JPL SMAP Level 3 CAP Sea Surface Salinity Standard Mapped Image 8-Day Running Mean V4.3 Validated Dataset

This is the PI-produced JPL SMAP-SSS V4.3 CAP, 8-day running mean, level 3 mapped, sea surface salinity (SSS) product from the NASA Soil Moisture Active Passive (SMAP) observatory. It is based on the Combined Active-Passive (CAP) retrieval algorithm developed at JPL originally in the context of Aquarius/SAC-D and now extended to SMAP. Improvements with V4.3 include: 1) New residual TB calibration which removes the ascending/descending bias issue observed for version 4.2; 2) Slightly modified criteria for aggregation from L2B to L3 based on TB for V-pol minus TB for H-pol. Daily data files for this L3 product are based on SSS averages spanning an 8-day moving time window. Associated file variables include: derived SSS with associated uncertainties and wind speed data from SMAP, ancillary ice concentration and HYCOM surface salinity data. SMAP data begins on April 1, 2015 and is ongoing, with a 7-day latency in processing and availability. L3 products are global in extent and gridded at 0.25degree x 0.25degree with an approximate spatial resolution of 60km. The SMAP satellite is in a near-polar orbit at an inclination of 98 degrees and an altitude of 685 km. It has an ascending node time of 6 pm and is sun-synchronous. With its 1000km swath, SMAP achieves global coverage in approximately 3 days, but has an exact orbit repeat cycle of 8 days. On board instruments include a highly sensitive L-band radiometer operating at 1.41GHz and an L-band 1.26GHz radar sensor providing complementary active and passive sensing capabilities. Malfunction of the SMAP scatterometer on 7 July, 2015, has necessitated the use of collocated wind speed for the surface roughness correction required for the surface salinity retrieval.

此为美国宇航局土壤湿度主动被动（SMAP）观测站生产的PI生成JPL SMAP-SSS V4.3 CAP产品，8日滑动平均值，为三级映射的海面盐度（SSS）产品。该产品基于喷气推进实验室（JPL）开发的综合主动被动（CAP）检索算法，最初在Aquarius/SAC-D项目背景下研发，现扩展至SMAP项目。V4.3版本中的改进包括：1）引入新的残余热通量校正，消除了版本4.2中观察到的上升/下降偏差问题；2）基于垂直极化热通量减去水平极化热通量的V-pol，对L2B至L3的聚合标准进行略微调整。该三级产品的每日数据文件基于跨越8日移动时间窗口的SSS平均值。相关文件变量包括：导出的SSS及其相关不确定性以及来自SMAP的风速数据，辅助冰浓度和HYCOM表面盐度数据。SMAP数据自2015年4月1日开始，持续进行中，处理和可用性存在7天的延迟。三级产品覆盖全球范围，以0.25度x0.25度的网格进行划分，空间分辨率约为60公里。SMAP卫星运行在近极地轨道，倾角为98度，高度为685公里，升交点时间为下午6点，且为太阳同步轨道。其1000公里的扫描宽度使得SMAP在大约3天内实现全球覆盖，但确切的轨道重复周期为8天。卫星搭载的高灵敏度L波段辐射计工作在1.41GHz频率，以及L波段1.26GHz雷达传感器，提供互补的主动和被动探测能力。2015年7月7日SMAP散射仪的故障，迫使在表面粗糙度校正过程中使用同位风速，以实现表面盐度检索。