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

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

Brief review of Westwide forecast system National Surface Water Monitor

Background: UW west-wide system where did it come from? 1997 COE Ohio R. basin/NCEP -> -> UW East Coast 2000 (NCEP/ENSO) -> -> UW PNW 2001 -> 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?

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 6 - 12 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

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

MAP LINKS TO FLOW FORECASTS monthly hydrographs

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

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

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

Test Case Salmon River basin upstream of Whitebird, ID

Individual model results

Individual model results Monthly Avg Flow Monthly RMSE

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)

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

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

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

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

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

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