Spatial-temporal Changes Of The Impervious Surface And Its Impacts On The Urban Thermal Environment In Zhejiang Province

The study of urban thermal environment has been appealed along with the urbanization procedure, while the thermal environment has a great relationship with the change of the impervious surface. For the sake of quality improvement of the urban thermal environment, it is important to study the temporal-spatial evolutions of the impervious surface and its effect on the urban thermal environment.Taking Zhejiang Province as the study area, the impervious surface information was extracted using the proper rules and thresholds derived from SEE5which is a tool of decision tree algorithm based on maximal entropy. Using landscape pattern analysis software, the impervious surface of Zhejiang province is analyzed in terms of the multiple scale space pattern metrics, in order to find its temporal-spatial varying trend. The distributions of the thermal status have been identified according to both the MODIS surface temperature data and the retrieved one. Finally, the relationship between the landscape metrics of impervious surface and the land surface temperature/the temperature zones was studied respectively by correlation analysis to indicate the effect of the landscape to the thermal environment.The main conclusions include:(1) The landscape metrics PD, PLAND, and LPI display the increasing trends between20years, while CONTAG and SHDI show non-linear patterns and opposite to each other. It implies that the impervious surface of Zhejiang Province have expanded in the temporal dimension, and concentrated in the spatial dimension. The urbanization of Zhejiang province is characterized as aggregation based on the dispersive centers.(2) The land surface temperature shows an increasing trend in500m resolution. The patches’area have been increased in high, sub-high, and medium temperature zones, and decreased in sub-medium and low temperature zones. The change is the most evident for the high temperature zones. The thermal fields have been gathered. With the inflation of the city, land surface temperature decreased along the direction from the city center to the outskirts.(3) Except for the CONTAG and the SHDI, all the landscape metrics have the relationships with the land surface temperature. LPI shows the maximal positive correlation with the temperature, then the AI and the PLAND. The PD has the weak negative correlation with the temperature. The relationship between the landscape metrics and temperature zones implies that the PD shows an inverse "U" along the temperature rating. There is a positive correlation between the temperature rating and the AI, LPI and PLAND of the impervious surface level. The CONTAG and the SHDI of the landscape level can’t reflect the relationship to the temperature rating.The above conclusions indicate that the larger area, the higher aggregation, and the more mono-type of the impervious surface will cause high land surface temperature and temperature rating. Thus, to avoid the worsening of the urban thermal status, it is suggested to develop more green lands and water bodies among the impervious surfaces, and reduce the aggregation of them.