1. 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 ; 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, )
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:
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).
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, 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).