(Georgia Institute of Technology, 2017-05-07)
Lin, Liao-Fan; Bras, Rafael L.
This document presents the data sample size of the SMAP L2 Version 4 soil moisture retrievals for each month during 2016 and the percentages of the soil moisture data within some quality control limits defined by NASA. The soil moisture retrievals of each 36-km grid cell are associated by NASA to a surface condition and retrieval quality flag. Each half orbit was obtained from https://nsidc.org/data/SPL2SMP/versions/4. There are 11 surface conditions defined in the SMAP data: static water, radar-derived water, coastal proximity, urban area, precipitation, snow, permanent ice, frozen ground from SMAP radiometer-derived freeze/thaw state, frozen ground from GMAO TSURF model, mountainous terrain, and dense vegetation. For each surface
condition, a lower threshold T1 and a higher threshold T2 are defined. Only data with all surface conditions under the T1 threshold are flagged as high quality. In this document, we use three variables (i.e.,soil_moisture, surface_flag, and retrieval_qual_flag) from each data file to illustrate the distribution and quality of the data.