Spatial Pattern Changes Of The Impervious Surface And The Thermal Environment In Fuzhou City

Rapid urbanization results in the land-use change from natural surface into impervious surface constituted by such as asphalt and cement,which may lead to the change of thermal properties,therefore,the urban heat island(UHI)is becoming increasingly significant coupled with population growth and industrial production.Nowadays,thermal environment is becoming the core indicator affecting the quality of urban living.This study takes Fuzhou city as an example and 8 Landsat images from 1989 to 2013 as data sources.Firstly it disclosed the evolving characters of annual and seasonal spatio-temporal patterns of land surface temperature and impervious surface,and then computed the landscape indexes to illustrate the relationship between impervious surface area,landscape indexes and land surface temperature.The results are listed as following:(1)The spatial and temporal distribution characteristic of UHI effect is significantly obvious.The average land surface temperature increases from 27.07 ? in 1989 to 34.98 ? in 2013.UHI spatial aggregation effect is evident and the temperature in city center is higher than that in the suburban.The areas of the low,sub-low and medium temperature zones are gradually changing into sub-medium,sub-high and high temperature zones.The area of "high temperature zone" expands 4.77%and the direction of its extension is consistent with that of the urban expansion.The area of "high temperature zone" in Cangshan District increases 34.26%.The area ratio of "High temperature zone" accounts least in summer season(for example,it is 23.04%in 2002 and 26.87%in 2013)in summer,while it increases to the highest ratio in winter season.Now the UHI effect is most obvious in summer and worst in fall,but as the area ratio with extreme high temperature or high temperature zone has risen 7.87%and 8.23%respectively in fall and winter,so the UHI effect is more significantly enhanced in fall or winter season than that in summer.(2)The change characteristic of impervious surface is obvious.Impervious surface area increases 1.68 times in 24 years from 67.34 km2 to 180.32 km2,.and the average impervious surface coverage increases 8.10%.Coverage changes of different counties differ significantly.The average coverage of Gulou,Cangshan and Jinan Distrct increases year by year,and Cangshan increases most rapidly.The coverage of Taijiang Distrct dicreases 7.63%and the value of Mawei which is covered with woodland rises a lesser extent.(3)The relationship of impervious surface coverage and land surface temperature is significantly correlated.When the coverage of impervious land increases 0.1,the normalized temperature can increase 0.64.The landscape metrics named Aggregation Index and Percentage of Landscape Index have high relationships with the temperature,and its relevance is higher when the coverage is between 30%?05%or 50%-70%(up to 0.951).In summer,the correlation of indexes and normalized surface temperature is best and winter is weakest(up to 0.837).And it is showed the highest correlation with AI in 2002 and AI and PLAND in 2013 among all seasons.With the development of urbanization,correlation between indexes and temperature increase significantly in both fall and winter,thus UHI effect becomes more and more intense.