Analysis of urban effects on soil temperature in Ankara

In this study, data from two different meteorology stations were analyzed in order to reveal the effects of the urbanization on the soil temperature. These stations are the Ankara Meteorology Station (AMS), showing the urban effects, and the Esenboğa Meteorology Station (EMS), showing the rural effects. The soil temperatures measured at depths of 5, 10, 20, and 50 cm at 0700, 1400, and 2100 hours between 1960 and 2005 were used in the analysis. Long-term mean monthly temperatures at each depth and at each time considered were calculated and analyzed using Sen's slope and Mann-Kendall tests. The results showed that the mean monthly urban soil temperatures were generally higher than the rural soil temperatures. The differences between temperatures measured at 5, 10, 20, and 50 cm in urban and rural stations (DeltaT(s(AMS-EMS))) ranged between 1.8 degrees C and 2.1 degrees C. As in the urban heat islands, the differences between the urban and rural soil temperatures are high at 2100 hours and low at 1400 hours. It was also observed that, due to the increasing number of buildings around the Esenboğa Station in recent years, the difference between the urban and rural soil temperatures seems to have become smaller. These show that the factors affecting the urban heat islands and those affecting the soil temperatures are similar. Also, the temperature differences were observed to be higher during the warm season than in the cold season. The frequency distributions of the temperature differences (DeltaT(s(AMS-EMS))) reveal both positive and negative values. However, the positive temperature differences are obviously prevalent.