SHiELD-LM4: Coupled Land-Atmosphere Modeling

Fri, 04 Sep 2026 00:00:00 +0000

What I developed

Implicit land-atmosphere coupling between SHiELD and LM4
Integration of the LM4 land component into the SHiELD framework
FMS coupling and exchange-grid infrastructure for conservative water and energy fluxes
High-resolution coupled hydrological simulations
The Hurricane Helene (2024) case study evaluating hydrological extremes

Motivation

Land-atmosphere interactions drive weather and climate extremes. This system integrates advanced atmospheric and land processes to capture how soil moisture, vegetation, and runoff feedback on regional weather patterns, advancing forecast skill for hydrological extremes.

Overview

We present a new high-resolution coupled atmosphere-land model, SHiELD-LM4, which integrates GFDL’s advanced atmospheric model (SHiELD) with the Geophysical Fluid Dynamics Laboratory Land Model (LM4) through the Flexible Modeling System (FMS) coupler. This coupled system enables accurate representation of land-atmosphere interactions, including soil moisture feedbacks, runoff generation, and hydrological extremes.

The model captures critical processes such as precipitation-driven runoff, soil water dynamics, and their impacts on atmospheric evolution during extreme weather events. High-resolution representation is essential for resolving the complex interactions between atmospheric convection and land surface hydrology.

Coupling Infrastructure

The SHiELD-LM4 model employs the Flexible Modeling System (FMS) coupler to facilitate bidirectional exchange between the atmospheric and land components. The exchange grid ensures accurate conservation of water and energy fluxes at the atmosphere-land interface.

Schematic of atmosphere (Atm), exchange grid (Xgrid), and land/ice components showing multi-level coupling infrastructure and flux exchange pathways.

Hurricane Helene (2024): Precipitation and Runoff

A key application of the coupled SHiELD-LM4 system is realistic simulation of extreme precipitation and its hydrological consequences during tropical cyclones. The animation below shows global precipitation and runoff during Hurricane Helene’s landfall, zoomed on the southeastern United States to reveal localized hydrological response.

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Global precipitation (mm/hr), surface runoff, and river discharge (kg/m³/s) during Hurricane Helene (2024). Zoomed panels show detailed runoff and river flow in the southeastern U.S. during landfall.

Soil Moisture and Land Surface Response

The coupling captures soil moisture evolution and its feedback to atmospheric conditions. The animation shows soil liquid water content evolution during an extreme precipitation event, with time series of observed vs. modeled soil moisture at multiple locations.

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Time series of soil liquid water content (kg/m³) at multiple observation sites during Hurricane Helene, illustrating the rapid soil water response to extreme precipitation and subsequent drainage.

Soil Column Interactions

The detailed representation of soil-atmosphere interactions is illustrated through the vertical exchange of water and energy between atmospheric columns and land model soil layers.

Time series of soil liquid content (kg/m³) at four observation locations (Asheville, Buncombe; Busick, Yancey; Boone, Watauga; Jefferson, Ashe) showing hourly evolution during extreme precipitation event.

Key Results

Two-way land-atmosphere coupling effectively captures soil moisture-precipitation feedbacks during extreme events.
Runoff generation and river discharge are accurately simulated at high resolution.
Soil water dynamics show realistic response to precipitation forcing with multi-hour memory effects.
The model demonstrates capability to simulate coupled hydro-atmospheric extremes with kilometer-scale detail.

This work extends coupled modeling capabilities to include detailed land surface hydrology, with implications for weather forecasting, hydrological prediction, and climate research.

Reference

Mouallem, J., Malyshev, S., Tan, Z., Shevliakova, E., Gao, K., Harris, L., Benson, R., Cooke, W., Zadeh, N., and Chilutti, L.: Development of a high-resolution coupled SHiELD-MOM6-LM4 – Part 2: Model overview, coupling technique, and evaluation of hydrological extremes during Hurricane Helene, Geoscientific Model Development (accepted), 2026.

Development of a high-resolution coupled SHiELD-MOM6-LM4 – Part 2: Model overview, coupling technique, and evaluation of hydrological extremes during Hurricane Helene

Thu, 27 Aug 2026 00:00:00 +0000

Hydrology | Joseph Mouallem