A detection algorithm for Asian dust aerosol over China Seas based on MODIS observations

Abstract

Asian dust storms, which often occur on spring, can long range transport and pass through the China Seas. During this process, it makes some impact on marine ecology and region climate. In this paper, the optical and thermal properties of Asian dust aerosols are firstly presented from the satellite MODIS observations. By comparing strong dust, weak dust, clear water and clouds, the reflectances of dust aerosols over ocean at the visible 0.47μm 0.86μm, and the near-infrared 1.64μm have some significant features, it satisfies R0.47<R1.64<R0.86 for strong dust aerosol over ocean, the weak dust aerosol meets R1.64<R0.47<R0.86, even R1.64<R0.86<R0.47, and the dust reflectance may be from 0.1 to 0.3. At the thermal atmospheric windows bands 8.5, 11 and 12μm, for cloud and clear water region, the brightness temperature at 12μm is highest and the temperature at 11μm is close to 12μm. However, for dust aerosols, the brightness temperature at 12μm is much greater than those at 8.5μm and 11μm. The brightness temperature difference between 8.5μm and 11μm is small and the lower is the difference, the stronger is the dust aerosol. Based on those visible and thermal characteristics, a detection algorithm for dust aerosols over ocean is designed and is conducted for some cases. It can identify the strong and the weak dust regions well and it is nice to study the dust properties deeply.