3km SMAP/CYGNSS Soil Moisture

3km SMAP/CYGNSS soil moisture is a downscaled Soil Moisture Active Passive (SMAP) soil moisture product. We downscaled 9km SMAP enhanced brightness temperatures by merging them with L-band Cyclone Global Navigation Satellite System (CYGNSS) reflectivity data, using a modified version of the SMAP active-passive brightness temperature algorithm. We then calculated 3km SMAP/CYGNSS soil moisture using the resulting 3km SMAP/CYGNSS brightness temperatures and the SMAP single channel vertically-polarized soil moisture algorithm (SCA-V). To remedy the sparse daily coverage of CYGNSS data at 3km spatial resolution, we used spatially interpolated CYGNSS data to downscale SMAP soil moisture. 3km interpolated SMAP/CYGNSS soil moisture has a repeat period of ~2-3 days.3km分辨率SMAP/CYGNSS土壤湿度是一款经降尺度处理的土壤湿度主动被动（Soil Moisture Active Passive，SMAP）土壤湿度产品。本研究将9km分辨率的SMAP增强型亮温数据与L波段气旋全球导航卫星系统（Cyclone Global Navigation Satellite System，CYGNSS）反射率数据进行融合，并采用改进后的SMAP主动-被动亮温算法完成降尺度操作。随后，利用生成的3km分辨率SMAP/CYGNSS亮温数据，结合SMAP单通道垂直极化土壤湿度算法（SCA-V），计算得到3km SMAP/CYGNSS土壤湿度。针对3km空间分辨率下CYGNSS数据每日覆盖范围稀疏的问题，本研究采用经空间插值处理的CYGNSS数据对SMAP土壤湿度进行降尺度。经空间插值后的3km SMAP/CYGNSS土壤湿度产品的重访周期约为2至3天。