SMAP L4 Global 3-hourly 9 km EASE-Grid Surface and Root Zone Soil Moisture Geophysical Data, Version 5

SMAP Level-4 (L4) surface and root zone soil moisture data are provided in three products: * SMAP L4 Global 3-hourly 9 km EASE-Grid Surface and Root Zone Soil Moisture Geophysical Data (SPL4SMGP, DOI: 10.5067/9LNYIYOBNBR5) * SMAP L4 Global 3-hourly 9 km EASE-Grid Surface and Root Zone Soil Moisture Analysis Update (SPL4SMAU, DOI: 10.5067/0D8JT6S27BS9) * SMAP L4 Global 9 km EASE-Grid Surface and Root Zone Soil Moisture Land Model Constants (SPL4SMLM, DOI: 10.5067/5C36BVQZW28K). For each product, SMAP L-band brightness temperature data from descending and ascending half-orbit satellite passes (approximately 6:00 a.m. and 6:00 p.m. local solar time, respectively) are assimilated into a land surface model that is gridded using an Earth-fixed, global cylindrical 9 km Equal-Area Scalable Earth Grid, Version 2.0 (EASE-Grid 2.0) projection.SMAP四级（L4）表层与根区土壤湿度数据集共包含三类产品： * SMAP L4全球3小时分辨率9公里等面积可缩放地球网格（Equal-Area Scalable Earth Grid，EASE-Grid）表层与根区土壤湿度地球物理数据集（SPL4SMGP，DOI：10.5067/9LNYIYOBNBR5） * SMAP L4全球3小时分辨率9公里EASE-Grid表层与根区土壤湿度分析更新数据集（SPL4SMAU，DOI：10.5067/0D8JT6S27BS9） * SMAP L4全球9公里EASE-Grid表层与根区土壤湿度陆面模型常数数据集（SPL4SMLM，DOI：10.5067/5C36BVQZW28K）。 针对每一类产品，将获取自降轨与升轨半轨卫星过境（分别对应当地太阳时约上午6:00与下午6:00）的SMAP L波段亮温数据，同化至采用地球固定型全球圆柱9公里等面积可缩放地球网格2.0版（EASE-Grid 2.0）投影进行网格化的陆面模型中。