A Comprehensive Dynamic Threshold Algorithm for Daytime Sea Fog Retrieval in the Chinese Adjacent Seas

【摘要】：正A comprehensive dynamic threshold algorithm for daytime sea fog retrieval is especially developed to distinguish sea fogs from marine boundary stratus based on Moderate Resolution Imaging Spectroradiometer (MODIS) data and sea surface temperature(SST).Sea fogs and marine boundary stratus(fog/stratus) are detected utilizing MODIS bands (0.62-12.27um) by already-existed methods at first.To overcome the resemblance in fog/stratus radiative spectrum,the discrepancies in temperature and humidity vertical structures between sea fogs and stratus are analyzed from soundings.The differences between SST and the brightness temperature from satellites are quite robust statistically between sea fogs and stratus,and thus the dynamic threshold are developed combining MODIS and climatologically monthly mean SST in the Yellow,Bohai and the Northern East China Seas.The retrieved sea fog areas are basically consistent with ground-based observations in two sea fog events in which both sea fogs and stratus exist.The distribution of the retrieved sea fog frequency in June from 2006-2010 including 120 images is compared with that from long term ICOADS data that involve ship-based fog observations. The retrieved higher fog frequency(15%) appearing in the Western Yellow Sea is compatible with the observations,while the two data sets are not in good agreement very likely due to the higher frequency of the occurrence of middle/high clouds over the sea fog areas in the Northern East China Sea.