Estimation of the Seawater Lidar Ratio by MODIS: Spatial-Temporal Characteristics and Ecological Significance.

The lidar ratio of seawater is an essential quantity related to both lidar retrieval and water constituent. However, few studies discuss its spatial-temporal characteristics and ecological significance, which limits its applications in lidar remote sensing and marine science. This paper investigates the spatial-temporal characteristics and ecological significance of the lidar ratio of seawater using satellite passive remote sensing, which is validated by in situ measurements. Spatially, nearshore lidar ratio values are higher than offshore, mainly owing to the high concentration of colored dissolved organic matter in nearshore water. Temporally, the lidar ratio in each hemisphere exhibits lower values in summer than in winter due to the annual boom-bust cycle of phytoplankton. Furthermore, the variability patterns of the lidar ratio are nearly consistent with those of the chlorophyll-to-carbon ratio, implying the high ecological significance of phytoplankton physiology. These findings will provide the foundation for the application of lidar ratio in marine science and lidar remote sensing.