Does the arrangement of urban greenspace matter for air temperature?

Details

Optimizing the spatial pattern of urban greenspace—both its composition and configuration—can alleviate the urban heat island effect. While the relationship between air temperature and greenspace composition has been widely studied, this study investigated its relationship with greenspace configuration, including variations by time of day and spatial scale.

The researchers used hourly air temperature data from 36 meteorological stations in Changsha, China, and land cover data interpreted from Gaofen 2 remote sensing images. Around each air station, they measured greenspace composition as the percentage of greenspace and configuration as average patch area, patch density, edge density, landscape shape index and mean shape index, using buffers from 30 m to 2000 m. They analyzed Pearson correlations between air temperature and each landscape metric, and partial Pearson correlations between air temperature and configuration metrics while controlling for greenspace percentage. Multiple linear regression modeled air temperature variation using the landscape metrics as independent variables. Variance partitioning analysis assessed the relative importance of composition and configuration in explaining that variation.

The temperature range reached 1.73 °C during the day and 2.94 °C at night. Urban greenspace was fragmented, especially at small scales. The Pearson correlation between air temperature and greenspace percentage fluctuated as scale increased and was generally higher during the day than at night.

Greenspace spatial patterns explained up to 55% of air temperature variation, with differences by time of day and scale: the maximum was 0.54 during the day at a 50 m buffer and 0.55 at night at a 400 m buffer. A higher percentage of greenspace, more aggregated patches and simpler shapes were associated with stronger cooling. The relative importance of composition and configuration also varied across spatial scales and between day and night.

The findings emphasize both scale effects and day–night variation in the relationship between greenspace patterns and air temperature. The authors say they provide theoretical guidance for greenspace planning and management to improve the urban thermal environment in rapidly developing subtropical cities such as Changsha.