Assessing the effects of urban green landscape on urban thermal environment dynamic in a semiarid city by integrated use of airborne data, satellite imagery and land surface model

Abstract

The response of the urban thermal environment to green space landscapes has been studied previously, while its detailed pattern is insufficiently explored owing to the constraints of spatial and temporal resolution of available datasets. This study uses integrated Thermal Airborne Spectrographic Imager (TASI) data, Landsat TM/ETM and MODIS satellite imagery, and Noah land surface model output to investigate the effects of landscape pattern on the urban thermal environment across Shijiazhuang, China. The present study not merely proposes a generalized framework for the spatiotemporal analysis of urban thermal environment, but also affords several insights into the cooling effects related to urban green space landscapes in semiarid cities. Firstly, trees and lawns show a noticeable disparity in land surface temperature (LST) response to urban green landscape metrics, primarily due to the difference in cooling efficiency via evapotranspiration. This disparity can be explained further by the radiation-shading effect of trees. Secondly, analysis confirms that the composition of urban green space has a substantial impact on LST throughout summer. This pattern is largely stable for trees owing to the constant Bowen ratio, but they are altered for lawns. Conversely, the configurations of urban green space exhibit less impact on LST. These effects vary temporally in magnitude and can be enhanced notably in humid conditions. The lower correlation between the configuration metrics of urban green and LST has to do with the surface resistance alterations and additional cooling effects. Finally, consistent patterns of the impact of urban green space landscape metrics on LST are illustrated at different spatial scales and region sizes but greater effects are revealed for smaller analytical units, further confirming the impacts of urban green landscape on urban thermal environment.