Concerning various kinds of low visibility weather phenomena and based on the existing dichromatic atmospheric scattering model, a modified calculating method of dichromatic model is proposed, to range weather phenomenon via revising the atmospheric scattering direction, improving the calculating method of vector angles and adding humidity parameter information The improved algorithm model has higher stability, considering that the scatter light direction is not all consistent and pixels have three dimensional character in the RGB space Embedding the algorithm into the model and computing the corresponding eigenvalues, these weather phenomena can be recognized through the empirical thresholds By improving the calculating method and processing the seasonal data of Columbia University and two month data of Zhangye Observatory, it is shown that the improved method is excellent in identifying various kinds of low visibility weather phenomena, such as fog, haze, dust blowing, dust floating, and sand storm, whose total identification rates for the above two regions are 732% , 905%, respectively.