Merging Models to Simulate Effects of Global Warming on the Western U.S.
Because of their coarse resolution, global climate models (GCMs) do a poor job of accurately simulating climate in regions with highly variable topography, such as the mountainous western U.S. A typical GCM grid point—a snapshot of conditions at a location on Earth—is about as big as Belgium or the state of Maryland, so it comes as little surprise that despite impressive gains in knowledge of global climate change, GCM information from regions with rugged, varied topography is of limited use in expanding scientists’ ability to understand and predict regional Earth system dynamics.
In turn, this inhibits producing accurate, reliable predictions of regional climate change, which are required for adaptation and mitigation strategies. For example, extreme weather events like heavy rainfall or heat waves are projected to become more frequent as climate changes.Because of their coarse resolution, global climate models (GCMs) do a poor job of accurately simulating climate in regions with highly variable topography, such as the mountainous western U.S. The Nested Regional Climate Model will allow fundamental progress in understanding and predicting regional climate variability and change. Warming means that precipitation now occurs more often as rain instead of snow, that snow melts earlier, that runoff and risk of flooding increase in early spring, and risk of drought and wildfire in summer increases as warmer air dries the land. Such events have enormous implications for agriculture, hydrology, water resources, and urban planning, particularly over the intermountain West.
To plan for the impacts of climate change, western U.S. states require improved models and more powerful computers dedicated to climate modeling and prediction. NCAR has a record of world leadership and achievement in advancing knowledge of weather and climate variability and change. In keeping with its core mission, NCAR develops and supports advanced observing facilities, increasingly powerful supercomputing capabilities and related software, valuable research data sets, and widely used state-of-the-science community weather and climate models.
To create a viable model that can handle varied regional topography in global simulations, scientists merged NCAR’s Weather Research and Forecasting (WRF) model with the Community Climate System Model (CCSM). This Nested Regional Climate Model (NRCM) will allow fundamental progress in understanding and predicting regional climate variability and change. In particular, the multiscale capability of the NRCM allows researchers to better understand how regional-scale processes influence global climate.
The increased fidelity of NRCM simulations will also improve decision makers’ local and regional planning efforts. NCAR scientists performed a series of simulations using the NRCM to examine likely changes in future climate and regional weather statistics over the intermountain West. These unique data sets will be of immense interest and utility to many stakeholders, both in the U.S. and internationally.
