高反射率地区气溶胶光学厚度遥感反演:现状及展望

Aerosol Optical Thickness Retrieving Over Bright Surface:Progress and Prospect

气溶胶在地球大气辐射收支平衡和全球气候变化中扮演着重要的角色。利用卫星数据反演水体、浓密植被等暗背景上空的气溶胶光学厚度已经达到了较高的精度,而对于干旱、半干旱以及城市等高反射率地区,气溶胶光学厚度反演仍面临严峻挑战。高反射率地区气溶胶光学厚度反演的困难主要是地表反射率的确定精度较低;气溶胶的指示作用随着地表反射率的升高而降低。为精确反演高反射率地区的气溶胶光学厚度,国内外开展了大量的研究工作。本文介绍了对比算法、高反差地表法等几种主要的反演方法,介绍了这些方法的理论基础,指出了它们的优势与不足,并分析了高反射率地区气溶胶光学厚度反演的发展前景。

It is a great challenge to retrieve aerosol optical thickness over bright surface from remotely sensed data, because it is very difficult to estimate the reflectance of the complicated surface accurately, and the radiance is not sensitive to the aerosol change when the surface reflectance is high. To overcome the difficulties of aerosol optical thickness retrieving in the bright areas, many methods were provided. We introduced some significant methods： 1） contrast reduction algorithm. This method applied in a sequence of satellite images which contain a clear image; 2） high contrast surfaces algorithm. This method can retrieve aerosol optical thickness from two closely located, high contrast surfaces; 3） two or more sensors cooperation method, which can retrieve aerosol optical thickness together with surface reflectance; 4） methods which are based on surface reflectance database/model, which need to ascertain the surface reflectance accurately. We analyzed the advantages and disadvantages of each method. At last, we provided the prospect of the aerosol optical thickness deriving over bright surface. The construction of surface reflectance database and the development of the BRDF model make the surface reflectance more accurate, the increasing aerosol measuring stations advance our quantitative understanding of aerosol characteristics, and the design of many new satellite sensors which can derive the aerosol optical thickness becomes more perfect. All of the above factors can help aerosol optical thickness retrieving a lot.