A new iterative retrieval method for ocean attenuation profiles measured by airborne lidar

Lidar remote sensing for ocean optical properties has been increasingly applied because of its ability to provide vertical structure information, which cannot be directly obtained by ocean color remote sensing. However, the application of this technology demands an inversion method to infer two quantities, i.e., attenuation and backscatter, from a single measurement. Here, a new iterative retrieval method is demonstrated to deduce the attenuation coefficient from ocean lidar return signals. One calculates the logarithmic backscatter-to-attenuation ratio $k$k by an iterative solution based on a bio-optical model. Procedural examples of lidar-processing results—from raw data to attenuation—are presented, and the inversion results are compared with in situ measurements. The correlation coefficient R between the lidar-retrieval and in situ measurements is 0.8, and the root mean square error (RMSE) is 0.032. We then map the vertical structure of the lidar-retrieved attenuation along airborne lidar flight tracks and discuss the influences of $k$k, the reference depth ${z_m}$zm, and the reference value ${\alpha _m}$αm. Consequently, the reference value has little influence on the results for high-optical-thickness water, and $k$k is the main error source in lidar return inversion. Primary results indicate that this method provides a more accurate $k$k and improves the inversion accuracy of the lidar attenuation coefficient.