A linked meteorological and hydrological model system: the Susquehanna River Basin Experiment (SRBEX)

The goal of the Susquehanna River Basin Experiment (SRBEX) is to simulate the basinʹs hydrologic response to atmospheric forcing at various time scales. To reach this goal, SRBEX concentrates on developing climate downscaling methodologies. One downscaling approach links a high-resolution meteorological model and a suite of coupled hydrological models. This paper (1) provides an overview of this linked model system and its elements, (2) describes a series of simulations and sensitivity experiments, and (3) discusses ongoing model development. In a typical simulation, a nested version of the Penn State-NCAR mesoscale meteorological model (MM5) simulates the precipitation from a storm system passing over the river basin. The resulting high-resolution precipitation field, with grid increments as fine as 4 km, then drives the Hydrological Modeling System (HMS). HMS is composed of physically based, interactive surface routing, groundwater, soil water, and channel leakage components. An important aspect of the system is the application of a geographic information system (GIS) to control the high-resolution soils, land-use, and digital terrain data at the model interface. One significant output from the model system is a simple hydrograph, which represents the integration of basin hydrology over time and space. Experiments have been performed to determine the sensitivity of the linked model system results to the rainfall-runoff abstraction method and to the MM5 nesting scheme. Ongoing research aims at expanding the time scales of analysis, improving model efficiency and speed of computation, and changing the present meteorological–hydrological interaction from a linked system to a coupled system.