An Experimental Daily US Surface Water Monitor 5th International Scientific Conference on GEWEX Orange County, CA June, 2005 An Experimental Daily US Surface Water Monitor Andy W. Wood, Ali S. Akanda, and Dennis P. Lettenmaier Univ. of Washington 2 1 Methods Index Station Method Gridded Forcing Creation OVERVIEW We have implemented an experimental real-time surface water monitoring system that uses the Variable Infiltration Capacity (VIC) macroscale hydrology model (Liang et al., 1994) for real-time estimation of soil moisture, snow water equivalent (SWE) and runoff over the continental U.S. at 1/2 degree spatial resolution. The monitoring system will stage DROUGHT ANALYSIS PRODUCTS, including those described in Andreadis et al. (2005) in real-time, as well as maintain an archive of comparative products extending back to 1915. The monitoring system is driven by daily precipitation & temperature minima and maxima from 2131 Coop stations, and has a 1-day update lag, with updates each day by 2 p.m. PST. The system will also stage weekly outlooks based on similar methods to the ensemble forecasting techniques used in the UW west-wide seasonal hydrologic forecast system. Index Station Forcing Approach Real-time Nowcasting Information Flow VIC Hydrologic Model (Liang et al., 1994) NOAA ACIS Prcp Tmax Tmin Coop Stations A primary goal of this system was to ensure consistency between real-time and retrospective outputs, hence the input stations were limited to those with BOTH reliable real-time reporting and historical records extending back at least 40 years. Because this results in many fewer stations than are available with less stringent criteria, we use the input stations indirectly. First, we estimate precipitation percentile (for ~month long periods) and (daily) temperature anomalies and interpolate them to a 1/8 degree grid. Then we extract corresponding values from a 1/8 degree climatological forcing PDF created using a larger set of station inputs (e.g., not all reporting in real-time, taken from the Andreadis et al. effort described in an associated poster). Finally, temporal disaggregation of the precipitation period values is needed. Currently, the PDF is based on 1915-2003; however, this choice may be revisited. NOAA ACIS Prcp Tmax Tmin Coop Stations 1930s 1955+ Nowcast produced with 1-2 day lag from current Index Meth. VIC Retrospective Simulation Daily, 1915 to Near Current Hydrologic State VIC Real-time Simulation (~1 month long) Hydrologic State (-1 Day) Hydrologic values, anomalies, percentiles w.r.t. retrospective PDF vals, anoms %-iles w.r.t. PDF climatology (PDF) of hydrologic values w.r.t. defined period 3 5 Comparison with Other Datasets Surface Water Monitoring System Products CPC UW Examples of Current Products From a qualitative standpoint, we find good agreement with current real-time CPC soil moisture monitoring tool (recent plots shown at right) CHANGES IN CURRENT CONDITIONS ARCHIVES March 2002: Virginia experiences severe drought, many well failures March 1997: La Nina conditions bring the highest recorded snowfall to the PNW July 2002: the western U.S. drought centers on Colorado August 1993: the highest recorded flow on the Mississippi R. The change in conditions over the past week, 2 weeks and 1 month help to characterize the evolving water balance. Colorado Cell (39.25, -108.25) Andreadis et al. SW Monitor Andreadis et al. The Andreadis et al. retrospective soil moisture dataset shows good spatial and temporal consistency with the SW Monitor simulations (temporal comparison, left) (spatial comparison, right) Current Products (cont.) In Development COUNTY BLOW-UPS TIMESERIES ANAYSIS FOR PIXELS OR REGIONS Clicking the main maps launches blow-up views of parts of the country showing the county delineations. Plots of current hydro-climatic conditions contrasted with other water years and with the daily climatological PDF. 4 Current WEBSITE: http://www.hydro.washington.edu/forecast/monitor/ The “first-cut” implementation of the system has a limited set of products – the primary results shown currently are nowcasts (with a 1-2 day lag depending on time of day) of soil moisture and snow water equivalent percentiles. Other products are in development (see Section 5 at right). 1915-2003 climatology period (PDF) OUTLOOKS Weekly outlooks based on similar methods to those used in the UW west-wide seasonal hydrologic forecast system (using CPC, CFS, NSIPP and ESP climate ensembles). (At right are shown a sample ESP 3-month outlook initialized Febr. 1) In addition to soil moisture, current SWE and (soon) runoff percentiles Images with alternate scale bars (e.g., that match the Drough Monitor categories) are also provided Recent trends in relative soil moisture, SWE, runoff An archive from 1915-present of soil moisture and SWE percentiles on Day 1 of each month, with a simple interface for navigation Other Changes / Ongoing Work References / Acknowledgements improving spatial resolution of the overall monitoring system to 1/8 degree. completing the automation of the nowcast / real-time simulation / plot generations incorporating additional products (beyond percentiles), including runoff maps, cumulative departures from normal, and recovery probabilities (derived from the outlook products) explore different PDF periods and station datasets. (It may be better to screen out more stations to achieve greater consistency with the pre-1950 record). Andreadis, K.M., E.A. Clark, A.W. Wood, A.F. Hamlet, and D.P. Lettenmaier, 2004, 20th Century Drought in the Conterminous United States , Journal of Hydrometeorology (accepted). 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, J. Geophys. Res., 99(D7). The authors acknowledge the support of NOAA/OGP and the NASA Seasonal-to-Interannual Prediction Project (NSIPP).