According to the United Nations estimations about half of the world population live in urban areas by the end of the second millenium, and the ratio will tend to increase. The large number of people and the socio-economic conditions produce high industrial activity. Consequently, consumption of energy and other raw material are constantly increasing. In order to find potential mitigation strategies that facilitate the urban population to adapt to new environmental conditions urban heat islands and other climatological impacts of urbanization must be investigated. In our study we provide detailed comparison of the urban heat island effects for the Budapest agglomeration area (capital of Hungary) and other large cities of the Carpathian Basin. A new approach has been applied, namely satellite images have been applied as a basic tool to the present analysis.

Part of the NASA's Earth Observing System satellite TERRA was launched to a polar orbit in December 1999. This program plays an important role in development of validated, global, interactive Earth system models being able to predict global change accurately. In our research measurements of two satellite sensors of the five on-board instruments have been used to analyze surface temperature of urban areas in the Carpathian Basin. (1) Moderate Resolution Imaging Spectroradiometer (MODIS) is capable of viewing the entire globe daily with 1 km resolution. (2) Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) has very fine spatial resolution (90 m per pixel). First validated observations of TERRA started in February 2000, and regular measurements are available from July 2000.

In our investigation daytime and nighttime surface temperature time series measured in the Carpathian Basin have been analyzed. First, the largest cities have been selected and the pixel representations of urban areas and their rural environment have been determined. Our results suggest that intensity of the urban heat island detected in Hungarian cities ranges between 1 K and 3 K, the most intense periods include the summer season and nighttime. Then, using the selected representative area of Hungarian cities we have determined spatial structures of the urban heat island depending on seasons and different macrocirculation conditions. Further analysis have been carried out by identifying special pixels according to the characteristical surface cover (concrete buildings, parks, residential areas, airports, etc.) and evaluate the time series of surface temperature observed by MODIS and ASTER. Finally, satellite and ground based observations have been compared. Special analysis technique is needed and has been applied since regularly observed temperature by meteorological services is measured at 2 meter height in sheltered white box, while satellite data sets are representatives of surface conditions.