Top-down constraints on global N2O emissions at optimal resolution: Application of a new dimension reduction technique

摘要: Abstract. We present top-down constraints on global monthly N2O emissions for 2011 from a multi-inversion approach and an ensemble of surface observations. The inversions employ the GEOS-Chem adjoint array aggregation strategies to test how well current observations can constrain spatial distribution emissions. include (1) a standard 4D-Var inversion at native model resolution (4° × 5°), (2) six continental three ocean regions, (3) a fast based a novel dimension reduction technique employing randomized singular value decomposition (SVD). optimized flux ranges 15.9 Tg N yr−1 (SVD-based inversion) 17.5–17.7 Tg N yr−1 (continental-scale, standard inversions), with former better capturing extratropical background measured during HIAPER Pole-to-Pole Observations (HIPPO) airborne campaigns. find that tropics provide a greater contribution than is predicted by prior bottom-up inventories, likely due underestimated agricultural oceanic infer overestimate natural soil in extratropics are seasonally biased northern midlatitudes. Here, fluxes exhibit a springtime peak consistent timing spring fertilizer manure application, thawing, elevated moisture. Finally, reveal a major emission underestimate US Corn Belt inventory used here. extensively impact initial conditions analysis recommend formally optimizing avoid biasing inferred fluxes. SVD-based provides a powerful framework deriving information observations: defining optimal solution content inversion, it lost when aggregating political or geographic while also providing more temporal inversion.