Urban Heat Island and Overheating Characteristics in Sydney, Australia. An Analysis of Multiyear Measurements

It has become increasingly important to study the urban heat island phenomenon due to the adverse effects on summertime cooling energy demand, air and water quality and most importantly, heat-related illness and mortality. The present article analyses the magnitude and the characteristics of the urban heat island in Sydney, Australia. Climatic data from six meteorological stations distributed around the greater Sydney region and covering a period of 10 years are used. It is found that both strong urban heat island (UHI) and oasis phenomena are developed. The average maximum magnitude of the phenomena may exceed 6 K. The intensity and the characteristics of the phenomena are strongly influenced by the synoptic weather conditions and in particular the development of the sea breeze and the westerly winds from the desert area. The magnitude of the urban heat island varies between 0 and 11C, as a function of the prevailing weather conditions. The urban heat island mainly develops during the warm summer season while the oasis phenomenon is stronger during the winter and intermediate seasons. Using data from an extended network of stations the distribution of Cooling Degree Days in the greater Sydney area is calculated. It is found that because of the intense development of the UHI, Cooling Degree Days in Western Sydney are about three times higher than in the Eastern coastal zone. The present study will help us to better design and implement urban mitigation strategies to counterbalance the impact of the urban heat island in the city.