利用MODIS资料定量判识沙尘暴方法研究

A Study on Quantitative Identification of Sand and Dust Storm Using MODIS Data

为了利用MODIS资料对沙尘暴的范围和强度进行定量判识，应用多时次MODIS多波段资料，在对沙尘暴、云、雪和沙漠光谱特征进行较为细致分析的基础上，寻找出能区分沙尘、云和地表的波段，构建了2个定量判别沙尘暴范围和强度的沙尘指数，并利用沙尘指数对2002—2005年多次MODIS沙尘暴的范围和强度进行判识。研究结果表明：1）沙尘在反射光谱段的光谱特征为反射率随着波长的增加而增大，与土壤光谱特征相近；大粒径沙尘反射率增长速率大于小粒径沙尘。2）小粒径沙尘具有较典型的气溶胶特征，对0.46μm蓝光波段敏感，对1．6和2．1μm短红外波段不敏感。3）大粒径沙尘不具有气溶胶特性，对蓝光波段不敏感，对短波红外敏感。4）3．7μm和8．5μm是对沙尘敏感波段，2波段的差可以作为判别沙尘的指标，并在一定程度上反映沙尘强度。5）设计的2个沙尘指数对监测沙尘十分有效，且方法简单，适于业务应用。

In order to detect the scope and intensity of sand and dust storm quantificationally by using MODIS data, the spectrum characteristics of sand and dust storm, cloud and snow were analyzed in detail using several MODIS data, bands that can distinguish sand and dust from cloud and surface were detected, two indices for determining the scope and intensity of sand and dust storm were found out and tested in several cases. Our study shows ： 1 ） The spectrum characteristic of sand and dust in solar wavelengths is that the reflectance increases with the wavelength, this is similar to soil, and the reflectance of large size dusts increases faster than small size dusts. 2） Small size dusts show typical characteristic of aerosol, which are sensitive to blue band of 0.46 μm and insensitive to short - wave infrared bands of 1.6 and 2.1 μm. 3） Large size dusts do not have aerosol characteristic, they are insensitive to blue band and sensitive to short - wave infrared bands. 4） Dusts are sensitive to bands of 3.7 μm and 8.5 μm , and the difference of the two bands can be used to identify sands and dusts and reflect the intensity to certain extent. 5 ） The two indices are very effective to monitor sands and dusts, and the method is simple and easy for operational use.