Soil Moisture Mapping
Definition
Soil moisture mapping estimates the amount of water held in the soil profile, typically in the top few centimeters (surface) and sometimes deeper using models. Data come from in‑situ probes, microwave radiometers (e.g., L‑band) that sense dielectric properties, radar backscatter, thermal inertia, and land‑surface models that assimilate observations. Spatial resolution ranges from kilometers (passive microwave) to tens of meters (radar), with trade‑offs between coverage and detail.
Application
Agriculture adjusts irrigation schedules and predicts yield stress. Hydrologists improve runoff forecasts and flood warning by initializing catchment wetness. Wildfire agencies assess fuel moisture. Civil engineers manage earthworks and landslide risk. Ecologists study drought impacts on habitat and phenology.
FAQ
How do passive and active microwave approaches differ for moisture retrievals?
Passive sensors measure natural emission and provide direct but coarse estimates with good temporal stability. Active radar infers moisture from backscatter changes influenced by roughness and vegetation, offering finer detail but requiring careful calibration.
What is the value of data assimilation for sub‑surface moisture?
Assimilation blends sparse observations with a water‑balance model to estimate deeper layers and to maintain physical consistency, improving forecasts of runoff and evapotranspiration.
How do vegetation and surface roughness bias moisture retrievals?
Canopy attenuates signals and roughness increases backscatter, both mimicking moisture changes. Ancillary vegetation indices and roughness measurements help correct these effects.
When are citizen science probes worth integrating?
When professionally calibrated and geolocated, distributed probes fill gaps between satellites. Quality control and bias correction are essential before merging with official networks.