Picture: Sydney looking west from the air. Credit: Mudassir Ali (Pexels).

Variability in urban land-use results in microclimatic variability across a city that is not picked up by government weather station networks. Crowdsourced weather stations can fill these gaps.

CLEX researchers and colleagues used crowdsourced data from over 500 citizen weather stations during summer in Sydney, Australia, combined with detailed land-use data to explore how air temperature varies across the city. Sydney is a complex environment due to its proximity to the ocean, mountainous topography, and diverse urban land use.

The crowdsourced data consists of 2.3 million data points that were quality controlled and compared with reference data from five Bureau of Meteorology weather stations. Crowdsourced stations measured higher night-time temperatures, higher maximum temperatures on warm days, and cooler maximum temperatures on cool days. These differences are likely due to the influence of urban materials and activities close on the crowdsourced weather stations which are often located in backyards.

The distance from the coast and spatial variability in urban land-use and land-cover influenced spatial variability in urban temperatures. Crowdsourced temperatures at night-time were particularly sensitive to surrounding land cover, with lower temperatures in regions with higher vegetation cover, and higher temperatures in regions with more impervious surfaces.

Crowdsourced weather stations provide highly relevant data for health monitoring and urban planning, however, there are several challenges to overcome to interpret this data, including an uneven distribution of stations with a possible socio-economic bias. However, the sheer number of crowdsourced weather stations available can provide a high-resolution understanding of the variability of urban heat that is not possible to obtain via traditional networks.

Paper: Potgieter Julia, Nazarian Negin, Lipson Mathew J, Hart Melissa A, Ulpiani Giulia, Morrison William, Benjamin Kit (2021): Combining High-Resolution Land Use Data With Crowdsourced Air Temperature to Investigate Intra-Urban Microclimate. Frontiers in Environmental Science.https://doi.org/10.3389/fenvs.2021.720323