The Soil Moisture Active Passive (SMAP) “Percent Frozen Area (L4, 9 km Grid Cell Coverage, Model Value-Added)” layer displays an environmental constraint defined as the percent frozen area within each 9-km grid cell, as defined by daily surface temperature inputs from the Goddard Earth Observing System Model, Version 5 (GEOS-5) land model. Percent frozen area, combined with environmental constraints on temperature and moisture, facilitates improved algorithm and product accuracy over heterogeneous land cover areas, and product outputs that are more consistent with the mean sampling footprint of most tower CO₂ flux measurement sites.

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 L4 Global Daily 9 km Carbon Net Ecosystem Exchange

Data field: frozen_area