Since LNG vapors are just CH4/C2H6/air gas mixtures of low concentration, you can use any gas convection models. Cold mist will generate visible fog around, so look for fog evolution models for different wind velocities.
The methods for prediction of the dispersion of LNG are under intensive development and it is difficult to recommend any specific model at this stage. For the detailed information please consult the recent PhD thesis. The application of Computational Fluid Dynamics (CFD) is discussed in the PhD Thesis: “Liquified Natural Gas (LNG) vapor dispersion modeling with computational Fluid dynamics codes” by Ruifeng Qi. The text is available at:
The general review of available techniques is also presented in the dissertation by Walter Chukwunonso Ikealumba: “Mathematical Modelling of LNG Dispersion Under Various Conditions”, the text can be found at:
The limitations of existing models are discussed extensively in the above thesis.
Personally, I believe that the modeling of LNG vapors is much more complicated that simulation of traditional air pollutants, however, some of the experience, particularly with the meteorological data will be useful in modeling of this emerging air pollutant.
the reason is due to boiling of the gas out to the atmosphere, in a real geometry of city in 2D, I am trying to identify a model that can deal with different weather conditions.