Comparison of SMAP Retrieval Soil Moisture Level 2 Product with in Situ Measurements over Corn Fields in Central Mexico

Since 2018, the Terrestrial Hydrology Experiment in Mexico (THExMEX-18) is being part of SMAP algorithm validation through soil moisture (SM), crop measurements, and biomass samples that were collected over a rainfed agricultural region of Huamantla, Tlaxcala. As a second part of this experiment, THExMEX-19 was carried out in whole crop season from March to December 2019. In order to help to validate to SMAP algorithm applying NASA's protocols, both joint efforts of National Polytechnic Institute and Center for Remote Sensing of the University of Florida have obtained these results in 2018 and 2019. In-Situ soil moisture measurements are compared with the enhanced soil moisture SMAP level 2 passive observation (SMAP L2-SM-P and SMAP L2-SM-P-E) and soil moisture SMAP level 2 and Sentinel-1 passive observation (SMAP L2-SM-SP). SMAP mission meets the requirement of SM retrievals with an unbiased root-mean-square difference (ubRMSD) < 0.04 (m3 m-3) compared to in-situ measurements over agricultural fields. The L-band passive SM retrievals and in-situ measurements were evaluated in terms of four statistical metrics: root-mean-square difference (RMSD), bias, ubRMSD, and correlation coefficient (r).