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European CH4 emissions from CTE-CH4 atmospheric inverse model

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European CH4 emissions from CTE-CH4 atmospheric inverse model

Authors
Aki Tsuruta (FMI)
Abstract

In this study, we examine European CH4 emissions using an atmospheric inverse model, CarbonTracker Europe-CH4 (CTE-CH4). The model assimilates global atmospheric CH4 observations with intense observation network in Europe (incl. ICOS stations) to derive flux scaling factors for anthropogenic and biospheric (wetland and soil sink) sources. The sensitivity of the estimated emissions are tested by using two different prior flux fields for anthropogenic and biospheric sources. For anthropogenic sources, EDGAR v4.2 FT2010 and EDGAR v4.3.2 is used; v4.2 FT2010 fields are only annual means, while v4.3.2 fields have monthly varying seasonal cycles for each source component. For the biospheric sources, estimates from an ecosystem model (LPX-Bern DYPTOP) and those from previous GCP-CH4 are used. The GCP-CH4 biospheric fields are from the bottom-up estimates, and has no interannual variations. In addition, sensitivity to the assimilated observations were tested by running two inversions; 1) uses high-precision observations from ground-based stations, and 2) uses dry air total column-averaged CH4 mole fractions, retrieval from GOSAT TANSO-FTS. The estimated emission showed clear seasonal cycle in the northern and eastern European CH4 emissions, mainly driven by biospheric sources, while central European CH4 emission showed little differences during winter and summer. The inversion using GOSAT retrievals showed larger CH4 emissions in northern and eastern Europe compared to those using ground-based stations, while that of central Europe was lower. We evaluate those results by comparing with process-based models and inversion-independent observations.

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