The two-year COMPASS-GLM pilot study aims to enhance predictive understanding of freshwater coastal systems, especially how they respond to climate warming, Land Use Land Cover Change (LULCC), and other perturbations at watershed-to-regional scales. This includes local climate and weather feedbacks that affect wintertime lake effect snows and summertime convective storms.

Figure 1: A schematic of key processes in the Great Lakes Region (from Sharma et al. 2018). The lakes influence,
and are influenced by, many different processes that affect regional ecosystems and human activities.

During the pilot study, modeling activities will focus on two tasks: regional modeling of the Great Lakes region and watershed modeling in the Portage River watershed.

Task: Regional modeling

The first task is focused on coupled, integrated atmosphere–land–lake regional modeling in the Great Lakes Region (Figure 2, left panel). We will use standard community models typically used for regional coastal studies:

All models will be two-way coupled as indicated in Figure 2 (right panel). We will use this coupled modeling system to understand local feedbacks and predict how these feedbacks will be altered in future climate conditions.

Key scientific questions to be addressed are:

  1. How will lake water balance be affected by precipitation and runoff?
  2. How will changes in physical lake processes drive changes to Great Lakes properties and consequently influence regional climate?
  3. How will summer storms and winter lake-effect snowstorms be influenced by regional warming, surface moisture flux, and other factors?
  4. What is the importance of resolving clouds, lake circulation, thermal structure, and ice coverage for accurately simulating atmosphere-lake interactions?
  5. What are the relative contributions of internal variability, parameters, and parameterizations to uncertainties in our coupled model?

We will also use this modeling system to understand how lake-breezes will alter urban heat stress, convective storms, and flooding around Chicago. We will use a refined, nested WRF grid (~0.25-1km grid spacing), coupled with the FVCOM lake model to investigate how the urban heat island affects convective storms and rainfall in the Chicago area. We will use the RIFT model to predict urban flooding caused by intense convective storms. Changes to urban flooding due to climate change will be based in part on the DEMETER land use/land cover (LULC) change model to predict land use changes in the Chicago area, including both urban and non-urban areas.

Key scientific questions to be addressed are:

  1. How do interactions among lake breezes and urban thermodynamic and dynamic processes affect heat stress, mesoscale and locally driven convective systems, and corresponding flooding risk in coastal urban areas?
  2. How will regional LULCC (including urbanization) and climate warming influence summer heat stress events, storm patterns, and flooding in the Great Lakes Region?

Expected outcomes of the pilot study for Task 1 include:

  • A flexible, integrated, and well-tested WRF+FVCOM modeling system that has multiple land surface, dimensionality, and resolution options will be developed.
  • Model output from multiple scenarios and configurations will be archived and shared with the broader scientific community and can be leveraged by other agencies and groups to inform regional decision-making.
  • Improved understanding of coupled processes and interactions will be used to develop multiple peer-reviewed publications and to inform development of E3SM and other modeling systems.
Figure 2: Integrated regional modeling geospatial domain (left) and structure (right) used in COMPASS-GLM. The boundaries of the five Great Lakes (blue) and their watersheds (red) and shown along with the domain for the WRF regional atmospheric simulations (purple). The modeling system leverages previous work to couple at atmospheric model (WRF), including one of its land models (traditional LSM or WRF-Hydro), with a hydrodynamic lake model (FVCOM) that includes a lake ice model (CICE).

Task: High-resolution watershed modeling

The second task will focus on high-resolution modeling of the Portage River watershed (Figure 3a), the site of the COMPASS-FME Great Lakes field campaign. The modeling will focus on improving and applying the Advanced Terrestrial Simulator (ATS) to simulate both surface and subsurface flow in a physically based (as opposed to a statistical) framework, with comparisons to a variety of other terrestrial models (Figure 3b). An important enhancement to ATS will be to include altered water and nitrogen fluxes from drainage tiles.

Expected outcomes of the pilot study include:

  • State-of-the-art high-resolution capability for modeling agricultural watersheds based on the DOE- developed ATS software.
  • Improved understanding of the relative importance of nutrient removal mechanisms in the Portage River watershed and how those mechanisms will be affected by an intensified hydrological cycle.
  • A demonstrated multifidelity approach that makes mechanistically detailed simulations of nutrient transport and transformation tractable at river-basin scales.
Figure 3a: The portage river watershed (Portage River Watershed Plan, Toledo Metropolitan Area
Council of Governments, 2013,  https://tmacog.org/councils-committees/portage-river-basin)
Figure 3b: This figure depicts the relationships between the numerical models used in
Portage River watershed surface and subsurface hydrology simulations.