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Framework GCOAST

Graphic of modular model system GCOAST

Modular model system GCOAST (Graphic: Ha Hagemann / Hereon)

Framework GCOAST (Geesthacht Coupled cOAstal model SysTem)

The GCOAST (Geesthacht Coupled cOAstal model SysTem) is built upon a flexible and comprehensive coupled model system integrating the most important key components of the regional and coastal systems and, additionally, allowing to include information from observations. In total it encompasses three major model pathways:

Triggered by the need for novel modelling capacity, the GCOAST system is designed to handle cross compartment fluxes of water and energy between the atmosphere and ocean through the dynamic wave interface, dynamics and biogeochemistry in the land ocean transition and marine ecosystems and benthic-pelagic coupling, transport and transformation of environmental pollutants.

GCOAST in applications

Wiese et al. (2019) studied the effects of the coupled COSMO-CLM/WAM models on the atmospheric planetary boundary layer. The improved prediction of wave height and surface winds by applying a coupled atmosphere/wave model was shown by Wahle et al. (2017). It has been demonstrated that coupling between waves and ocean models increase the sea level in the coastal areas (Staneva et al., 2017, Ponte et al., 2019), changes sea temperature and salinity (Alari et al., 2016, Schollen et al., 2017, Staneva et al., 2018), mixing and ocean circulation (Staneva et al., 2017), upwelling (Wu et al., 2019), leading to better agreement with in-situ and satellite measurements (Staneva et al., 2017, Cavaleri et al., 2018; Staneva et al., 2019).

Comparisons with available atmospheric and oceanic observations also showed that the use of the coupled system reduces the prediction errors in the coastal ocean especially under severe storm conditions (Mey-Frémaux et al., 2019, Staneva et al., 2019, Lewis et al., 2019) and is of crucial importance for drifter simulations (Staneva et al., 2018). The internal model variability is pronouncedly reduced during extreme events such as heavy storms when coupling atmosphere, hydrology, ocean and sea ice models (Ho-Hagemann et al., 2020) or when coupling atmosphere and wave models (Wiese et al., 2020).

In a study on biogeochemical processes in the Elbe estuary, Pein et al. (2019) demonstrated the systems capacity to simulate processes in a coupled hydrosphere-biosphere modeling framework. Multi-model couplings developed by Lemmen et al. (2018) have been, e.g., applied for assessing ecosystem impacts of offshore wind farms (Slavik et al. 2019).

GCOAST is a modular system of different models each developed for a specific earth system compartment. Based upon a specific scientific question different models from GCOAST can be selected for use. These models can be plugged together by couplers (OASIS3-MCT, ESMF, FABM) at different levels of coupling granularity, which handle the exchange of information between model combinations, individual models, and processes.

GCOAST combines the efforts of a number of working groups at the institutes within the Helmholtz Research Field Earth and Environment. The groups from the Institute of Coastal Systems develop and apply different GCOAST model components for their scientific research.

GCOAST Components

(Graphic: Ha Hagemann / Hereon)

The group “Regional Land and Atmosphere Modeling” uses and develops the regional atmospheric models COSMO-CLM and ICON-CLM which include already a component for Land/Surface/Soil and Lakes, and the hydrological discharge model HD.

The group “Hydrodynamics and Data Assimilation” contributes to the ocean models NEMO and SCHISM, wave model WAM, WWM and drifter models.

The group “Ecosystem Modeling” develops and applies multi-level coupling infrastructure through ESMF and FABM, ecological models for suspended matter, the pelagic and benthic domains (MAECS, MSPEC) and the sea floor OMEXDIA for near-shore and estuarine research.

The group “Matter Transport and Ecosystem Dynamics” utilizes and develops the ecosystem model ECOSMO, the ocean-biogeochemistry model ICON-COAST as well as models for marine chemistry and benthic processes.

The group "Sediment Transport and Morphodynamics" utilizes SCHISM to investigate sediment transport and morphodynamics, and coupled ECOSMO-TOCMAIM to estimate the impact of benthic biota on early diagenesis of particulate organic carbon (POC).

The group “Chemistry Transport Modeling” of the Institute of Coastal Environmental Chemistry uses and develops the models CMAQ, HiMEMO and UNDYNE for atmospheric chemistry transport processes.