RESEARCH ON TEMPORAL AND SPATIAL VARIATION OF HEAT ISLAND EFFECT IN XI'AN, CHINA

This paper takes Xi'an, which is a western city in China, experiencing the rapid urbanization, as the research object. It uses 2000 Landsat7 ETM+, 2010 Landsat5 TM and 2016 Landsat8 OLI images as data sources to inverse and normalize surface temperature. Thermal field intensity index (HFI) and urban heat island proportion index (UHPI) were introduced to quantitatively assess the temporal and spatial variation of heat island in Xi'an. Research results demonstrate: (1) From 2000 to 2016, the average temperature in urban areas increased from 32.34 degrees C in 2006 to 42.45 degrees C in 2016, with an increase of 10.11 degrees C in 16 years. (2) From 2000 to 2016, the urban heat island area continuously increased, from 40.59 km(2) in 2000 to 81.52 km(2) in 2016, with an increase of about 100.87%. UHPI increased from 0.036 in 2000 to 0.078 in 2016, which indicates the scientific rationality of the index to a certain extent. (3) According to the distribution law, the heat island scope and urban expansion reflect strong time-space consistency. In the 16 years, the distribution pattern of thermal environment changed from central urban area distribution mode to built-up area distribution mode. (4) From the perspective of the distribution in administrative region, heat island effect was mainly distributed in the old areas such as Lianhu District and Xincheng District in 2000. Due to urban expansion, the phenomenon of hollow heat island appeared in 2010. In 2016, heat island effect was distributed in all six areas.