Exploring the Synergies between Urban Overheating and Heatwaves (HWs) in Western Sydney

Abstract

There is no consensus regarding the change of magnitude of urban overheating during HW periods, and possible interactions between the two phenomena are still an open question, despite the increasing frequency and impacts of Heatwaves (HW). The purpose of this study is to explore the interactions between urban overheating and HWs in Sydney, which is under the influence of two synoptic circulation systems. For this purpose, a detailed analysis has been performed for the city of Sydney, while considering an urban (Observatory Hill), in the Central Business District (CBD), and a non-urban station in Western Sydney (Penrith Lakes). Summer 2017 was considered as a study period, and HW and Non-Heatwave (NHW) periods were identified to explore the interactions between urban overheating and HWs. A strong link was observed between urban overheating and HWs, and the difference between the peak average urban overheating magnitude during HWs and NHWs was around 8 °C. Additionally, the daytime urban overheating effect was more pronounced during the HWs when compared to nighttime. The advective flux was found as the most important interaction between urban overheating and HWs, in addition to the sensible and latent heat fluxes.

Synergies between urban heat island and heat waves in Seoul: The role of wind speed and land use characteristics

“…Also, the observed higher AH between HW and NHW period is consistent with previous studies [27] and is attributed to the increased temperature during HW periods that enhance evapotranspiration mechanisms, ultimately resulting in increased atmospheric water content during HW periods. At the same time, AH levels were relatively higher at the rural station than the urban stations during both HW and NHW periods.…”

“…This threshold can be defined as an absolute temperature value or relative temperature value considering mean or maximum daily temperature distributions within a given period (e.g., 95 th , 97 th percentiles). Both of these approaches are widely adopted in the literature [27,43]. In this study, we define a HW episode as a period of three or more consecutive days when T max > 33˚C.…”

“…They found increased UHI magnitudes of up to 3.5˚C during HW periods compared to ordinary summer conditions. Similarly, Khan et al [27] explored UHI magnitudes during HW and NHW periods in Australia. They found UHI levels in HW periods higher than those in NHW periods by a magnitude of 8˚C.…”

“…While the synergistic interactions between UHI and HWs have been studied, to an extent, in some large cities around the world which are discussed above [26][27][28][29], it is essential to remark that the synergies between UHI and HW are likely to be influenced by factors (e.g., synoptic weather, topography, population density, land use) specific to a given region/city. As such, the synergies between UHI and HW within a given area are distinctive rather than general and must be quantified for individual areas of interest.…”

Urban Morphological Controls on Surface Thermal Dynamics: A Comparative Assessment of Major European Cities with a Focus on Athens, Greece

“…Besides the central role of urban morphology discussed above, sea breeze has also been found to be an important determinant of the urban heat island intensity, usually exerting a strong moderating influence [101][102][103]. To include the effects of the sea breeze in the current statistical analysis, further regression models were developed incorporating the proximity to the sea-the distance between the center of a given image pixel and the coastline (d)-as an additional independent variable.…”