Real Time Nowcasting In The Western Us OR Why you can’t use nodes C0-2 George Thomas Andy Wood Dennis Lettenmaier Department of Civil and Environmental Engineering LAND SURFACE HYDROLOGY RESEARCH GROUP Group Seminar July 5, 2006

Outline Objective background surface water monitor westwide forecast system challenges index station method for real-time forcing generation implementation details progress / results to date future plans

Objective Monitor the hydrologic state of the US land surface Initially, western US; soon, mexico + remainder of US 1/8 degree Daily updates in real-time (lag of 12-36 hrs) Soil moisture, snow, runoff Fully automated Consistent with retrospective: back to at least 1950 Can be used for hazard assessment Drought Flood risk Can be used to initialize hydrologic forecasts Short lead, 1-15 day Long lead, 1-12 month

Background This nowcast draws upon procedures and data from two existing systems assembled by Dr. Wood UW Experimental Surface Water Monitor (1/2 degree) Methods for real-time forcing generation & model updating UW West-wide Seasonal Hydrologic Forecasting System VIC model data at 1/8 degree Eventually, forecast methods The nowcast will eventually be an integral part of the West-wide forecasting system

SW Monitor Background An outgrowth of the west-wide forecasting system that adds a national scale perspective on land surface moisture directly relevant to retrospective drought reconstruction work going on in our group Andreadis et al. (2005) paper on drought ½ degree VIC input parameters enabled by recent NCDC extension of digital data archives back to 1915 will be used as platform for drought and hydrologic analyses in real-time nowcasts are used now by US Drought Monitor & US Drought Outlook authors (at CPC and elsewhere) many products possible, such as following one:

Drought Severity and Spatial Extent 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.

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

Background: UW SW Monitor trends: 1 week 2 week 1 month Archive!

Background: UW SW Monitor Archive from 1915-current current conditions are a product of the same simulation (same methods, ~same stations) as historical conditions allows comparison of current conditions with historical ones can navigate by month or year People: Andy, Ali, Kaiyuan, Dennis

Background: UW SW Monitor

Background: West-wide Forecasting System Snowpack Initial Condition Here I typically say the system is implemented using VIC (wat/nrg balance model, etc.), and the spinup simulation produces an initial condition for snowpack and soil moisture over a domain of about 18,000 cells. Soil Moisture Initial Condition

Background: West-wide Forecasting System NEW: West-wide overview of flow forecasts (mouse-over/clickable for more details) This bubble plot shows the streamflow outlook for summer runoff for about 90 locations in the domain. The anomalies are consistent with those shown in the spatial plots, with the lowest outlooks for the SW streams nearest that very low SM pattern we saw 2 slides back, and normal outlooks in the PNW. Note, this west-at-a-glance display, with both mouse-overs that show various anomalies for the locations, and clickable points that launch more details, is something we have only recently added.

Background: West-wide Forecasting System As previously, flow location maps give access to monthly hydrograph plots, and also to data. Now clicking the stream flow forecast map also accesses current basin-averaged conditions In addition to the streamflow hydrographs that we’ve had for a while, the clickable streamflow map now brings up the current water year conditions for P,T,SM,SWE, RO – which are helpful in showing where we are with respect to climatology. These are averaged over the drainage basin contributing to streamflow at each location.

Background West-wide Forecasting System Daily Updating West-at-a-glance SWE from NRCS, EC, CADWR Analyses: Current Anomalies Percentiles: Current 1-week change 2-week change An earlier G. Thomas contribution: Automating plots of west-wide SWE data Another new feature is that we’re now plotting up several analyses of snow observations, and these update on a daily basis. We’ve been automatically downloading the data for a long time for use in our assimilation, and the goal here was to show the west-wide conditions at a single glance, something that’s hard to find elsewhere. Note, in addition to the NRCS snotel points, we also have the California DWR snow pillows, and the Env. Canada snow pillows in the Columbia R. drainage. There are about 5 plots – some of which are for changes during the last week or two.

Background: Central Challenge Model simulations are calibrated and validated using a uniform or consistent set of forcing data Nowcasts and forecasts use models calibrated and validated retrospectively Problem: the station data used to create forcings are not as widely available in real-time as they are for the retrospective calibration/validation period Solution: the “index-station method” # stations time 3 months before present present

VIC model spinup methods: index stations estimating spin-up period inputs sparse station network in real-time dense station network for model calibration

Outline Objective background surface water monitor westwide forecast system challenges index station method for real-time forcing generation implementation details progress / results to date future plans

Index station method: example for precipitation uses time-varying precipitation signal ONLY FROM stations that report reliably in real-time and for over 45 years (many go back longer) precipitation percentiles calculated from raw precip for time period no shorter than 21 days. percentiles interpolated to 1/8 degree grid at 1/8 degree, percentiles used to extract corresponding observed value from 1/8 degree restrospective distribution (based on dense observing network, standard VIC forcing methods) period 1/8 degree precip amount disaggregated using the fractional daily precipitation for that period (interpolated to 1/8 degree grid). temperature is treated differently – daily interpolated anomalies for Tmin & Tmax are used

Index station method: example for precipitation monthly daily Index stn pcp (mm) gridded to 1/8 degree pcp percentile 1/8 degree pcp (mm) disagg. to daily using interpolated daily fractions from index stations important point(s): the approach attempts to make use of forecast skill from 2 sources: better understanding of synoptic scale teleconnections and the effects of persistence in SSTs on regional climate, as reproduced in coupled ocean-atmosphere models; the macroscale hydrologic model yields an improved ability to model the persistence in hydrologic states at the regional scale (more compatible with climate model scales than prior hydrologic modeling). Climate forecasts with monthly and seasonal horizons are now operationally available, and if they can be translated to streamflow, then they may be useful for water management. 1/8 degree dense station monthly pcp DISTRIBUTION (N years for each 1/8 degree grid cell) (MM)

Index station method: example for precipitation In real-time, with daily updates, this method actively updates the forcings for a period from 3 weeks to 7 weeks. case 1: current day is less than day 21 of month treated as 1 period for percentile calculation months case 2: current day is greater than day 20 of month treated as 2 periods for percentile calculation the first month becomes fixed in forcing data months

Index station method test of method for streamflow

Outline Objective background surface water monitor westwide forecast system challenges index station method for real-time forcing generation implementation details progress / results to date future plans

Nowcast Information Flow Index Station Method Gridded Forcing Creation Nowcast Information Flow NOAA ACIS / Other 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

Implementation Details Computing Environment: Flood Cluster 46 cores 9 AMD Opteron 2x dual core 2 Intel Xeon 2X single core 1 AMD Opteron 2x single core Rocks 4.0.0 / CentOS 4.0 Linux Nowcasting is implemented on nodes c0-2 and c0-6 Useful phrases: WTF?! (what the flood?!) RTFM!! (read the flood manual)

Implementation Details SW Monitor coding scheme download obs P, tx, tn update Station Index files climatology force Forcings 2 mon Params Soil, etc. VIC output

Implementation Details SW Monitor coding scheme – NCAST implementation Node 0-2 Node 0-6 download obs P, tx, tn obs P, tx, tn update update Station Index files Station Index files climatology climatology Loop over basins ca, colo, gbas, riog Loop over basins pnw, mexn, mexs force force Forcings 2 mon Params Soil, etc. Params Soil, etc. Forcings 2 mon VIC VIC output output

Implementation Details Observation data: Real-time and retrospective stations. 3 Primary sources

Implementation Details Observation data: Real-time and retrospective stations. 3 Primary sources 1. ACIS for CONUS 2123 stations 1915-present

Implementation Details Observation data: Real-time and retrospective stations. 3 Primary sources 1. ACIS for CONUS 2123 stations 1915-present 2. Environment Canada 10 stations

Implementation Details Observation data: Real-time and retrospective stations. 3 Primary sources 1. ACIS for CONUS 2123 stations 1915-present 2. Environment Canada 10 stations

Implementation Details Observation data: Real-time and retrospective stations. 3 Primary sources 1. ACIS for CONUS 2123 stations 1915-present 2. Environment Canada 10 stations 3. Mexico (retrospective) 739 stations 1925-2003

Implementation Details Observation data: Real-time and retrospective stations. 3 Primary sources 1. ACIS for CONUS 2123 stations 1915-present 2. Environment Canada 10 stations 3. Mexico (retrospective) 739 stations 1925-2003 Real-Time: EDAS (Eta DAS) daily re-analysis

Outline Objective background surface water monitor westwide forecast system challenges index station method for real-time forcing generation implementation details progress / results to date future plans

Results daily forecast of SM percentiles

Results daily forecast of SM percentiles – animations of recent forecasts

Results daily forecast of SM percentiles - comparison with SW Monitor

Results daily forecast of SM percentiles - comparison with CPC Drought Monitor

Results daily forecast of SM percentiles - 2 week change - comparison with SW Monitor

Results April 1 SWE Archive (1997 – 2006)

Outline Objective background surface water monitor westwide forecast system challenges index station method for real-time forcing generation implementation details progress / results to date future plans

Future Work Ongoing and Future Work data products expansion (Arkansas, etc.) routing constraints using SWE

END Thank you!