Improving CLM5.0 Biomass and Carbon Exchange Across the Western United States Using a Data Assimilation System

Area of Science:

• Ecology
• Earth System Science
• Remote Sensing

Background:

• Western US natural lands are vital for carbon balance, water quality, and timber, but vulnerable to mortality.
• Complex terrain challenges carbon monitoring, creating a need for data assimilation systems.
• Integrating land surface models with satellite data offers improved ecosystem health assessment.

Purpose of the Study:

• To enhance carbon monitoring in the Western US using data assimilation.
• To adjust the Community Land Model (CLM5.0) with satellite-derived leaf area and biomass data.
• To investigate the impact of data assimilation on carbon fluxes and ecosystem processes.

Main Methods:

• Utilized the Data Assimilation Research Testbed (DART) to adjust the Community Land Model (CLM5.0).
• Incorporated remotely sensed observations of leaf area and above-ground biomass.
• Compared simulation results with a separate observation-constrained model (FLUXCOM).

Main Results:

• Adjusted simulation significantly reduced leaf area and above-ground biomass, lowering photosynthesis and respiration.
• Reduced carbon fluxes largely offset each other, projecting a weak carbon sink, contrary to FLUXCOM's strong uptake.
• Water limitation was identified as a key factor influencing the magnitude and spatial pattern of carbon uptake.

Conclusions:

• Improved carbon monitoring in the Western US requires data assimilation systems.
• Including water cycling observations (e.g., snow water equivalent, land surface temperature) is crucial for accurate carbon uptake patterns.
• Enhancing assimilation systems to adjust more state variables, particularly those related to water and soil carbon, is recommended.