We investigated the usage of high-resolution satellite data to conduct urban climate studies. The main objectives of this research is to: 1) Develop cutting-edge satellite technology and generate freely available high-quality urban morphology information from high-resolution satellite data; 2) Provide urban climatic maps for developing countries without actual urban
morphology information; 3) Using high-resolution satellite images to assess urban wind ventilation and urban thermal environment; 4) Provide data-based early warning of high-risk urban areas with adverse urban climate issues.
The completed works include as the following:
1. Urban morphology extraction (Figure 1)
A new satellite technology has been developed to extract 3D urban morphology by using World-view-2 stereo satellite images and Terra-SAR images. The benefit of the proposed approach is that the advantages of both stereo and SAR images are well combined, as SAR images are good at predicting the heights of tall buildings while stereo images can provide the complementary height information of buildings for which SAR is missing. Experimental results showed that the overall prediction accuracy is about 80-90%. (Details are provided in the references [1-2])
Figure 1. The retrieved 3D building information from satellite data using our proposed approach. (a) Satellite-derived 3D model. (b) Actual 3D model for comparison.
2. Validation of satellite-derived morphological parameters for urban climate studies (Figures 2)
A set of urban morphological parameters were calculated based on satellite-derived building morphology. Five most widely used urban morphological parameters—building coverage ratio (BCR), building volume density (BVD), frontal area index (FAI), sky view factor (SVF), and roughness length (RL) —were validated with high prediction accuracy.
Impacts of satellite-derived morphological parameters on urban air temperature and urban ventilation at pedestrian level were investigated, and empirical relationships between satellite-derived morphological parameters and urban climate (e.g., urban air temperature difference and wind dynamics) were built. In this study, the physically based simulation model parallelized large-eddy-simulation (LES), was used to test the impact of satellite-derived morphological parameters on pedestrian-level wind ventilation, while the WOLWEIG-model, developed by Göteborg Urban Climate Group, was used to test their impact on the mean radiant temperature.
Figure 2. Urban ventilation simulations at pedestrian level using (a) Satellite-derived model. (b) Actual 3D model.
3. Quantitative urban climate mapping using satellite data (Figure 3) Based on the empirical relationships between satellite-derived morphological parameters and urban climatic environments, an urban climate map can be generated from the satellite-derived morphological parameters.
Figure 3. Urban climatic maps generated from (a) Actual GIS data. (b) Satellite data
References
1. Xu, Y., Ma, P., Lin, H., & Ng, E., 2015. Fusion of World-view2 stereo and TerraSAR-X images for 3D building extraction in high-density urban areas. 9th International Conference on Urban Climate (ICUC 9), France, July 20-24, 2015.
2. Xu, Y., Ma, P., Ng, E., & Lin, H. 2015. Fusion of WorldView-2 Stereo and Multi-temporal TerraSAR-X Images for Building Height Extraction in Urban Areas. IEEE Geoscience and Remote Sensing Letters, 12(8), 1795-1799.