Linked atmosphere-hydrology models at the macroscale

Abstract

Abstract In this paper we discuss numerous aspects of macroscale hydrologie models and their linkage to atmospheric simulations. We discuss spatial and temporal scaling and conclude that the region is the most critical scale for addressing global change issues. Macroscale hydrologie models might reasonably be considered as a hierarchical, nested system of models focusing on the mesoscale. The nested approach requires a GCM, a mesoscale atmospheric model, a soil-vegetation-atmosphere transfer scheme, and surface/subsurface hydrology models, the latter down to hillslope scale in small representative catchments. A hydrologie analysis system manages input/output functions, scientific visualization, model preparation, and execution. The entire system of data, models and computing tools is being developed to distill the facets of global change to the regional level and to explore feedbacks from the land surface to the atmosphere. INTRODUCTION The emerging field of Earth System Science has fostered the development of large-scale, synoptic views of the Earth's hydrology. This capability is particularly important given a growing consensus within the scientific community of imminent and unprecedented change in the Earth's climate. Although the greenhouse effect is considered global in extent, its critical impacts will occur at regional and smaller scales, such as river basins and agricultural zones. The need to plan for possible climatic change creates a profound challenge to our modelling and monitoring capabilities. The development of international programs such as the Global Energy and Water Cycle Experiment (GEWEX) and the International Geosphere-Biosphere Program (IGBP) is in part a recognition of the need to assess, understand and model the response of regions to potential climate change. In this paper we discuss the use of linked models of atmospheric dynamics, surface water balance and riverine transport to assess regional water resources in the context of global change. The paper has three goals. The first is to develop an operational