中文摘要：

大气修正折射指数（M）廓线是描述大气折射环境的重要参数,也是评估电波传播的关键因子。为了提高稳定特别是强稳定层结条件下模型预测M廓线的效果,引入三种非线性无量纲相似函数BH91、CB05、SHEBA07对原始的Babin_V25模型进行了改进,并利用铁塔平台实测气象水文数据对改进后的模型预测效果进行了评估,同时将其与改进前的Babin_V25模型以及Local_HYQ92模型的效果进行比较。结果表明：引入非线性相似函数能明显改进模型预测M廓线的效果,尤其是最新发展的SHEBA07,改进后的Babin_SHEBA07模型能在稳定层结条件下预测M值、0~5 m及5~40 m内的M梯度均方根误差分别减少64.5%、16.6%和60.4%,但这种方法对蒸发波导高度的预测效果改进不明显;而基于局地相似理论的Local_HYQ92模型则能使稳定层结条件下M值、0~5 m内、5~40 m内的M梯度以及蒸发波导高度d的预测均方根误差分别减少76.7%、40.2%、83.7%和58.0%。考虑到在电磁波传播特性的评估中,M梯度比蒸发波导高度和M值本身更为重要,最终推荐在强稳定层结条件下选用Local_HYQ92模型和Babin_SHEBA07模型。

英文摘要：

Modified refractivity（M） profile is an important parameter in describing the atmospheric refraction environment and a key factor in the electromagnetic wave propagation evaluation.To improve the model-derived M profiles in stable,especially very stable,conditions,three nonlinear similarity functions,namely,BH91,CB05,and SHEBA07,were introduced to improve the original Babin_V25 model,and the hydrometeorological observations from the iron tower platform were utilized to evaluate the effects of the modified models,which were finally compared with the original Babin_V25 model and Local_HYQ92 model.Results are as follows.Introducing nonlinear similarity functions,especially the newly developed SHEBA07 functions,can significantly improve the model-derived M profile,and the predicted root-mean-square M difference and M slope difference for both 0~5 m and 5~40 m in stable conditions can be reduced by 64.5%,16.6%,and 60.4% respectively when the modified Babin_SHEBA07 model is applied.Unfortunately,however,this method cannot improve the prediction of the evaporation duct height.In contrast,the Local_HYQ92 model based on the theory of Local Similarity can manage to reduce the predicted root-mean-square M difference,M slope difference for both 0~5m and 5~40 m,and evaporation duct height difference by 76.7%,40.2%,83.7%,and 58.0%,respectively.Finally,a new recommendation is made to adopt Local_HYQ92 and Babin_SHEBA07 in very stable conditions in view of the more important role played by the M slope in determining electromagnetic propagation as compared to duct height and absolute M values.