File : D4.11
Author : Tuula Aalto (FMI)
Natural CH4 emissions are an important component of the global CH4 budget, and the largest source of natural emissions is from wetlands. A novel Data Assimilation System (DAS) for improving CH4 flux estimates from wetlands was developed, which complements estimation of natural CH4 emissions by process modelling and inversions. The CH4-DAS was built on the wetland CH4 emission model, HIMMELI, and the atmospheric transport model, TM5. The CH4-DAS utilises atmospheric concentration observations and measurements of ecosystem fluxes at two ICOS wetland sites (Siikaneva at Hyytiälä area and Lompolojänkkä at Pallas area, Finland). CH4-DAS optimises the concentration priors from TM5 and flux priors from HIMMELI against the measurements. The sensitivity of the agreement between the model and measurements to parameters in the process model was analysed with CH4-DAS/HIMMELI. Optimisation of the process model parameters enabled estimation of the relative magnitudes of production and oxidation fluxes contributing to the net methane fluxes from wetlands. Results from CH4-DAS are presented for the two sites as well as future directions for running a regional simulation with the system.
