Danish Ministry of Environment

<p>1. The interim regional scalability plans (RSP) are the next step on the roadmap to upscale freshwater ecosystem restoration after the optimisation strategies (MERLIN Deliverable 2.1). They offer visions for upscaling restoration across wider areas by 2050.<br>\n2. A template has been designed for collecting input using the manual "Scaling up - From vision to Large-Scale Change. A Management Framework for Practitioners" (Management Systems International 2016).<br>\n3. Seventeen case studies have prepared their interim RSPs answering questions related to the 'what, 'why', 'where', 'how', and 'who' of scaling up restoration initiatives.<br>\n4. Further dialogue between cases from each cluster will provide inspiration and feedback to work towards a final RSP at the end of the MERLIN project.<br>\n5. The upscaling in the RSPs has a time horizon towards 2050, and recommendations have been made to strengthen this visioning. This long-term visioning should be linked with stepwise implementation, for which the use of adaptive pathway thinking can be used as inspiration.<br>\n6. The term 'restoration' of freshwater ecosystems might put people on the wrong page in the light of changing climate and land use and the time horizon of the RSP. Improving freshwater ecosystems should take these shifting conditions into account to define realistic targets both for biodiversity and delivering ecosystem services.<br>\n7. The formation of multidisciplinary teams that cover the bio-physical, socio-economic and legal/financial aspects of the RSPs is beneficial for the overarching success of the plans. A well embedded monitoring strategy across all these disciplines is needed.<br>\n8. The interim RSPs have been prepared by each case study without interaction with the other case studies. The other interactions are with the financial expertise within MERLIN, the outcomes of the sector roundtables and with the case study board. These interactions will be the main actions to improve the RSPs.<br>\n9. RSPs are designed within the MERLIN project. The implementation of the RSP will be a process to start once the MERLIN project has ended in 2025. During MERLIN, it is essential to define the consortium to adopt and implement the RSP.</p>

Abstract. Data assimilation is the process of combining real-world observations with a modelled geophysical field. The increasing abundance of satellite retrievals of atmospheric trace gases makes chemical data assimilation an increasingly viable method for deriving more accurate analysed fields and initial conditions for air quality forecasts. We implemented a three-dimensional optimal interpolation (OI) scheme to assimilate retrievals of NO2 tropospheric columns from the Ozone Monitoring Instrument into the Danish Eulerian Hemispheric Model (DEHM, version V2009.0), a three-dimensional, regional-scale, offline chemistry-transport model. The background error covariance matrix, B, was estimated based on differences in the NO2 concentration field between paired simulations using different meteorological inputs. Background error correlations were modelled as non-separable, horizontally homogeneous and isotropic. Parameters were estimated for each month and for each hour to allow for seasonal and diurnal patterns in NO2 concentrations. Three experiments were run to compare the effects of observation thinning and the choice of observation errors. Model performance was assessed by comparing the analysed fields to an independent set of observations: ground-based measurements from European air-quality monitoring stations. The analysed NO2 and O3 concentrations were more accurate than those from a reference simulation without assimilation, with increased temporal correlation for both species. Thinning of satellite data and the use of constant observation errors yielded a better balance between the observed increments and the prescribed error covariances, with no appreciable degradation in the surface concentrations due to the observation thinning. Forecasts were also considered and these showed rather limited influence from the initial conditions once the effects of the diurnal cycle are accounted for. The simple OI scheme was effective and computationally feasible in this context, where only a single species was assimilated, adjusting the three-dimensional field for this compound. Limitations of the assimilation scheme are discussed.