Coupled Atmosphere–Biophysics–Hydrology Models for Environmental Modeling

TLDR

LEAF‑2 has been applied in independent studies and shown to agree with observational data. The study links RAMS, LEAF‑2, and TOPMODEL to create a system for investigating how altered climate forcing affects coupled atmosphere–biophysical–hydrologic processes at watershed and basin scales. LEAF‑2, a prognostic land‑surface model within RAMS, represents temperature, soil, snow, vegetation, and canopy air, uses a patch‑based subgrid scheme, and is coupled to a modified TOPMODEL that simulates lateral groundwater transport. Sensitivity experiments reveal that patch representation and lateral water transport significantly influence model behavior in idealized simulations.

Abstract

The formulation and implementation of LEAF-2, the Land Ecosystem–Atmosphere Feedback model, which comprises the representation of land–surface processes in the Regional Atmospheric Modeling System (RAMS), is described. LEAF-2 is a prognostic model for the temperature and water content of soil, snow cover, vegetation, and canopy air, and includes turbulent and radiative exchanges between these components and with the atmosphere. Subdivision of a RAMS surface grid cell into multiple areas of distinct land-use types is allowed, with each subgrid area, or patch, containing its own LEAF-2 model, and each patch interacts with the overlying atmospheric column with a weight proportional to its fractional area in the grid cell. A description is also given of TOPMODEL, a land hydrology model that represents surface and subsurface downslope lateral transport of groundwater. Details of the incorporation of a modified form of TOPMODEL into LEAF-2 are presented. Sensitivity tests of the coupled system are presented that demonstrate the potential importance of the patch representation and of lateral water transport in idealized model simulations. Independent studies that have applied LEAF-2 and verified its performance against observational data are cited. Linkage of RAMS and TOPMODEL through LEAF-2 creates a modeling system that can be used to explore the coupled atmosphere–biophysical–hydrologic response to altered climate forcing at local watershed and regional basin scales.