The thermal infrared radiance properties of dust aerosol over ocean

摘要

Asian dust storms, which can long-range transport to ocean, often occur during spring. The present of Asian dust aerosols over ocean makes some difficult for other studies, such as cloud detection, and also provide some advantages for ocean, such as adding nutrition to the ocean by dry or wet deposition. Therefore, it is important to study the dust aerosol and retrieve the properties of dust from satellite observations using mainly the thermal infrared radiance. In this paper, the thermal infrared radiance properties of dust aerosol over ocean are analyzed from MODIS and MTSAT2 observations and Streamer model simulations. By analyzing some line samples and a series of dust aerosol region, it shows that the dust aerosol brightness temperature at 12μm (BT_(12)) is always greater than BT_(11) and BT_(8.5), and BT_(8.5) is general greater than BT_(11). The different between brightness temperature at 11μm and 12μm wavelengths (BTD_(11-12)) increases with the dust intensity. Also, the BTD_(11-12) becomes positive when the atmospheric relative humidity is greater than 70%. The BTD_(11-12) increases gradually with the surface temperature while the effect of dust layer temperature on BTD_(11-12) is not evident. Those are caused by the transmission of the dust aerosol, which is different at the two thermal infrared channels. During daytime, dust infrared brightness temperature at mid-infrared bands should reduce those computed from the reflected solar radiance by dust. In general, BT_(3.7) is greater than BT_(11) for dust aerosol. Those results are helpful to monitor or retrieve dust aerosol physical properties over ocean from satellite.