Experimental evidence of the multiple microclimatic impacts ofbushfires in affected urban areas: the case of Sydney during the2019/2020 Australian season

Giulia Ulpiani,
Gianluca Ranzi and Mat Santamouris

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

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