珠江口溶解有机物的遥感动态监测

河口有色溶解有机物（colored dissolved organic matter,CDOM）的分布是各种物理-生物地球化学过程共同作用的结果。为实现河口高动态变化CDOM的监测,遥感是一种重要的手段。由珠江口四个不同季节的航次获得的实测数据,本文构建了一个遥感算法以反演CDOM在400 nm的吸收系数（a_CDOM （400））。该算法使用以波段反射率比值R_rs （667）/R_rs （443）和R_rs （748）/R_rs （412）为自变量。将构建的算法应用于2002-2014年的MODIS/Aqua数据,本文计算了珠江口不同季节的a_CDOM （400）气候态分布。CDOM的分布主要受珠江径流量和区域水下地形特征的影响。沿着垂直于水深梯度的断面,气候态a_CDOM （400）呈指数减少（y=ae^bx,b<0）,但不同季节差异很大。珠江口CDOM主要是河流淡水输运而来。其中,富里酸比例随盐度的增加而降低。基于构建的算法、CDOM保守混合方程和径流量,本文由MODIS/Aqua数据进一步估算了2002-2014年夏季和冬季珠江DOC的有效入海浓度和有效入海通量。珠江的有效入海浓度和有效入海通量都与流量存在正相关关系,且在夏季的相关性更明显,R2分别为0.698和0.9657。

The dynamic observation of dissolved organic matter in the Zhujiang (Pearl River) Estuary in China from space

The distributions of estuarine colored dissolved organic matter (CDOM) are the combined results of physicalbiogeochemical processes. Remote sensing is needed to monitor highly dynamically estuarine CDOM. Using in situ data from four seasonal cruises, an algorithm is developed to estimate CDOM absorption coefficient at 400 nm (a_CDOM(400)) in the Zhujiang (Pearl River) Estuary (ZJE). The algorithm uses band ratios of R_rs(667)/R_rs(443) and R_rs(748)/R_rs(412). By applying it to moderate resolution imaging spectroradiometer onboard Aqua satellite (MODIS/Aqua) data from 2002 to 2014, seasonal climatology a_CDOM(400) in the ZJE is calculated. CDOM distributions are majorly influenced by water discharge from the Zhujiang River and underwater topography. Along the section vertical to a water depth gradient, the seasonal a_CDOM(400) exponentially decreased (y=ae^bx, b<0), but with great differences among seasons. Riverine fresh water is the primary source of CDOM in the ZJE. Fulvic acid fraction decreases with increasing salinity. Using developed algorithms, conservative CDOM mixing equation, and river discharge, effective riverine end-member concentration and flux of dissolved organic carbon (DOC) in summer and winter from 2002 to 2014 are first estimated from the MODIS/Aqua data. Both effective riverine end-member DOC concentration and flux are positively related to the river discharge, significantly in summer with R² of 0.698 for concentration and 0.965 7 for flux.