ERA-I数据在南海大气折射率环境中的应用评估

Evaluation on the application of atmospheric refractive index from ERA-I data over the South China Sea

海上大气折射率环境是影响电磁波传播、目标探测准确性的关键因素之一.文中利用南海的GPS探空数据评估了ERA-I(ERA-Interim)再分析数据计算的大气折射率,结果表明:3000 m以下修正大气折射率整体标准差为9.2 M单位,相对误差为1.4%;在分布上修正大气折射率误差在低层偏小,并且会发生小幅震荡,边界层顶以上偏大,这与大气层内水汽分布密切相关,相关系数为0.94.此外两种数据识别的波导参数中,波导高度拟合斜率接近1,最准确;波导厚度和强度斜率不到0.5,波导厚度偏厚,而强度偏小.说明ERA-I再分析数据是较为可靠的数据源,可用来研究海上大气折射环境特性.

Atmospheric refractive environment over the sea is one of key factors on estimation of electromagnetic wave propagation and target detection.Evaluation on atmospheric refractivity over the South China Sea from ERA-I reanalysis data was carried out using the Globle Position System(GPS)radiosonde data.The results show that the global standard deviation and relative error of the modified atmospheric refractive index bellow 3000 m heights is about 9.2 M units and 1.4%respectively.On altitude distribution,the modified atmospheric refractivity index is less estimated,displaying small-amplitude fluctuations in the lower atmospheric layer and larger estimated above the top heights of marine atmospheric boundary layer,which is closely related with the water vapor pressure distribution in the atmospheric layer and their correlation coefficient is 0.94.Moreover,for the duct parameters from ERA-I data,their duct heights are are consistent well with those from GPS radiosonde data,with their slope about 1 and their duct thicknesses are larger and duct strengths are weaker than those from the observed data,with each of their slope close to 0.5.The EAR-I reanalysis dataset over the sea is reliable and useful data source to study the marine atmospheric refractive environment.