REMOTE SENSING IMAGE-BASED ANALYSIS OF THE RELATIONSHIP BETWEEN 
URBAN HEAT ISLAND AND VEGETATION FRACTION 
Liqin Cao, Pingxiang Li, Liangpei Zhang, Tao Chen 
State Key Laboratory of information Engineering in Surveying, Mapping and Remote Sensing(LIESMARS), Wuhan 
University, 129 Luoyu Road, Wuhan, 430079 ,China- 
Caoliqin0823@126.com 
Commission VII, ICWG-VII-IV 
KEY WORDS: Urban heat island, vegetation fraction, the relationship 
ABSTRACT: 
As the relationship between land surface temperature (LST) and Normalized Difference Vegetation Index (NDVI) can not be able to 
effectively apply after NDVI reached saturation! 1]. In this study, the vegetation fraction, which derived from Dimidiate Pixel Model, 
as the indicator of vegetation abundance has been introduced to analyze remote sensing of the change of urban heat islands (UHIs). 
Landsat TM and ETM+ images of Wuhan from 1988 to 2002 were selected to retrieve the brightness temperatures and vegetation 
fraction. Results show that, from 1988 to 2002, the intensity of UHI was increased and the average vegetation fraction of the whole 
region was decreased. The urban ratio index (URI) of the study area was increased from 0.153 to 0.170 and the average vegetation 
fraction decreased from 58.41% to 50.45%. Our analysis showed that the UHI effect has become more prominent in areas of rapid 
changes as its vegetation fraction decreasing in the past decade. The brightness temperature had strong correlation with vegetation 
fraction, and the coefficient of determination value (R A 2) was 0.867, 0.843, 0.841, 0.843 of 1988, 1991, 1996 and 2002. 
1. INTRODUCTION 
Urban heat island (UHI) has long been a concern for more than 
40 years. UHI studies have traditionally been conducted for 
isolated locations and with in situ measurements of air 
temperatures. The advent of satellite remote sensing technology 
has made it possible to study UHI both remotely and on 
continental or global scale. Studies on the UHI phenomenon 
using satellite derived land surface temperature (LST) 
measurements have been conducted using various remote 
sending data such as NOAA AVHRR with 1.1km spatial 
resolutions[2~7], Landsat Thermatic Mapper (TM) and 
Enhanced Themtic Mapper Plus (ETM+) thermal infrared (TIR) 
data with 120m and 60m spatial resolutions, respectively, and 
so on. Researches on LST show that the partition of sensible 
and latent heat fluxes and thus surface radiant temperature 
response is a function of varying surface soil water content and 
vegetation cover. A higher level of latent heat exchange was 
found with more vegetated areas, while sensible heat exchange 
was more favored by sparsely vegetated such as urban areas. 
This finding encourages more and more research focusing on 
the relationship between LST and vegetation abundance[8~l 1]. 
Remote sensing of UHI has traditionally used the NDVI as the 
indicator of vegetation abundance to estimate the 
LST-vegetation relationship! 1]. However, LST-NDVI feature 
space will not be able to effectively apply when NDVI reached 
saturation. Vegetation fraction is an important index to scale 
the status of the vegetation of the region, and frequently used in 
monitoring vegetation status and the exchange of energy. In 
this study, using a Landsat TM and ETM+ imagery of the city 
of Wuhan, our purpose is to investigate the impact of the 
vegetation fraction changes on the intensity of the UHI effect in 
the region. Specific objectives of this research are: (1) to 
derived brightness temperature from Landsat TM/ETM+ 
thermal band for the period 1988-2002; (2) to estimate 
vegetation fraction for different times; (3) to investigate the 
change of brightness temperature and vegetation fraction in the 
city of Wuhan for 14 years; and (4) to quantitatively and 
quantitatively study the relationship between the intensity of 
UHI and vegetation fraction and how it has changed over time. 
2. DATA AND METHODS 
2.1 Study Area 
The City of Wuhan, located in Hubei Province, has been 
chosen as the area of study. The city is located on a flat plain, 
located between 113°41'E~115°05'E and 29°50'N ~31°22'N, 
with the area of 8467.6km2. The study areas include the center 
urban of the city and three suburbs (Caidian, Hannan and 
Jiangxia)(Figl). Huangpi and Xinzhou are excluded because of 
limitations of data. Detecting the relationship between UHI 
development and vegetation fraction is significant to 
understand, control, and plan the city's future development. 
Figure 1. the false image of the study area 
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