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THE IDENTIFICATION OF YELLOW SAND DUST ON SATELLITE-LEVEL DATA OVER EAST ASIA 
USING LONG-RANGE TRANSPORT MODELS AND POLARIZATION MEASUREMENTS 
T. Kusaka, T. Ema and N. Murata 
Kanazawa Institute of Technology 
7-1 Nonoichi-machi Ishikawa 921, Japan 
E-mail: kusaka@neptune.kanazawa-it.ac.jp 
Commission VII Working Group 5 
KEY WORDS: Yellow sand dust Long-range transport 
model Polarization ADEOS/POLDER 
ABSTRACT: 
The yellow sand dust (called "Kosa" in Japan) transported 
from the deserts in the northern part of China often covers 
over East Asia in spring. A method for identifying “Kosa 
clouds”, which consist of yellow sand dust particles, on 
ADEOS/POLDER data by using the polarization data 
acquired by the POLDER sensor and the long range 
transport simulation of yellow sand particles is described. 
As a result, it is shown from the results of the long range 
transport simulation that the high density Kosa cloud moves 
from the main land of China to the Sea of Japan. The thick 
cloud like the Kosa cloud is visible in the POLDER image 
taken on April 12, 1997. The polarization in regions that 
are regarded as the Kosa cloud in the POLDER image was 
examined. It was found that the Kosa cloud in the 
POLDER image consist of dust particles in the range from 
lpm to Sum. 
1. INTRODUCTION 
The yellow sand dust transported from the deserts in the 
northern part of China is regarded as the main source of 
atmospheric aerosols for East Asia in spring. The dust 
particles in the air have significant effects on retrieving the 
ocean color and the vegetation index from satellite-level 
data, because in the visible and near infrared channels, the 
radiance received by the satellite sensor significantly 
includes the skylight scattered diffusely by the yellow sand 
dust. The optical properties of yellow sand dust have been 
studied by means of Lidar observation from ground stations 
(Arao 1986, Kai 1988). However, it is as yet very difficult 
to extract “hazy Kosa clouds”, which consist of yellow sand 
dust particles, from the satellite-level data such as NOAA 
AVHRR and Japanese meteorological satellite (GMS). 
The objective of this study is to identify “Kosa clouds” on 
ADEOS/PODER images on the basis of the polarization 
measured from the POLDER sensor and the long range 
transport simulation of yellow sand dust. 
We can see thick Kosa clouds on satellite-level data such as 
GMS data, but in general the widely spread hazy Kosa 
clouds are invisible on the satellite image. On April 12 and 
13, 1997, the Kosa events were observed at meteorological 
stations at the side of the Sea of Japan. We have POLDER 
data over East Asia including the Sea of Japan acquired on 
April 12 and 13, 1997. It is however difficult to distinguish 
between clouds and “Kosa clouds” on the POLDER data. 
Therefore, we simulated the movement of yellow sand dust 
particles for East Asia by using the long-range transport 
model including dry and wet depositions to extract the 
regions where it looks like Kosa clouds from POLDER 
images. Then we identified “Kosa clouds” on POLDER 
images on assuming that the degree of polarization of 
“Kosa clouds” is different from that of normal clouds. 
2. ADEOS/POLDER DATA 
The POLDER sensor developed by CNES, France was 
carried on the ADEOS satellite launched by NASDA, 
Japan in 1996. Unfortunately, the ADEOS loss occurred in 
1997. However, the POLDER data sets during 8 months 
are now available. The POLDER sensor observes the 
polarized intensity at three channels (443, 670 and 865nm) 
as well as reflectances in visible and near infrared spectrum 
bands. The degree of linear polarization Lp (96) is defined 
by Stokes parameters I, Q, U as follows: 
Lp = 100*sqrt(Q” + U%) / I 1) 
, Where I is the total intensity, Q and U the excess in 
intensity of light transmitted by a polarizer. Since the values 
of I, Q and U are given in POLDER level 1 data (POLDER 
1997), we can easily compute the degree of polarization at 
every pixel of POLDER data. 
On April 12 and 13, 1997, the yellow sand dust was 
observed at meteorological stations at the side of the Sea of 
Japan. We have POLDER images over East Asia just taken 
on these days. Figs.] and 2 show the shaded images 
generated from the composite color images (Blue: 443nm, 
Green: 565nm, Red: 765nm) of POLDER data taken on 
April 12 and April 13, 1997, respectively. Comparing with 
Figs.1 and 2, we can see that the thick “Kosa”-like clouds 
move from the western part of Korea to the Sea of Japan, 
and that the Sea of Japan near Japan is covered with the 
thin “Kosa” like cloud. Fig.3 shows the profiles of 
polarization (%) versus the scattering angle at three 
Intemational Archives of Photogrammetry and Remote Sensing. Vol. XXXII, Part 7, Budapest, 1998 439