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05-05-2014: The application now includes watersheds and new water-balance variables (snow water equivalent, runoff, soil water storage and evaporative deficit)

Example of the NCCV
Worldwide climate modeling centers participating in the 5th Climate Model Intercomparison Program (CMIP5) are providing climate information for the ongoing Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change (IPCC). The output from the CMIP5 models is typically provided on grids of ~1 to 3 degrees in latitude and longitude (roughly 80 to 230 km at 45 latitude). To derive higher resolution data for regional climate change assessments, NASA applied a statistical technique to downscale maximum and minimum air temperature and precipitation from 33 of the CMIP5 climate models to a very fine, 800-m grid over the continental United States (CONUS). The full NEX-DCP30 dataset covers the historical period (1950-2005) and 21st century (2006-2099) under four Representative Concentration Pathways (RCP) emission scenarios developed for AR5.

The USGS National Climate Change Viewer (NCCV) includes the historical and future climate projections from 30 of the downscaled models for two of the RCP emission scenarios, RCP4.5 and RCP8.5. RCP4.5 is one of the possible emissions scenarios in which atmospheric GHG concentrations are stabilized so as not to exceed a radiative equivalent of 4.5 Wm-2 after 2100, about 650 ppm CO2 equivalent. RCP8.5 is the most aggressive emissions scenario in which GHGs continue to rise unchecked through the end of the century leading to an equivalent radiative forcing of 8.5 Wm-2, about 1370 ppm CO2 equivalent. To create a manageable number of permutations for the viewer, we averaged the climate and water balance data into four climatology periods: 1950-2005, 2025-2049, 2050-2074, and 2075-2099.

We have used the air temperature and precipitation data from the 30 CMIP5 models as input to a simple water-balance model to simulate changes in the surface water balance over the historical and future time periods on the 800-m CONUS grid. Combining the climate data with the water balance data in the NCCV provides further insights into the potential for climate-driven change in water resources.

The NCCV allows users to visualize projected changes in climate (maximum and minimum air temperature and precipitation) and the water balance (snow water equivalent, runoff, soil water storage and evaporative deficit) for any state, county and USGS Hydrologic Units (HUC). USGS HUCs are hierarchical units associated with watersheds and analogous to states and counties that span multistate areas such as the California Region and telescope down in area to subregions such as the California-Northern Klamath-Costal HUC4, and HUC8 subbasins such as Upper Klamath Lake, Oregon. The viewer provides a number of useful tools for characterizing climate change including maps, climographs (plots of monthly averages), histograms that show the distribution or spread of the model simulations, monthly time series spanning 1950-2099, and tables that summarize changes in the quantiles (median and extremes) of the variables. The application also provides access to comprehensive, summary reports in PDF format and CSV files of the temperature and precipitation data for each geographic area.

Users interested in the water balance variables should consult the tutorial for a discussion of the model and the limitations in this application.

A detailed description of the application and its use can be found in the NCCV Tutorial (PDF).

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Page Last Modified: Tuesday, May 06, 2014