Experimental evidence of the multiple microclimatic impacts of bushfires in affected urban areas: the case of Sydney during the 2019/2020 Australian season

Abstract

Abstract This paper presents the results of a monitoring campaign conducted in the inner west of the city of Sydney during the 2019/2020 bushfire season. The combined effects of extreme pollution, heat waves and droughts are analyzed in terms of microclimatic perturbation. A compact meteorological station measured air temperature, relative humidity, barometric pressure, precipitation, wind (speed and direction), solar radiation, UV radiation, UV index, PM1, PM2.5 and PM10, at the one site. The monitoring campaign lasted from the 20th of December 2019 to the 13th of January 2020, when hundreds of bushfires were ravaging the bordering areas. A suite of dependencies emerged between PM concentration and air temperature, relative humidity, wind speed and rain. PM concentration was higher during the night and in the morning, especially after daytime overheating events (temperature above 35 °C). Raindrops triggered the highest and most persistent dust levels. Dense layers of PMs, in turn, strongly attenuated the UV radiation. Collected data also indicated anomalies in the intensity of the urban heat island compared to historical trends. This study is a first attempt to link together several different parameters on a local scale under weather anomalies. Future efforts will be directed to strengthening the validity of the above results and approach to broader boundary conditions.