JPL SMAP Level 3 CAP Sea Surface Salinity Standard Mapped Image 8-Day Running Mean V4.2 Validated Dataset

This is the PI-produced JPL SMAP-SSS V4.2 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. SMAP-SSS V4.2 is a complete reprocessing of the entire mission series following on from the reprocessing of the source L1B-TB data by the SMAP mission on 6/4/2018. Updates in v4.2 include: improvement in the brightness temperature (TB) calibration using an adjusted reflector emissivity, inclusion of a Sea Surface Temperature (SST) dependent flat surface emissivity model, use of updated land correction tables, and inclusion of averaged ice concentration ancillary data in the v4.2 product. 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制JPL SMAP-SSS V4.2 CAP，8日运行平均值，三级映射，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，最初是在Aquarius/SAC-D的背景下进行开发，现已扩展至SMAP。SMAP-SSS V4.2是对整个任务系列进行完整重处理的结果，继2018年6月4日SMAP任务对源L1B-TB数据进行重处理之后。v4.2版本中的更新包括：使用调整后的反射器发射率改进亮度温度（TB）校准，包含海面温度（SST）依赖的平坦表面发射率模型，使用更新的陆地校正表，以及在v4.2产品中包含平均冰浓度辅助数据。此三级产品的每日数据文件基于覆盖8日移动时间窗口的海面盐度平均值。相关文件变量包括：由SMAP得到的导出SSS及其不确定性以及风速数据，辅助冰浓度和HYCOM表面盐度数据。SMAP数据始于2015年4月1日，持续更新中，处理和可用性存在7日延迟。L3产品覆盖全球范围，以0.25度x0.25度的网格进行排列，空间分辨率约为60公里。SMAP卫星位于接近极地轨道，倾角为98度，高度为685公里。其上升节点时间为下午6点，为太阳同步轨道。SMAP的1000公里扫描宽度使得卫星大约在3天内实现全球覆盖，但具有精确的8日轨道重复周期。卫星搭载的高灵敏度L波段辐射计在1.41GHz频率下运行，并配备有L波段1.26GHz雷达传感器，提供互补的主动和被动传感能力。2015年7月7日SMAP散射仪的故障，迫使使用共定位风速来校正表面粗糙度，以实现表面盐度检索。