201 
SPATIAL DISTRIBUTION AND SEASONAL CHANGES OF URBAN AND SUBURBAN 
SURFACE RADIATION BUDGET IN BEIJING 
J. Zhou, Y. H. Chen*, J. Li 
State Key Laboratory of Earth Surface Processes and Resource Ecology, College of Resources Science & Technology, 
Beijing Normal University, Beijing 100875, China - (zhouji, cyh, lijing)@ires.cn 
KEY WORDS: Albedo, Land Surface Temperature, Radiation Budget, Land Cover, Remote Sensing, Urban 
ABSTRACT: 
Under the context of rapid urbanization, radiation budget is crucial to analyse the adverse climate effects in urban environments, 
especially for mega-cities. Selected Beijing city and surrounding regions as the study area, this paper investigated the spatial 
distribution patterns and temporal variations of radiation budget based on integration of remote sensing images and ancillary data. 
Landsat-5 Thematic Mapper (TM) images and meteorological data acquired in the summer and winter were used to calculate land 
surface parameters and the net radiation flux. Validation with in situ measurement shows that the calculation of net radiation yielded 
high accuracy. In order to understand the spatial patterns of radiation budgets, the net radiation flux, albedo, and land surface 
temperature were analysed in terms of variations among different land cover types. Results indicate that the city can be characterized 
as a “basin” of net radiation in the summer, while a “plateau” in the winter. The albedo and land surface temperature were two 
primary factors contributing to the spatial variations of net radiation, while the solar elevation angle controlled the seasonal 
variations of the absolute amount. 
1. INTRODUCTION 
Fast urbanization induces adverse climatic effects for urban 
environments and surrounding areas, even for local and macro 
scale regions. Radiation budget, which is also named as net 
radiation flux and defined as the difference between the 
incoming and outgoing radiation fluxes at the surface of earth 
(Bisht et al., 2005), plays as the dominant element of energy 
exchange between land surface and atmosphere. Because of 
intense human activities and complicated artificial landscapes, 
the radiation budget in urban environment is different from that 
of natural surfaces greatly. This has become one of the focuses 
of urban environment researches. 
With the advent of satellite remote sensing, especially the 
remote sensors with higher spatial resolution at thermal 
channels, e. g. Landsat TM/ETM+, Terra ASTER, some 
researchers have examined the applicability and feasibility of 
these images to investigate the radiation budget in the urban 
and suburban areas (Chrysoulakis, 2003; Frey et al., 2007; Rigo 
& Parlow, 2007). It has been confirmed that the integration of 
remote sensing images and ancillary data is an appropriate and 
helpful route to grasp the patterns of radiation budget in 
different urban areas and at different spatial and temporal scales. 
As the capital and second largest city in China, Beijing has 
been influenced by intense urban climate problems because of 
its mass population, traffics and the unique physical settings. 
This paper has two objectives: 1) Calculation the net radiation 
flux of the urban and suburban areas in Beijing; 2) Analysis the 
spatial distribution patterns and seasonal changes of radiation 
budget. The results will be useful for understanding the change 
rules of urbanization in the process of urban climate for such a 
mega-city. 
2. STUDY AREA AND DATA 
Beijing city and surrounding regions were selected as the study 
area (Fig.l). 
Figure 1. Map of the study area 
Two Landsat-5 Thematic Mapper (TM) images, acquired on 
July 4, 2004 and December 3, 2006, were utilized to examine 
the spatial distribution of radiation budget in summer and 
winter in the study area. Both images were geometric rectified 
with ENVI soft package based on a rectified ASTER VNIR 
image. Then the digital number (DN) of all bands was 
Corresponding author.