Studies On EOS/MODIS Data Processing And An Application On Monitoring Fog/Low Stratus By Daylight

MODIS data based on the file format of HDF has been applied in many fields and the Extraction MODIS Level 1B is a premise of application. Matlab provides a serious of APIs, which can be used in manipulation of HDF files, and it is convenient to deal with the data, especially for the scientific research staff, because of its calculating method by matrix. After studying the MODIS 1B file format, Matlab was used to extract data from MODIS 1B file, including reflectance/radiance calibration, solar zenith angle rectification, geographical interpolation and so on. And a flowchart of extracting MODIS Level 1B data was given for the purpose of development MODIS Level 2 products.A series of scientific data from previous experiments were analyzed and it can be draw the conclusion that in most experiment the diameter of fog droplet peek value is between 3 to 7 μ m,coincided to the medium - infrared. The fog droplet microcosmic character determined its radiative transfer property and influenced spectrum characters on satellite imagery. All these can be reflected on different sensors on satellite. The cloud, fog and land-surface features in VIS and IR were get based on the each spectral profiles and histograms analysis. Especially on medium-IR, the sunlight reflectance of fog is larger than the cloud's owned bigger diameter peek value. Furthermore, the sunlight reflectance of cloud and fog on medium-IR is not only related to the particle size distribution but also to the reflectance on VIS band. Accordingly, FDI(fog detection index) was proposed to help monitor fog. A flowchart of monitoring fog with the multi-spectral synthesis method was given and two examples were detected. The result showed that CSI was about 70%, FAR was about 10% and MDR was about 23%.