real time nowcasting in the western us or why you can’t use nodes c0-2

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!


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: West-wide Forecasting System

Soil MoistureInitial

Condition

SnowpackInitial Condition


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.


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





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 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


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





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)


SW Monitor coding scheme

downloadobs

P, tx, tn

update

force

VIC

Station

Index filesclimatology

Forcings

2 mon

Params

Soil, etc.

output


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


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





3. Mexico (retrospective)739 stations1925-2003Real-Time: EDAS (Eta DAS) daily re-analysis

Outline

Objective





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





future plans

Future Work

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

END

Thank you!

real time nowcasting in the western us or why you can’t use nodes c0-2

Documents

westwide forecasting

plots of west

wide swe databackground

station data

drought severity

us land surfaceinitially

realtime lag

hydrologic state