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气象卫星热红外通道能够探测到晴空区域内由大气水汽、沙尘气溶胶等物质含量分布不均所导致的微弱的纹理信息,通过追踪水汽和沙尘气溶胶纹理的移动可以反演出风场。然而这些信号很容易受地表温度变化的影响,需使用合适的算法来减弱地表温度干扰、提取微弱的示踪物信号。本文结合分裂窗差值理论,对使用分裂窗差值算法提取晴空区微弱示踪物信号进行数值模拟分析,并应用于晴空区风场的实例反演。数值模拟图像的结果显示,分裂窗差值算法可以削弱地表对示踪物信号的影响,突出水汽和沙尘气溶胶的分布特征,验证了分裂窗差值法的可行性与优越性。实例分析也表明,使用分裂窗差值图能够反演出单通道云图难以得到的晴空区低层风场,且反演结果与NCEP风场资料比较一致。
The meteorological satellite thermal infrared channel can detect weak texture information caused by the uneven distribution of atmospheric moisture and dust aerosols in the clear sky, and can trace the wind field by tracking the movement of water vapor and dust aerosol texture. However, these signals are susceptible to changes in surface temperature. Appropriate algorithms are used to mitigate surface temperature disturbances and to extract weak tracer signals. Based on the theory of split-window difference, this paper analyzes the weak tracer signal in the clear-air zone by using split-window algorithm, and applies it to the inversion of the wind field in the clear sky. The results of numerical simulation show that the algorithm of split window difference can weaken the influence of surface on the tracer signal, highlight the distribution characteristics of water vapor and dust aerosol, and verify the feasibility and superiority of split window difference method. The case study also shows that using the split-window difference map can invert the low-level wind field in the clear-air region which is not easily obtainable by the single-channel cloud image, and the inversion results are in good agreement with the NCEP wind field data.