Parametrization of total atmospheric absorbing transmittances by water vapor at 940 nm in China

The water vapor transmittances in the 940 nm band are computed using MODTRAN for 34 sites in China.Parameters a and b for all the atmospheric models in the empirical water vapor transmittance function are fitted.It is found that the values of a and b is the function of atmospheric water vapor amount.The empirical functions are established for the relationships between the values of a and b and atmospheric model's perciptible water.Considering the parameter of the surface altitude H(or surface pressure p0),the empirical coefficients related to H are parameterized.Finally,the uncertainty in retrieved PWV caused by parameter a and b is analyzed.