Detection of atmospheric urban heat island through direct measurements in Cluj-Napoca city, Romania

Abstract

In the last decades, cities worldwide have experienced accelerated development, so that continuous urbanization and its impact is presently one of the most important topics in different fields of research. The main aim of this study is to identify the intensity of the atmospheric urban heat island in Cluj-Napoca city, through direct observations campaigns by using fixed points and transect measurements. The data has been collected over a period of 6 months (May-October 2015). The measurements have been performed mainly in anti-cyclonic weather condition, during the night, between 23:00 and 03:00. The profiles trajectories followed the main roads of the city on directions North-South, East-West, and Northwest-Southeast. 8 fixed points have been chosen in order to highlight best the temperature patterns in different Local Climate Zones (LCZs). The main findings of the study are the followings: the direct observations performed in three seasons (spring, summer and autumn) revealed the existence of an atmospheric urban heat island in Cluj-Napoca city; the warmest areas are compact high-rise and compact midrise, located in the eastern half of the city, where the temperature increases by more than 2.0 °C, as average value for all campaigns, but the maximum values, recorded in the summer are higher than 3.0 °C; the coolest areas are sparsely built areas and the large low-rise/water areas, where the temperature is quite similar to that recorded in the nearby rural areas (diff erence of 0.0-0.1 °C, as average values); local factors, such as mountain breeze and topography have a great impact on the atmospheric urban heat island configuration.