1. HYDROLOGIC APPLICATIONS AT THE UNIVERSITY OF WASHINGTON
Dennis P. Lettenmaier
Department of Civil and Environmental Engineering
CDEP/ARCS Council
State College, PA
October 25, 2005

2. UW ARCS Activity Part of Center for Study of the Earth System
Joint CDEP/ARCS and RISA support (merger of former Hayes Center with Climate Impacts Group
ARCS activity now oriented toward support of science interface of CIG
CIG has both climate change and climate information transfer (S/I) aspects
One activity (formerly under ARCS flex funding) was development of (experimental) Westwide Seasonal Hydrologic Forecast System

3. Brief review of Westwide forecast system
National Surface Water Monitor

4. Background: UW west-wide system
where did it come from?
1997 COE Ohio R. basin/NCEP ->
-> UW East Coast 2000 (NCEP/ENSO) ->
-> UW PNW > UW west-wide 2003
what are its objectives?
evaluate climate forecasts in hydrologic applications
seasonal: CPC, climate model, index-based (e.g., SOI, PDO)
16-day: NCEP EMC Global Forecast System (GFS)
evaluate assimilation strategies
MODIS snow covered area; AMSR-E SWE
SNOTEL/ASP SWE
evaluate basic questions about predictability
evaluate hydrologic modeling questions
role of calibration, attribution of errors, multiple-model use
evaluate downscaling approaches
what are its components?

5. Background: UW west-wide system
NCDC met. station obs. up to 2-4 months from current
local scale (1/8 degree) weather inputs
soil moisture
snowpack
Hydrologic model spin up
SNOTEL Update
streamflow, soil moisture,
snow water equivalent, runoff
Now
1-2 years back
LDAS/other real-time met. forcings for spin-up gap
Hydrologic forecast simulation
Month
INITIAL STATE
SNOTEL
/ MODIS*
Update
ensemble forecasts
ESP traces (40)
CPC-based outlook (13)
NCEP CFS ensemble (20)
NSIPP ensemble (9)
* experimental, not yet in real-time product

6. Background: UW west-wide system
Snowpack
Initial Condition
Soil Moisture
Initial Condition

7. MAP LINKS TO FLOW FORECASTS
monthly
hydrographs

8. Expansion to multiple-model framework
Seasonal Climate Forecast Data Sources
CCA
NOAA
CAS
OCN
CPC Official Outlooks
SMLR CA
Coupled Forecast System CFS
VIC Hydrology Model
NASA
NSIPP/GMAO dynamical model
ESP
ENSO UW
ENSO/PDO

9. LDAS Models
An LDAS intercomparison conclusion: Model results, using default parameters, have a wide spread for some states and fluxes. Every model is doing something better than other models in some parts of the country
NOAH
VIC
MOSAIC
SAC
Dag Lohmann, HEPEX

10. Multi-model framework
Multiple Hydrologic Models
Schaake Shuffle
(Clark et al)
CCA
NOAA
CAS
OCN
CPC Official Outlooks
NWS
SAC
SMLR CA
Wood et al., 2002
Coupled Forecast System (CFS)
VIC Hydrology Model
NASA
NSIPP-1 dynamical model
NOAH LSM
NWS: Day et al;
Twedt et al
ESP
Hamlet et al.,
Werner et al.
weightings calibrated via retrospective analysis
ENSO UW
ENSO/PDO

11. Test Case Salmon River basin upstream of Whitebird, ID

12. Individual model results

13. Individual model results
Monthly Avg Flow
Monthly RMSE

14. Individual model results
VIC appears to be best “overall”
Captures base flow, timing of peak flow
Lowest RMSE except for June
Magnitude of peak flow a little low
SAC is second “overall”
No base flow
peak flow is early but magnitude is close to observed*
NOAH is last
peak flow is 1-2 months early and far too small (high evaporation)

15. RESEARCH -- RESEARCH -- RESEARCH
Ongoing work
RESEARCH -- RESEARCH -- RESEARCH
assimilation of MODIS & other remote sensing
climate forecast (CPC outlooks, climate model, index-based)
downscaling
shorter term forecasts (GFS-based)
multiple-model exploration
further development of SW Monitor
generally, water / energy balance questions in face of climate change / variability
HEPEX support

16. SW Monitor Background
directly related to retrospective drought reconstruction Andreadis et al. (“Twentieth Century drought in the conterminous U.S., JHM, Dec. 2005) and westwide forecast system
enabled by recent NCDC extension of digital data archives back to 1915
makes use of real-time forcing creation methods from the west-wide forecast system
will be used as platform for drought and hydrologic variability analyses in real-time
forecasts that can be used in drought outlook type analysis

17. Monitor Webpage daily updates 1-2 day lag soil moisture & SWE
percentiles
½ degree
resolution
archive from
1915-current
uses ~2130
index stns

19. SW Monitor Information Flow
Index Station Method Gridded Forcing Creation
SW Monitor Information Flow
NOAA ACIS
Prcp Tmax Tmin
Coop Stations
1930s
1955+
VIC Retrospective Simulation
Daily, 1915 to Near Current
Hydrologic
State
VIC Real-time
Simulation
(~1 month long)
Hydrologic
State
(-1 Day)
Hydrologic values,
anom’s, %-iles w.r.t.
retrospective PDF
climatology (PDF) of
hydrologic values
w.r.t. defined period
vals, anoms
%-iles
w.r.t. PDF

20. Future Research Real-time applications!
Drought recovery probability described by soil moisture percentiles: (a) Current drought area (based on August 1933); and for different lead times, maps showing the probability (in each grid cell experiencing drought) that soil moisture percentiles will recover. (b) The grid cell-specific recovery probabilities are derived from real-time soil moisture simulations up to the current date, after which simulations are driven by ensemble climate forecasts based on a variety of sources -- e.g., ESP, climate index-conditioned ESP, and the CPC seasonal climate outlooks

21. Examples of UW (SW Monitor / Forecast System) Interactions with Operational Groups
soil moisture estimates have featured in US Drought Monitor panel/author discussions during Drought Monitor map synthesis.
NRCS National Water and Climate Center (NWCC) has requested UW spatial hydrologic mapping data for the upcoming forecast season.
UW recently demonstrated alternate web-based interface for NWCC forecasts
UW Forecast system approaches to enter into comparative analyses with Colorado RFC forecasts (K. Werner) and with NWCC forecasts (T. Pagano).
UW forecasts in Colorado R. basin were supplied to NWCC for forecast coordination discussions with RFCs last winter (one UW forecast used directly)
UW forecast system spatial maps used in pre-forecast discussions with NWCC forecasters