1. Kostas Andreadis, Dennis Lettenmaier
A System for Real-time Prediction of Hydrological Drought Over the Continental U.S.
Andy Wood
Kostas Andreadis, Dennis Lettenmaier
Dept. of Civil and Environmental Engineering
Land Surface Hydrology Research Group
2007 NOAA CPAS Workshop
Seattle, WA
March 2007

2. drought definition practices are evolving

3. talk outline experimental Surface Water Monitor background
nowcast and retrospective products
forecasting drought
final comments

4. SW Monitor in a nutshell
Background:
merges UW west-wide streamflow forecast system methods with NLDAS modeling advances
“index station” method + VIC implementation (Maurer et al., 2002)
benefits from recent NCDC extension of digital data archives back to 1915
created to illustrate concept from unfunded NCTP05 proposal
Future:
water cycle analysis – current and retrospective
“proving ground” for forecasting / assimilation methods
will be useful for staging real-time products based on other UW drought reconstruction work:
Severity-Area-Duration analysis (Andreadis et al. 2005)
CONUS drought trends (Andreadis and Lettenmaier, 2006)

5. VIC Retrospective Simulation
Index Station Method Gridded Forcing Creation
SW Monitor Schematic
NOAA ACIS
Prcp Tmax Tmin
Coop Stations
1930s
1955+
VIC Retrospective Simulation
Daily, 1915 to Near Current
Hydrologic
State
VIC Real-time
Spinup
Simulation
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

6. www.hydro.washington.edu / forecast / monitor /

7. Surface Water Monitor products
1 month change in soil moisture
2 week change in
SWE

8. Surface Water Monitor archive (1915-current)
June
1934
Aug
1993

9. Drought delineation / S.A.D. index
In each of these figures, the upper panel shows percent severity based on soil moisture. Red is most severe (100%), yellow is less severe (80%). The lower panel shows the classification of distinct drought events, with each color denoting a separate event. The question remains: How can we define a distinct drought event if droughts are continuous in one month, but discontinuous in the next month? Our algorithm identifies droughts at each time step, checks for common pixels between time steps, and groups the cluster with overlapping pixels at the current timestep with that in the last time step. If a drought seperates, as shown here, or merges, each subdrought (distinct) cluster is grouped as a continuation of the single larger drought event. However, in the subsequent steps, each subdrought is treated separately to ensure that only contiguous areas are compared.
Work of Kostas Andreadis and Liz Clark

10. Washington State ‘Monitor’

11. Monitoring and Prediction MethodsWA
State
soil moisture
SWE

12. WA State testbed for experimental indices
Can we develop alternative, model-based descriptors of drought and stage them reliably for use in state & local actions?
NOAA PDSI
smoothed SM %-ile

13. extension of monitoring to Mexico

14. Forecast Products Ensemble Streamflow Prediction (ESP) technique:
combine: (1) estimate of current hydrologic state
(2) forecast of historical climate
produce: streamflow forecast with uncertainty information
CPC Outlook
ICs
Spin-up
Forecast
obs
recently observed
meteorological data
ensemble of met. data
to generate forecast
ESP-type forecast
method
hydrologic
state

15. drought onset / recovery prediction

16. median forecasts Initial soil moisture percentiles 2/2006
1 month lead, forecast for 3/2006
3 month lead, forecast for 5/2006
6 month lead, forecast for 8/2006)
median forecasts

17. Initial Condition

18. One month lead -- observed

19. Three month lead -- observed

20. Six month lead -- observed

21. California-Arizona drought recovery forecast
SAD Index
feb mar apr may jun jul aug

22. Texas drought recovery forecast
SAD Index
feb mar apr may jun jul aug

23. Verification possibilities?
What are the obs for drought?
In football, everything is complicated by the presence of the other team.
Jean-Paul Sartre
modeling
observations.
paraphrasing

24. Final Comment
How will models (land surface / climate / coupled) become integrated into drought management?
“nowcasting”, forecasting?
retrospective diagnosis?
attribution / detection?

25. Acknowledgments NOAA CDEP, CPPA, SARP, (TRACS?) Feedback from:
CPC’s Doug Lecomte
DRI’s Kelly Redmond
SRCC’s Victor Murphy
SRCC/ACIS’s David Sathiaraj
In house:
Ali Akanda, George Thomas
Kostas Andreadis