NASA's Soil Moisture Active and Passive mission (SMAP) will provide global maps of soil moisture content and surface freeze/thaw state. Global measurements of these variables are critical for terrestrial water and carbon cycle applications. The SMAP observatory consists of two multipolarization L-band sensors, a radar and radiometer, that share a deployable-mesh reflector antenna. The combined observations from the two sensors will allow accurate estimation of soil moisture at hydrometeorological (10 km) and hydroclimatological (40 km) spatial scales. The wide-swath (1000 km) measurements will allow global mapping of soil moisture and its freeze/thaw state with 2-3 days revisit. Freeze/thaw in boreal latitudes will be mapped using the radar at 3 km resolution with 1-2 days revisit.
SMAP radar measurements have a spatial resolution of 1-3 km over the outer 70% of the swath. The high resolution of the radar is critical for accurate determination of freeze/thaw state in the heterogeneous landscapes of the boreal forest region north of 45N latitude. The 40-km soil moisture product is derived from the radiometer measurements. The active radar and passive radiometer measurements are combined to generate an intermediate resolution 10-km product that optimizes the resolution and accuracy attributes of the radar and radiometer. Although SMAP directly observes only surface soil moisture (in the top 5 cm of the soil column), many users require knowledge of root zone soil moisture (~top 1 m of the soil column), which is not directly measured by SMAP. The root zone Level 4 product will be obtained by merging SMAP observations with estimates from a land surface model in a soil moisture data assimilation system.
Results/Conclusions
The synergy of active and passive observations enables measurements of soil moisture and freeze/thaw state with unprecedented resolution, sensitivity, area coverage and revisit. These measurements will be used to enhance understanding of processes that link the water, energy and carbon cycles, and to extend the capabilities of weather and climate prediction models. SMAP science measurements will enable applications in decision support and policy-relevant systems including drought and flood guidance, agricultural productivity estimation, weather forecasting, climate predictions, disease risk assessment and national security This poster will present information about this upcoming NASA mission and will provide descriptions of several key projects, applications and techniques that will use the information when the sensor is launched.
