall test statistic Z for T-max in summer time was negatively correlated with A. This was likely due to direct human influence through irrigation practices as well as the construction of large man-made water bodies in the region. The Delta P, NMDV, and NB were positively correlated with T-min, indicating that the cool period is gradually becoming warmer with time. We concluded that, as the area sown with industrial crops increases, there is a decrease in maximum temperatures due to the evaporative cooling mechanism. Increase in urbanization and/or industrialization, causes an increase in minimum temperatures in the area. (c) 2006 Elsevier Ltd. All rights reserved.