THE VALIDATION OF AEROSOL OPTICAL THICKNESS RETRIED BY BAND 
CORRELATION METOD FROM MODIS IMAGE DATA 
Y. Kawata , H. Fukui and K. Takemata 
Earth and Social Information Core, Dept. of Computer Science, Kanazawa Institute of Technology, Japan - 
kawata@infor.kanazawa-it.ac.jp 
KEY WORDS: Remote Sensing, Atmosphere, Retrieval, Modeling, Algorithm, Surface 
ABSTRACT: 
We retrieved the aerosol optical thickness t, over Japan from several data sets of Terra/ASTER and Landsat-7/ETM- using the 
empirical band correlation method. This band correlation method for aerosol retrieval was originally proposed for MODIS data 
analysis by Kaufman et al.(1977)". The empirical band correlation of surface reflectance for certain land categories in Japan between 
the visible and infrared bands were computed using several data sets of Terra/MODIS in 2002 and 2003, together with the observed 
sky radiometer data. The results of retrieved aerosol optical thickness v, were validated with the simultaneous sky observation data 
at our study site. We found a good agreement between the retrieved and observed values. 
1. INTRODUCTION ratios for a land category between the visible reflectance and 
middle IR reflectance as follows: 
In the atmospheric correction of the remotely sensed earth 
image data we need the information on the aerosol optical Ta Ihr sen (vegetation) (1) 
parameters, such as the optical thickness t, , Ángstróm foy C, (urban) (2) 
exponent a, and the size distribution model. Since the sky fo Ip; C. (vegetation) (3) 
observation time is not always synchronized with the time of T io ns (urban) (4) 
satellite passing over, the method for retrieving the aerosol 
optical parameters from the satellite image data itself is highly where r,, r,, and r,, are the reflectance values in the band 
desirable. The band correlation method is supposed to be useful 7(central wavelength:\=2.16jim), band 1(A=0.645 um) and 
for retrieving the aerosol optical parameters from satellite data band 3(A=0.469 pm) of Terra/MODIS. They obtained the 
   
    
    
   
     
    
    
    
  
itself. In the band correlation method the empirical surface 
reflectance ratios for certain land categories between the visible 
and infrared bands are critically important. 
2. BAND REFLECTANCE RATIOS 
Kaufman et al.(1977)" found that there existed empirical band 
reflectance ratios, C, =0.50, C, =0.25 for vegetation, C, =0.69, 
and C,=0.42 for urban from the analysis of the TM and 
airborne measurement data in USA. In this study, we compute 
these reflectance ratios in Japan using the simultaneous sky 
measurement data and several image data sets of Terra/MODIS 
over Japan (May 06, 2002, April 07, April 16, May 09, and 
June 03 in 2003). First of all we classified the MODIS image 
Interna 
  
data inf 
sea, an 
band re 
snow, € 
The cl 
values 
obtaine 
atmosp 
thickne 
effects 
reflecta 
molecu 
found 1 
urban a 
as follo 
We sh 
between 
vegetati 
in band 
For giv 
distribu 
using L 
at the tc 
of the s 
given b 
example 
-(b), res 
We retri 
ÀA=0.661 
using tl 
section