利用气象要素估算海洋大气近地层光学湍流

基于近地层相似理论以及极端层结下对该理论的修正,建立了海洋大气近地层光学湍流估算模型,并进行了数值分析。结果表明:当气温与海温相差较大时,温度起伏对光学湍流贡献最大;当气温与海温相差较小时,海面湿度越小,光学湍流越强;在较低湿度条件下,尤其在红外窗区,湿度扰动对光学湍流贡献起支配作用。当气温小于海温时,光学湍流先随海面风速增大而增强,后随风速增大而减弱;当气温大于海温时,光学湍流总体上是伴随海面风速增大而减弱。当气温小于海温或与海温接近时,与可见光和近红外波段相比,红外窗区光学湍流显著偏强;当气温远大于海温时,两波段光学湍流接近。在中性和近中性层结下,大气折射率结构参量C2n依赖于垂直高度的负幂指数接近-2/3,伴随海面大气层结稳定度或不稳定度增强,C2n依赖于垂直高度的负幂指数的绝对值分别逐渐减小或增大,并分别趋近于稳定极限下的0或不稳定极限下的-4/3。

Estimation of the Optical Turbulence in the Marine Atmospheric Surface Layer Based on Meteorological Data

A model used to estimate the optical turbulence in the marine atmospheric surface layer is developed based on the similarity theory and some modifications of the theory under the extremely stable and unstable conditions,and some numerical analyses are done.It is found that the temperature fluctuation dominates the contributions to the optical turbulence when the temperature difference between the air and the sea surface is large.As the temperature difference becomes smaller,the moisture fluctuation contribution becomes dominative,especially in the infrared windows,with the lower air moisture,and the lower the air moisture,the stronger the optical turbulence.Accompanying the strengthening of the surface wind,the optical turbulence first becomes stronger with the weaker surface wind,then weaker with the stronger surface wind when the air is cooler than the sea surface,but generally becomes weaker with the air being warmer than the sea.The optical turbulence is stronger in the infrared window than that in the visible and near-infrared band when the air is cooler or slightly warmer than the sea,but they are comparable when the air is much warmer than the sea.Under the neutral and near-neutral conditions,the dependence of the vertical profile of the structure parameter of the air refractive index,C2n,on the vertical height obeys the-2/3 power law.As the surface stability becomes more stable(unstable),the absolute value of the negative power of the profile becomes smaller(bigger),and approaches to 0(-4/3).