Model Infrastructure

Within AIRSPACE, an infrastructure consisting of two different model systems will be established in order to use the data streams of the individual instruments for modelling the greenhouse gas fluxes.

1. Regional inverse modelling

2. Chemistry-climate modelling with regional refinement

Both models ideally complement each other, because they have been built for different purposes and with different foci. This allows also the assessment of the uncertainties by comparing the results of both models. STILT-TM3, operated by MPG-BGC, is a coupled regional Eulerian-Lagrangian model, which has been primarily developed to reduce transport errors in continental-scale top-down estimates of terrestrial greenhouse gas fluxes. It will be used for backward trajectory computations originating at the measurement sites to assess the source-receptor relationships, which are the basis for inverse flux estimates and source attributions. Using the WRF (Weather Research and Forecasting) model instead of  ECMWF analyses will allow to operate this model in forecast mode for flight planning but also results in higher spatial resolution for a better interpretation of the atmospheric transport.

MECO(n) (“MESSy-fied ECHAM and COSMO models nested n-times”), operated by DLR, is the global chemistry-climate ECHAM/MESSy Atmospheric Chemistry model (EMAC) with a regional, multiple zooming capability based on the COSMO model of the German Weather Service (DWD). The on-line coupling of the different model instances allows for a frequent exchange of boundary conditions between the coarser (global or regional) and the next finer (regional) resolved model instances thus guaranteeing for a consistency between all relevant spatial scales. These unique strengths of MECO(n) will be exploited for AIRSPACE

• to hind-cast the measurement campaigns on the regional scale, however consistently embedded into the global scale

• to assess the role of the different methane sources within and outside the campaign region

• to assess the chemical state of the atmosphere determining the photochemical lifetime of methane on both, the regional and the global scale, and

• to simulate the isotopic composition (D, ¹³C) of methane on both, the global and the regional scale.

Furthermore, a recently developed diagnostic technique to represent “emission (and age) classes” of methane will be used to complement the inversion based on WRF-STILT.

In brief, WRF-STILT will be used to directly invert the observations from the measurement campaigns (assuming a known methane sink) with the best estimate of atmospheric transport, and MECO(n) will be used to assess the corresponding aspects of atmospheric chemistry (sink processes).