Spatial-temporal Characteristics of Urban Heat Island in Typical Cities of Anhui Province Based on MODIS

Anhui Province is a place with great economic development and potential that lies in the hinterland of the Yangtze River Delta. The topography and climate of Anhui Province present obvious variousness, which can be divided into three natural regions: North China plain, Jianghuai hills and mountain areas of south Anhui. Anhui Province covers an area of 139600 km². The population of Anhui Province reaches 68.62 million by the end of 2010. Since the 1990s, great changes have happened in Anhui Province, e.g., the tremendous growth of urban sprawl, population, vehicles and economy. In recent years, great increase in urban heat island (UHI) intensity also takes place in the areas with the most rapid urbanization due to fast economic growth and the increasing desire of people for an urban lifestyle. Hefei, the capital of Anhui Province, locating between the Yangtze River and the Huaihe River with hilly terrain, the non-rural area population and urban built-up area of which reaches 1800000 and 326 km² in 2010, respectively. Wuhu, the economic center of southern Anhui, locating to the south of the Yangtze River with mountainous terrain, the non-rural area population and urban built-up area of which are respectively 950000 and 135 km² in 2010. Fuyang, the economic center of northern Anhui, locating to the north of Huaihe River with a flat sub-layer, the non-rural area population and urban built-up area of which are 490000 and 76 km² in 2010, respectively. Land surface temperature (LST) retrieved from MODIS data is used to explore the characteristics of urban heat island (UHI) in Province during 2001 to 2010. Considering some factors (climate, geography and urbanization), three cities mentiened above are first selected to study the UHI. Moreover, diurnal and seasonal variations of LST in these cities are captured by MODIS with GIS technology. Finally, spatial-temporal characteristics of urban heat island are analyzed in representative cities of Anhui Province. The result shows that the heat island effect of Hefei is the most significant. The intensities of UHI in representaty cities of Anhui is stronger in the south area than in the north. Especially, diurnal and seasonal characteristics presented significantly. In recent 10 years, the UHI area and UHI intensity in representative cities maintain increasing tendency, while the extreme UHI intensity (more than 3 ℃) has a weaker enhancement in Hefei. Large bodies of water have a significant role in weakening the city heat island effect in daytime, while have no impacts on UHI effect in nighttime, even becoming high value center of LST. LST and NDVI show significant negative correlation in summer, so it is very important for improving vegetation coverage of the city to reduce land surface temperature and weaken the effects of UHI.