The Soil Moisture Active Passive (SMAP) "Soil Moisture 36 km (L2, Passive, Night, Dual Channel Algorithm)" layer displays surface soil moisture in cm³/cm³ posted on a 36 km EASE-Grid 2.0 derived from the Dual Channel Algorithm (DCA), one of four optional soil moisture algorithms, for 6:00 p.m. ascending (Night) half-orbit passes of the SMAP radiometer. The SMAP radiometer measures natural thermal emission emanating from the soil surface. The variation in the intensity of this radiation depends on the dielectric properties and temperature of the target medium, which for the near surface soil layer is a function of the amount of moisture present. In the DCA, both the vertically and horizontally polarized brightness temperatures are used to solve for soil moisture and vegetation optical depth.

The SMAP spacecraft carries two instruments, a radar (active) and a radiometer (passive), that together make global measurements of land surface soil moisture and freeze/thaw state. It is useful for monitoring and predicting natural hazards such as floods and droughts, understanding the linkages between Earth’s water, energy and carbon cycles, and reducing uncertainties in predicting weather and climate.

References: SMAP L2 Radiometer Half-Orbit 36 km EASE-Grid Soil Moisture

Data field: soil_moisture_option3