Transcript Document

Update on West Wide Hydrologic Forecasting at the University of Washington
Dennis P. Lettenmaier, Andrew W. Wood, Ted Bohn, George Thomas
Components of Real-time Forecasting Approach
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.
Hydrologic Forecasting Simulations
start of month 0
1-2 years back
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 wellknown 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.
end of mon 6-12
forecast ensemble(s)
model spin-up
climatology ensemble
Climate Forecasts
Hydrologic Model (Liang et al., 1994)
ESP 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
corresponding SWE
adjustment
NCEP CPC Official Outlooks
data
sources
NCDC
met. station
obs. up to
2-4 months
from
current
LDAS/other
real-time
met. forcings
for
remaining
spin-up
climate
forecast
information
snow state
information
Forecast Products
streamflow
soil moisture
runoff
snowpack
derived products
Snow Assimilation
NRCS SNOTEL / Env. Canada ASP observed SWE
anomalies are merged with simulated anomalies to
adjust the forecasts’ initial hydrologic state, e.g.:
example obs.
SWE anomalies
• 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
Forecasts from Climate Model Output
• from NCEP CFS (in re-development)
Major Products of Westwide Forecasting System
Forecast Web Page
Univ. of Washington
Current Activities
During the last year, forecast system
activities have included:
Current conditions nowcasts for soil moisture / SWE
http://www.hydro.washington.edu/forecast/westwide/
• the continued production of monthly
forecasts
• implementation of automatic calibration
approach
• an expansion of forecast products
• increasing interaction with NOAA groups
(EMC and NWS WRSC)
• a major effort to re-stage the system on a
Linux cluster, including:
• fully automated daily updates, rather than
semi-automated monthly
• development of additional forecast points
in new domain areas
Spatial Forecasts for P, T, SWE, Soil Moisture, Runoff
Collaboration with Operational and Research Groups
Notable interactions with external groups:
• Forecast inter-comparison with RFC and NRCS
• Interaction with NCEP EMC
• Interaction with USBR on lower Colorado R.
Expansion of Nowcast simulation domain
Prior evolution of water balance for
drainage area of each forecast location
• Missouri R. basin
added in August
Nowcasts of WY 2006 showing response to strong
North American monsoon precipitation
• Mexico also added
to daily update
simulations, but a
modified approach is
needed to
accommodate
unreliable forcing
Other Changes / Ongoing Work
West-wide overview
map of current water
supply period volume
forecast
This map clicks through
to forecast hydrographs
at right, and water
balance plots above
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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
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 (in press).
The authors gratefully acknowledge the support of NOAA/OGP (now the Climate Program Office) CDEP and CPPA programs.