The Thexmex-18 Dataset: Understanding the Soil and Vegetation Dynamics of Agricultural Fields in Central Mexico from L-Band SMAP Observations

The National Aeronautics and Space Administration (NASA) Soil Moisture Active Passive (SMAP) satellite was launched in January 2015. In order to validate the soil moisture retrieval algorithms that fully exploit the unique capabilities of SMAP, the algorithms need to be tested over different conditions worldwide. In response to this need, the Terrestrial Hydrology Experiment 2018 in Mexico (THExMEX-18) was conducted in a rainfed agricultural region of Huamantla, Tlaxcala, Mexico over a six-month growing season. During the experiment, soil moisture, crop measurements, and biomass samples were collected. The objective of THExMEX-18 was to create a soil moisture network over an agricultural area in Mexico, understand the spatial distribution of soil moisture, and compare the SMAP soil moisture retrievals with in-situ measurements. This work details the field data collection as well as data calibration and analysis. A first comparison between in-situ data and SMAP retrievals of soil moisture is presented. It is demonstrated that absolute soil moisture values can be retrieved by satellite observations. SMAP soil moisture estimates closely follow dry down and wetting events observed during the field experiment.