西印度洋峡湾海区蒸发波导对电磁波传播影响研究

Study on the Influence of Evaporation Duct on Electromagnetic Wave Propagation in the Bay Area of West Indian Ocean

针对当前西印度洋峡湾海区蒸发波导对电磁波传播影响研究不足的现状,分析目前基于蒸发波导模型和电波传播模型相结合的综合分析方法在该热点海域使用的可行性,作者利用PJ蒸发波导模型和抛物方程模型开展研究。首先,归纳了PJ模型和抛物方程模型的基本思想和流程;然后,利用在西印度洋峡湾海区采集的气象水文、导航雷达探测距离等数据分析了模型预测结果与实测值的偏差。分析结果表明:实际距离与预测距离偏差在±25%以内的发生概率为91.3%,满足实际工作需要。不同时间段内模型的预测效果各不相同,06:00:00—12:00:00UTC对应的距离偏差均值最大,12:00:00—18:00:00UTC对应的距离偏差标准差最大。距离偏差与各类气象水文要素有显著的依赖关系,其中,距离偏差与气海温差的相关性最强。最后,通过使用经浮标数据检验的全球再分析资料数据集CFSRv2获得了西印度洋峡湾海区陷获频率时空分布结果。实验结果表明:在西印度洋峡湾内蒸发波导较易陷获电磁波,从而形成电磁波的超视距传输现象;而在也门和阿曼交界海域以及索科特拉岛附近水域蒸发波导全天的陷获能力较弱,出现超视距传播需要满足较高电磁波频率的条件。

According to insufficient research on the effect of evaporation duct on the propagation of electromagnetic wave in the bay area of West Indian Ocean,PJ evaporation duct model and parabolic equation method were used to investigate the feasibility of forecasting methods based on meteorological and hydrological data in the area.Firstly,the main idea and basic flow of the two models were summed up.The applicability of the two models in the bay area of West Indian Ocean was studied by using hydrometeorological data and range results of a navigation radar measured in the experiments during a certain month.The conclusion showed that the predicted range values were approximately equal to the measured ones.The probability of the difference（≤ 25%） was 91.3%.In addition,the prediction effect of the model was not the same in different time periods.Specifically,the average value of the percentage of distance deviation corresponding to the time period（06：00：00—12：00：00UTC） was the biggest,and the variance of the percentage of distance deviation corresponding to the time period（12：00：00—18：00：00UTC） was the biggest.Moreover,the deviation of the distance had a significant dependence on all kinds of meteorological and hydrological factors,among which ASTD（air sea temperature difference） had the strongest correlation.Finally,the spatial and temporal variability of minimum trapping frequency in these areas were also obtained using PJ model and reanalysis data（CFSRv2 which was tested using buoy data）.The results showed that microwave can be trapped easily in some regions of bay area and OTH phenomenon happened all the time.However,there were also some regions near Yemen,Oman and Socotra Island,where microwave cannot be trapped easily.In order to get OTH phenomenon in these regions,the higher frequency microwave was necessary.