andy wood, ted bohn, george thomas, ali akanda, dennis p. lettenmaier university of washington...
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Andy Wood, Ted Bohn, George Thomas, Ali Akanda, Dennis P. Lettenmaier
University of Washington west-wide experimental hydrologic forecast system
OBJECTIVE The forecasting system was created to evaluate the use of distributed
macroscale hydrologic models for hydrologic forecasting, and provide a testbed for assessing the use of climate predictions and data assimilation in a streamflow forecasting context.
OVERVIEW Forecasts are made once monthly, using simulated initial conditions
based on real-time observations of temperature and precipitation.
Experimental hydrologic forecasts are also made using the climate forecast ensembles derived from the NCEP Climate Prediction Center Seasonal Climate Outlooks.
Benchmark hydrologic forecasts are also constructed via the well-known Extended Streamflow Prediction (ESP) method of the U.S. National Weather Service. The ESP forecasts are also categorized to provide ENSO and PDO-conditioned ensembles, which past work has shown can improve seasonal forecast accuracy.
Major Products of Westwide Forecasting System
References / Acknowledgements
Wood, A.W., E.P. Maurer, A. Kumar and D.P. Lettenmaier, 2002. Long Range Experimental Hydrologic Forecasting for the Eastern U.S., JGR, 107(D20).Liang, X., D. P. Lettenmaier, E. F. Wood and S. J. Burges, 1994. A Simple hydrologically Based Model of Land Surface Water and Energy Fluxes for GSMs, JGR., 99(D7). Wood, A.W. and D.P. Lettenmaier, 2006, A testbed for new seasonal hydrologic forecasting approaches in the western U.S., BAMS (accepted).The authors gratefully acknowledge the support of NOAA/OGP (now the Climate Program Office) CDEP and CPPA programs.
Hydrologic Model (Liang et al., 1994)Hydrologic Forecasting Simulations
Forecast Productsstreamflow soil moisture
runoffsnowpack
derived products
model spin-upforecast ensemble(s)
climate forecast
information
climatology ensemble
1-2 years back start of month 0 end of mon 6-12
NCDC met. station obs. up to
2-4 months from
current
LDAS/other real-time
met. forcings for remaining
spin-up
data sources
snow state information
NRCS SNOTEL / Env. Canada ASP observed SWE anomalies are merged with simulated anomalies to adjust the forecasts’ initial hydrologic state, e.g.:
Forecasts from Climate Model Output
Current Activities
re-evaluating the NASA/NOAA NLDAS 1/8 degree forcing product as a potential real-time forcing in Western U.S. automating nowcast / initial condition simulation over the US westward of the Mississippi River adopting selected experimental reservoir system forecasts as routine products comparing nowcasts with retrospective simulations now in progress extending back to 1915 Expanding the set of streamflow forecast points to the Great Basin, Missouri, and upper Rio Grande Rivers
Other Changes / Ongoing Work
Univ. of Washington
Climate ForecastsESP and ESP/ENSO forecasts• VIC model resolution (1/8 degree)• use ensemble of historical 12 month daily
sequences taken from 1960-99• use subsets based on ENSO category
NCEP CPC Official Outlooks
Snow Assimilation
Components of Overall Real-time Forecasting Approach
example obs SWE anomalies
corresponding SWE adjustment
Forecast Web Page
http://www.hydro.washington.edu/forecast/westwide/
Prior evolution of water balance for drainage area of each forecast location
Spatial Forecasts for P, T, SWE, Soil Moisture, Runoff
Current conditions nowcasts for soil moisture / SWE
• derived from Probability of Exceedence seasonal precipitation and temperature forecasts for US climate divisions
• ensembles of precipitation and temperature generated by non-parameteric resampling approach called the Schaake Shuffle
• from NCEP CFS (in re-development)
Westwide overview map of current water supply period volume forecast
This map clicks through to forecast hydrographs at right, and water balance plots above
Collaboration with Operational and Research Groups
Daily Updating Land Surface Nowcast• Now operational for current domain + Missouri R. basin• Next basins: Mexico, Arkansas-Red, Gulf
We are evaluating the benefits of using three separate models to generate forecasts that can be combined via Bayesian model averaging techniques.
Models: • VIC• SAC – Sacramento /
SNOW17 model (NWS)• NOAH – NCEP, OSU,
Army, NWS Hydrology LabTest Case: Salmon R., ID
Retrospective ComparisonsIndividual Models
Bayesian Model Average
Multiple Land Surface Model Ensembles
Monthly Avg FlowMonthly Avg Flow Monthly RMSEMonthly RMSE
Monthly Avg FlowMonthly Avg Flow Monthly RMSEMonthly RMSE
U. Arizona / USBR
forecast study, Lower Colorado
basin
NWS Hydrologic Ensemble Prediction
Experiment(HEPEX)
3TIER Environmental
Forecast Group
NRCS National Water and Climate Center
Forecast Group
NOAA Climate
Prediction Center’s US
Drought Outlook
Miscellaneous:Seattle City
Light,energy traders,
hydropower utilities,
NOAA regional climate offices
UW Puget Sound region flow forecasts
UW Climate Impacts Group
(CIG)Annual Water
Outlook meetings
NOAA National Centers for
Environmental Prediction
(NCEP) testbed activities
Columbia River Inter-tribal Fish
Commission
Klamath R. Basin
Bureau of Reclamation
UCI / California Dept of Water
Resources
WA State Dept of Ecology &
Yakima R. Basin Bureau
of Reclamation
newUS Drought Monitor
Princeton University Hydrologic Forecast System
UW HydrologicForecast and
NowcastSystems