real time nowcasting in the western us or why you can’t use nodes c0-2
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Real Time Nowcasting In The Western UsOR
Why you can’t use nodes C0-2
George ThomasAndy Wood
Dennis Lettenmaier
Department of Civil and Environmental Engineering
LAND SURFACE HYDROLOGY RESEARCH GROUPGroup 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
Monitor Webpage
dailyupdates
1-2 day lag
soil moisture& SWEpercentiles
½ degreeresolution
archive from1915-current
uses ~2130index stns
Background: UW SW Monitor
trends:1 week2 week1 month
Archive!
Background: UW SW Monitor
Archive from 1915-current
current conditions are a productof the same simulation (samemethods, ~same stations) ashistorical 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
Soil MoistureInitial
Condition
SnowpackInitial Condition
Background: West-wide Forecasting System
NEW: West-wide overview of flow forecasts
(mouse-over/clickablefor more details)
As previously, flow location maps give access to monthly hydrograph plots, and also to data.
Background: West-wide Forecasting System
Now clicking the stream flow forecast map also accesses current basin-averaged conditions
An earlier G. Thomas contribution:
Automating plots of west-wide SWE data
Background
West-wide Forecasting System
Daily UpdatingWest-at-a-glanceSWE fromNRCS, EC, CADWR
Analyses: Current Anomalies Percentiles:
Current1-week change2-week change
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”
# st
atio
ns
time 3 monthsbefore present
present
VIC model spinup methods: index stationsestimating spin-up period inputs
dense station network for model calibration sparse station network in real-time
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
Index stn pcp (mm) pcp
percentile
gridded to 1/8 degree
1/8 degree dense station monthly pcp DISTRIBUTION(N years for each 1/8 degree grid cell)(MM)
1/8 degree pcp (mm) disagg. to
dailyusing interpolated daily fractions from index stations
monthly daily
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 stationmethod
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
VIC Retrospective SimulationDaily, 1915 to Near Current
VIC Real-timeSimulation
(~1 month long)
HydrologicState
NOAA ACIS / OtherPrcp Tmax Tmin
Coop Stations
Index Station Method Gridded Forcing Creation
Hydrologic values, anom’s, %-iles w.r.t.retrospective PDF
climatology (PDF)of
hydrologic valuesw.r.t. defined period
vals, anoms%-iles
w.r.t. PDF
1955+
HydrologicState
(-1 Day)
1930s
Implementation Details
Computing Environment: Flood Cluster 46 cores9 AMD Opteron 2x dual core2 Intel Xeon 2X single core1 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
downloadobs
P, tx, tn
update
force
VIC
Station
Index filesclimatology
Forcings
2 mon
Params
Soil, etc.
output
Implementation Details
SW Monitor coding scheme – NCAST implementation
downloadobs
P, tx, tn
update
force
VIC
Station
Index filesclimatology
Forcings
2 mon
Params
Soil, etc.
output
obs
P, tx, tn
update
force
VIC
output
Forcings
2 mon
Params
Soil, etc.
climatology Station
Index files
Node 0-2 Node 0-6
Loop over basinsca, colo, gbas, riog
Loop over basinspnw, mexn, mexs
Implementation Details
Observation data:Real-time and retrospectivestations.3 Primary sources
Implementation Details
Observation data:Real-time and retrospectivestations.3 Primary sources
1. ACIS for CONUS2123 stations1915-present
Implementation Details
Observation data:Real-time and retrospectivestations.3 Primary sources
1. ACIS for CONUS2123 stations1915-present
2. Environment Canada10 stations1915-present
Implementation Details
Observation data:Real-time and retrospectivestations.3 Primary sources
1. ACIS for CONUS2123 stations1915-present
2. Environment Canada10 stations1915-present
Implementation Details
Observation data:Real-time and retrospectivestations.3 Primary sources
1. ACIS for CONUS2123 stations1915-present
2. Environment Canada10 stations1915-present
3. Mexico (retrospective)739 stations1925-2003
Implementation Details
Observation data:Real-time and retrospectivestations.3 Primary sources
1. ACIS for CONUS2123 stations1915-present
2. Environment Canada10 stations1915-present
3. Mexico (retrospective)739 stations1925-2003Real-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!
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