Technical Abstract: Soil moisture spatial variability patterns are identified using measurements across different scales and depths from 18 different experiments. The spatial variability patterns are well represented by negative exponential functions between the mean and the coefficient of variation of soil moisture. Rainfall and topography are the most important physical parameters to understand how surface soil moisture variability changes as soils dry. Soil parameters control the maximum relative variability. The soil moisture variability typically decreases as sampling scale increases, while the soil moisture variability increases as soil depth increases. These common soil moisture variability patterns can provide a feasible methodology to validate land surface models.