The Soil Moisture Active Passive (SMAP) “Net Ecosystem CO2 Exchange (L4, 9 km Grid Cell Mean, Model Value-Added)” layer displays model-derived global gridded mean daily estimates of net ecosystem carbon (CO₂) exchange in grams of carbon uptake per meter squared per day (gC m^-2 day^-1) posted on a 9 km EASE-Grid 2.0. The net ecosystem exchange of CO₂ with the atmosphere is a fundamental measure of the balance between carbon uptake by vegetation gross primary production (GPP) and carbon losses through autotrophic (Ra) and heterotrophic (Rh) respiration. The sum of Ra and Rh defines the total ecosystem respiration rate (Rtot), which encompasses most of the annual terrestrial CO₂ efflux to the atmosphere.

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. The imagery resolution is 2 km and sensor resolution is 9 km. The temporal resolution is daily.

References: SMAP L4 Global Daily 9 km Carbon Net Ecosystem Exchange

Data field: nee_mean