中文摘要：

用MODTRAN模拟计算了全国34个地点的逐月和全年平均大气模式在940 nm波段的水汽透过率,并拟合出每种大气模式水汽透过率与水汽量经验关系式中的参数a、b。结果表明,参数a、b值与模式的整层大气可降水量有较好的相关性,并建立了a-W、b-W的经验关系式,且该关系式与海拔高度H（地面气压p0）有关。最后分析了a、b值的变化对地基消光反演水汽量精度的影响。

英文摘要：

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.