Web services are a way to utilize scattered resources, collect and deliver information, and manage transactions across computing networks that may be distributed, heterogeneous, and vast. They offer effortless access; anyone who reads a blog or makes a purchase on the internet relies on web protocols. Traditional high performance computing, on the other hand, typically requires highly trained users, who run arcane code on masses of tightly interconnected processors behind firewalls. The NESII team saw an opportunity to extend ESMF in order to bridge the gap between these worlds, and address an emerging issue relevant to NOAA and other agencies: how to integrate projections from high performance climate models with the local tools used by practitioners of water management.
Changes in the water cycle are expected to have impacts on, for example, public health, agriculture, energy generation, and ecosystem services. The integration of information from climate model projections with the tools used by practitioners of water management is a core interest of those developing strategies for adaptation to climate change.
The traditional method of coupling climate and hydrological models is to provide the atmospheric parameters that serve as the inputs for the hydrological model from the archived output of climate models. Another possibility (and the one we focus on) is more realistic: set up a two-way coupling so that feedbacks between the hydrological model and global climate system are possible.
The scientific and software development challenges of either form of coupling are great. The multiple temporal and spatial scales provide an intrinsic challenge. For a hydrological model used in agricultural decision-making, intrinsic scales include the drainage of the streams, the specifics of the land and vegetation in the watershed, surface topography at accuracies of less than a meter, and the surface type of the built environment. Even with the highest resolution climate models likely be viable in the next five years, grid cells on the order of 100 km^2, there are several orders of magnitude difference in the spatial scales. Transference of information in a physically meaningful way across these scales, large-to-small and small-to-large, is neither scientifically nor algorithmically established.
The pilot project, which performs a two-way coupling between a climate and hydrological system, looks forward several years. This type of coupling might be viewed as a logical ideal end state of linking climate models to real-world applications. Rather than waiting until the climate models are at some undefined state of readiness to start the coupling, then starting to develop the coupling strategies, in this pilot we are co-developing the coupling with the model. This will help to define both the scientific foundation of the coupling and evolve the algorithms in concert with the scientific investigation.
ESMF web services is being developed by the NOAA Environmental Software Infrastructure and Interoperability Group (NESII).