Novel Earth Observation Products to Characterise Wetland Extent and Methane Dynamics: the ESA ALANIS-Methane Project
Hayman, Garry1; Clark, Douglas1; Blyth, Eleanor1; Bartsch, Annett2; Christoph, Paulik2; Stefan, Schlaffer2; Julia, Reschke2; Catherine, Prigent3; Aires, Filipe4; Buchwitz, Michael5; Schneising, Oliver5; Burrows, John5; O'Connor, Fiona6; Gedney, Nicola6
1Centre for Ecology and Hydrology, UNITED KINGDOM; 2Technical University of Vienna, AUSTRIA; 3CNRS Observatoire de Paris, FRANCE; 4Estellus, FRANCE; 5University of Bremen, GERMANY; 6Met Office Hadley Centre, UNITED KINGDOM

The role of wetlands in the global methane cycle is the subject of much current interest [1,2]. Wetlands are generally accepted as being the largest, but least well quantified, single source of methane (CH4), with emission estimates ranging from 100-231 Tg yr-1 [3,4]. Since the late 1970s, there have been significant inter-annual variations in the growth rate of atmospheric methane, which has been linked inter alia to the variability in wetland CH4 emissions [5,6]. Despite much progress, the recent wetland model intercomparison [7] still indicates significant differences between models and uncertainties in the associated methane emissions.

Although the emissions of methane from the wetlands and lakes of the boreal region are smaller than those from tropical wetlands, the size and remoteness of the boreal region pose a significant challenge to the quantification of both terrestrial ecosystem processes and their feedbacks to regional and global climate. In recent years, Earth Observation (EO) data have demonstrated the potential to become a major tool for characterizing the main processes and estimating key variables governing the land-atmosphere interface. To aid the realisation of this potential, the European Space Agency (ESA) initiated the Atmosphere-LANd Interactions Study (ALANIS), in collaboration with the Integrated Land Ecosystem-Atmosphere Processes Study (iLEAPS). One of the three ALANIS themes investigated wetland dynamics and methane emissions (denoted ALANIS methane,

The ALANIS methane project had a focus on the boreal Eurasia region. There were two main goals: (1) to produce a suite of relevant datasets derived from Earth Observation (EO) and (2) to use these (and other) EO products to evaluate and improve the Joint UK Land Environment Simulator (JULES,, a state-of-the-art land surface model. The project has produced a number of new or extended EO-based products for boreal Eurasia, which are highly relevant to the surface characterization of wetlands (see Figure 1) and their emissions of methane:

  • wetland/inundation dynamics for the period July 2007 to June 2008 using ASCAT (MetOp-A) and SSM/I (DMSP) data, supplemented with vegetation indices derived from AVHRR data (CNRS/Estellus);
  • wetland/inundation dynamics at higher spatial resolution from ASAR (Envisat) wide swath data for the spring/summer months of 2007 and 2008 (TU Wien);
  • surface state (frozen, unfrozen and melting) from ASCAT (MetOp-A) data for the years 2007-2010 (TU Wien); and
  • atmospheric CH4 columns derived from SCIAMACHY data (Envisat) for the years 2003-2009 (Bremen).

    The products are available via the project website ( and click on Datasets).

    Figure 1: Inundation extent as derived for the boreal domain for July 2007 from the regional inundation product (Panel a) and the classification of open water bodies and peatlands from the higher resolution product for the Ob and Lena rivers (Panel b). Panel c shows a comparison of the two products for various locations within the Ob and Lena rivers.

    The wetland emission scheme in JULES had previously been evaluated at specific locations where measurements had been made. This was the first time that the wetland scheme had been evaluated over a larger spatial domain. The EO products listed above were used to evaluate the performance of the JULES land surface model in two configurations: (a) offline [8,9] and (b) as the land surface component of the Hadley Centre’s HadGEM2 coupled climate-chemistry model [10].

    The outputs from JULES in its offline configuration were compared with the wetland inundation and surface state EO products. The SCIAMACHY column methane dataset was used to discriminate between different spatial configurations of the global emissions from wetlands and other methane sources. Figure 2 presents comparisons of the zonal mean atmospheric methane mixing ratios derived from the Sciamachy (v2.3) product and the corrected HadGEM2-ES output for 2003-2007 (sampled at common space and time points) from runs using the JULES wetland emission estimates with (a) the modelled and (b) EO-derived wetland fractions. These evaluations have identified a number of aspects of the hydrology and biogeochemistry of the wetland modelling in JULES that need to be improved.

    Figure 2: Zonal mean atmospheric methane mixing ratios as derived from the common time and space data between January 2003 and December 2007 in the Sciamachy (v2.3) product (regridded to the model spatial domain, black) and the corrected HadGEM2-ES model output (using HALOE-ACE TOMCAT) (red) for runs using the JULES wetland emission estimates with the modelled (xfzav, panel a) and EO-derived (xfzaw, panel b) wetland fractions.

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