Labzovskii L D, van Zadelhoff G J, Tilstra L G, de Kloe J, Donovan D P, Stoffelen A
R&D Satellite and Observations Group, Royal Netherlands Meteorological Institute (KNMI), De Bilt, The Netherlands.
Sci Rep. 2023 Oct 16;13(1):17552. doi: 10.1038/s41598-023-44525-5.
Global ultraviolet (UV) surface reflectivity climatologies are all composed from daylight passive remote sensing observations of reflected UV light, generally integrated over a distribution of attainable reflection directions. We discovered the sensitivity of Aeolus lidar surface returns (LSR) to surface characteristics, providing the first evidence that active remote sensing can be effectively used for retrieving unidirectional UV surface reflectivity on global scales. LSR reproduces surface reflectivity monthly changes in Sahara, which are visible in the Lambertian Equivalent Reflectivity (LER) climatologies from TROPOMI and GOME-2. Very high correlations (r > 0.90) between gridded LSR and the LER climatologies are reported at global and regional scales for 36 different regions. Three clear land cover gradients are discerned from Aeolus LSR signal: (1) water/land, (2) vegetation/arid areas and (3) no snow/snow. The strongest LSR signal was retrieved over snow, while over vegetation, we found moderate negative agreement (r < - 0.60) between LSR and vegetation index proxy. Overall, the success of the first active remote sensing method for retrieving unidirectional UV surface reflectivity using Aeolus is demonstrated. Our approach can be effectively used to detect unresolved land and, especially, snow cover changes in high latitudes because, unlike passive instruments, Aeolus also provided nighttime observations.
全球紫外线（UV）表面反射率气候学均由对反射紫外线的日光被动遥感观测数据构成，通常是对一系列可获取的反射方向进行积分。我们发现了风神激光雷达表面回波（LSR）对表面特征的敏感性，这首次证明了主动遥感可有效用于在全球尺度上反演单向紫外线表面反射率。LSR再现了撒哈拉沙漠表面反射率的月度变化，这在TROPOMI和GOME - 2的朗伯等效反射率（LER）气候学数据中可见。在全球和区域尺度上，针对36个不同区域，网格化的LSR与LER气候学数据之间的相关性非常高（r > 0.90）。从风神激光雷达信号中可辨别出三个明显的土地覆盖梯度：（1）水/陆地，（2）植被/干旱地区，以及（3）无雪/有雪。在雪面上反演得到的LSR信号最强，而在植被覆盖区域，我们发现LSR与植被指数代理之间存在中等程度的负相关性（r < - 0.60）。总体而言，展示了利用风神卫星首次采用主动遥感方法反演单向紫外线表面反射率的成功。我们的方法可有效用于探测高纬度地区未解决的陆地，尤其是积雪覆盖变化，因为与被动仪器不同，风神卫星还提供夜间观测数据。
