Observed ocean surface albedo from a fixed offshore platform

The ocean surface albedo (OSA) is an important parameter in numerical ocean models and air‒sea heat flux calculations. Radiation observations were conducted to study the OSA in the northern South China Sea using a fixed offshore tower-based platform. The platform was located at 21.44° N, 111.39° E, with an average water depth of approximately 16 m. It consisted of a main tower and two auxiliary towers. The auxiliary towers were approximately 6 m from the main tower and their lower edges were approximately 6 m from the mean sea surface. A four-component net radiometer (CNR4) was installed on the lower edge of the southeast auxiliary tower through a 2-m long boom to simultaneously measure the upward and downward broadband solar radiation having spectral bands between 305 and 2800 nm. A bottom-mounted Nortek acoustic Doppler current profiler was used to measure surface waves. Other ancillary meteorological instruments were used to measure meteorological parameters, including wind speed and water vapor pressure. The observation period lasted from September 2017 to December 2018. The measured broadband radiation was collected in 30-min segments. To obtain an accurate and reliable radiation dataset, three specific types of data were removed from the dataset: (1) local afternoon data; (2) data with solar altitude angles

海洋表面反照率（Ocean Surface Albedo, OSA）是数值海洋模式与海气热通量计算中的关键参数。为探究南海北部的海洋表面反照率特性，研究团队依托固定式近海塔基观测平台开展辐射观测实验。该平台坐落于北纬21.44°、东经111.39°海域，平均水深约16米，由1座主塔与2座辅塔组成。辅塔与主塔间距约6米，其下缘距平均海面高度约6米。研究人员在东南侧辅塔的下缘通过2米长的悬臂杆安装了一台四分量净辐射计（four-component net radiometer, CNR4），可同步测量305~2800 nm光谱波段内的上行与下行宽带太阳辐射。此外，研究团队搭载了诺泰克（Nortek）声学多普勒海流剖面仪（acoustic Doppler current profiler）以观测表层海浪，并通过其他辅助气象仪器测量风速、水汽压等气象参数。本次观测周期为2017年9月至2018年12月，所获取的宽带辐射数据以30分钟为单位进行分段存储。为得到准确可靠的辐射数据集，研究人员从原始数据中剔除了三类特定数据：(1) 当日午后时段数据；(2) 太阳高度角相关数据。