Estimation of the temporal and spatial distribution of the optically thin Asian dust from satellite image data

一般来说，在卫星图像上识别广泛分布在陆地表面的模糊沙尘云是非常困难的。在这项研究中，一个新的方法来估计的时间和空间分布的光学薄亚洲尘埃。（1）2000 - 2005年3 - 5月在日本金泽市地面站用多光谱偏振仪对天空辐射进行了偏振测量。在本研究中，（i）制作了从偏振仪测量的偏振数据库中检索偏振度的Web应用系统，（ii）从75 °、90 °、105和120度从太阳方向在主平面的开发。(2)A提出了一种利用ADEOSII/POLDER单通道数据同时估算亚洲沙尘光学特性和地面反射率的新算法。为了评估该算法，在地面站测得的偏振度进行了比较，从ADEOSII/POLDER数据估计在2003年5月3日。结果表明，在670 nm波段上估算的亚洲尘埃光学参数值是合理的。(3)In为了估算亚洲沙尘在东亚地区的时空密度分布，采用了沙尘粒子的长程输送模拟模式。确定了亚洲沙尘的释放区域和质量通量，使得从远程传输模拟中获得的亚洲沙尘浓度几乎等于在日本各地测量的SPM（悬浮颗粒物）浓度。

In general, it is very difficult to identify the widely spread hazy dust cloud in satellite images over the land surface. In this study, a new method for estimating the temporal and spatial distribution of the optically thin Asian dust was developed.(1)Polarization measurements of the sky radiation by the multi-spectral polarimeter have been carried out at the ground station in Kanazawa city, Japan from March to May in 2000 to 2005. In this study, (i) Web application system for retrieving degrees of polarization from the database of polarization measured properly by the polarimeter was made, and (ii) the method for estimating optical properties of Asian dust, such as the optical thickness, the number size distribution and the refractive index, and the ground reflectance from polarization data measured at angles of 75, 90, 105 and 120 degrees from the solar direction in the principal plane was developed.(2)A new algorithm for estimating optical properties of the hazy Asian dust and the ground reflectance simultaneously from ADEOSII/POLDER data over the land surface received at a single channel was developed. In order to evaluate the algorithm, degrees of polarization measured at the ground station are compared with those estimated from ADEOSII/POLDER data on May 3, 2003. As a result, it was found that the values of optical parameters of Asian dust estimated at the 670nm channel provide reasonable ones.(3)In order to estimate the temporal and spatial density distribution of Asian dust over East Asia, the long-range transport simulation model of dust particles was used. The released region and mass flux of Asian dust was determined such that the concentration of Asian dust obtained from the long-range transport simulation is almost equal to that of SPM (Suspended Particulate Matter) measured at various places in Japan.