National Climate Change Viewer (NCCV) Updates
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We have published a comprehensive evaluation comparing the hydroclimate projections derived from six statistically downscaled data sets, which includes the data set underpinning the USGS National Climate Change Viewer (NCCV). We use the monthly water balance model from the NCCV to quantify and decompose uncertainties associated with 14 general circulation models (GCMs) and statistical techniques in projections for four snow‐dominated regions in the western United States. The end‐of‐century projections from GCMs exhibit substantial variation in change over the regions (temperature range of 2.8–8.0 °C and precipitation range of −22–31%). The six downscaled data sets exhibit disparate high‐resolution representations of the magnitude and spatial patterns of future temperature (up to 2.2 °C) and precipitation (up to 30%) for a common GCM. Two data sets derived by the same downscaling method (Multivariate Adaptive Constructed Analogs) produce median losses of snow water equivalent over the Upper Colorado of 51% and 81%. The principal causes of the differences among the downscaled projections are related to the gridded observations used to bias correct the historical GCM output. Specifically, (1) whether a fixed atmospheric lapse rate (−6.5 °C/km) or a spatially and temporally varying lapse rate is used to extrapolate lower elevation observations to high‐elevations and (2) whether high‐elevation station data (e.g., SNOTEL) are included in the observations. The GCM projections are the largest source of uncertainty in the monthly water balance model simulations; however, the differences among seasonal projections produced by downscaled data sets in some regions highlight the need for careful evaluation of the statistically downscaled data in climate impact studies.
Our study can be found at: https://doi.org/10.1029/2018WR023458
The supporting data release is at: https://doi.org/10.5066/P9O9EB1CThe statistically downscaled datasets are as follows:
- BCCA: Bias Corrected Constructed Analogs (Reclamation, 2013)
- BCSD-C: Bias Corrected Spatial Disaggregation (Reclamation, 2013)
- BCSD-F: Bias Corrected Spatial Disaggregation (Thrasher et al., 2013) [Data set in the NCCV]
- LOCA: Localized Constructed Analogs (Pierce et al., 2014)
- MACA-L: Multivariate Adaptive Constructed Analogs (Abatzoglou & Brown, 2012, bias corrected by Livneh et al., 2013)
- MACA-M: Multivariate Adaptive Constructed Analogs (Abatzoglou & Brown, 2012, bias corrected by METDATA, Abatzoglou, 2013)
- BCCA, BCSD-C: http://gdo-dcp.ucllnl.org/downscaled_cmip_projections/dcpInterface.html
- BCSD-F: https://cds.nccs.nasa.gov/nex/
- LOCA: http://loca.ucsd.edu/
- MACA-L, MACA-M: http://maca.northwestknowledge.net
The GCMs evaluated are the following: bcc-csm1-1, CanESM2, CNRM-CM5, CSIRO-Mk3-6-0, GFDL-ESM2G, GFDL-ESM2M, inmcm4, IPSL-CM5A-LR, IPSL-CM5A-MR, MIROC-ESM, MIROC-ESM-CHEM, MIROC5, MRI-CGCM3, NorESM1-M
We have completed a major revision to the National Climate Change Viewer that replaces the hydroclimate variables displayed in the application. We have changed the water-balance model parameterizations to improve the performance of the model relative to observations, particularly in the simulation of snow. We include spatially varying soil water holding capacities based on the State Soil Geographic Data Base (STATSGO). We also revised the model to use a potential evapotranspiration calculation more appropriate for the 21st century, which reduces drying relative to our previous dataset. A detailed evaluation of the model can be found at: http://onlinelibrary.wiley.com/doi/10.1002/2016WR018665/full
With the publication of our formal evaluation of the hydroclimate modeling, the hydrology variables (runoff, soil storage, snow and evaporative deficit) are now included in the downloadable CSV files for each region. All the gridded water-balance model data (~14 Tb) are available from the USGS GeoData Portal in the form of monthly time series spanning 1950-2099 for the contiguous United States. The downloadable PDF reports for states, counties and watersheds have been updated to incorporate the new hydroclimate data. The climatology plots within the PDF reports have been modified to include symbols displaying ensemble agreement and significance.Additional changes to the application:
- Climatology period changed from 1950-2005 (bias correction period) to 1981-2010 (current climate normal). The "historical" simulations end at 2005, so RCP4.5 data are used for 2006-2010.
- Precipitation units are now in in/mo or mm/mo.
An error was found in the downloadable CSV files for the HUC2, HUC4 and HUC8 watersheds. The values displayed in the NCCV are correct. All downloadable HUC CSV files were replaced as of 12/9/2015 at 6:00PM PST. Any HUC files downloaded prior to this date should be replaced with the corrected files.
The second major version of the National Climate Change Viewer includes the following key additions and improvements:
- 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. The water-balance model provides new variables for snow water equivalent, runoff, soil water storage and evaporative deficit. See Section 4 in the Tutorial and Documentation for information about the water-balance model.
- In addition to states and counties, the application now includes summaries for watersheds using the USGS Hydrologic Units (HUC2, HUC4, and HUC8).
- The downloadable PDF Summary Reports now include the water-balance variables and have been consolidated into an overarching summary for each geographical unit (state, county or watershed).
- The Tutorial and Documentation has been expanded to include background for the new water-balance model variables and has been reformatted as a downloadable PDF document.
The web application has been updated to provide both English and metric units and includes new map cache techniques to provide faster map generation.
Important Information Regarding Mean Model RCP8.5 Precipitation
Issued 12/13/2013 9:24AM PST
The RCP8.5 mean model precipitation time series plots in the viewer and in the PDF and CSV files have been corrected. The previous plots and data for RCP8.5 precipitation were inadvertently based on averages for all models and both the RCP4.5 and RCP8.5 scenarios. As of 12/13/2013 at 9:45AM PST, the viewer and the CSV files have been updated. The revised PDF summaries for the mean model will be available later today.