The urban heat island of Bucharest during the extreme high temperatures of July 2007

This paper explores the characteristics of the air (T-air) and land surface temperature (LST) from the city of Bucharest (Romania) during the extreme high temperatures that affected the region in July 2007. The behavior of Bucharest's Urban Heat Island (UHI) is quantitatively described following similar methodological approaches to previous studies. The analysis integrates thermal data supplied by the Moderate Resolution Imaging Spectroradiometer (MODIS) sensors aboard the NASA satellites and meteorological data provided by the ground-based weather stations. Based on the T-air, one may claim that during extreme high summer temperatures, the UHI preserves its spatial and temporal pattern regarding the differences between the central urban perimeter and the suburban area. The investigation of the LST from July 2007 reveals that the nocturnal changes refer mainly to the magnitude and the limits of the UHI, while the shape is not changed. However, the extreme temperatures induce significant modifications of the features of the diurnal UHI, obliterating and dissipating it in certain spots, enlarging it and creating shifted heat islands in some other spots. The main explanation is the outstanding duration and intensity of the hot mass of air impacting the area. The correlations between the T-air measured at the weather stations in Bucharest and the corresponding LST retrieved significant values both under "normal" conditions and extreme temperature persistence, and offer good premises for robust validation studies. The MODIS products performed like an extremely useful instrument for analyzing the UHI.