Evaluation of NASA SMAP soil moisture data in wet and dry spells using in situ observations

Abstract. Ground-based measurements of soil moisture (SM) present accurate time series of this variable whereas the spatial disparity of SM is unknown. This knowledge gap can be filled using remote sensed datasets that provide high spatial resolution information of SM. This study evaluates remote sensed data from the NASA Soil Moisture Active Passive (SMAP) satellite. The data from SMAP were compared with the in situ observations collected by the International Soil Moisture Network. The evaluation results of remote sensed SM products were assessed in diverse climate divisions as well as different main land cover classes in the state of Kansas in both wet and dry spells through correlation analysis. The spatial analysis revealed the prominent impact of climate divisions and vegetation types on data. The results indicated that SMAP L4 SM retrievals are generally better when considering the impact of both climate and land cover in analyzing the data. Using both climate divisions and vegetation types suggest a more robust understanding of relationship between data sources specially in short dry and wet spells, which may play critical role for agriculture.