The NOAA Rapid Update Cycle (RUC) 1-h assimilation cycle

WWRP Symposium -- Nowcasting & Very Short Range Forecasting – 8 Sept 2005 – Toulouse, France

Stan BenjaminSteve WeygandtJohn Brown

NOAAForecast Systems Lab – Boulder CO, USA

RUC web site - http://ruc.fsl.noaa.gov

GOAL:

• Provide high-frequency (1h) mesoscale 3-d analyses and short-range (1-12+h) forecasts for aviation, severe weather, hydrology, …

RUC Hourly Assimilation Cycle

11 12 13 14 15 16 Time (UTC)

1-hrfcst

Background

Fields

Analysis

Fields

1-hrfcst

1-hrfcst

3DVAR

Obs

1-hrfcst

3DVAR

Obs

3DVAR

Obs

3DVAR

Obs

3DVAR

Obs

1-hrfcst

1-hrfcst

RUC Hourly Assimilation Cycle + Forecasts > 1h

11 12 13 14 15 16 Time (UTC)

9-hrfcst

Background

Fields

Analysis

Fields

9-hrfcst

9-hrfcst

3DVAR

Obs

9-hrfcst

12-hfcst

12-hfcst

3DVAR

Obs

3DVAR

Obs

3DVAR

Obs

3DVAR

Obs

Run-time at NCEP for RUC 12h fcst – 17 min

Data type ~ Number Frequency

Rawinsonde ~85 /12h+spec

Aircraft 1600-6000 /1h

NOAA profiler 32 /1h

VAD winds ~125 /1h

PBL profilers 25 /1h

Surface METAR 1600-1800 /1h

Mesonet ~6000 /1h

Buoy/ship 100-1500 /1h

GOES precip water 1500-3000 /1h

SSM/I precip water 1000-4000 /6h

GPS precip water ~280 /1h

GOES cloud-drift wind 1000-2500 /1h

GOES cloud-top (p,T) ~10km /1h

Radar ref / /lightning 1km13km /1h

RUCObsSources

- experimental13km RUC-- As of 6 Sept 05

5

RUC20Wind forecastAccuracy

-Sept-Dec2002

Verification against rawinsonde data over RUC domainRMS vector difference (forecast vs. obs)

RUC is able to use recent obs to improve forecast skill down to 1-h projection for winds

6 8 10 12 (kts)

1 3 6 912

Analysis~ ‘truth’

6

Application of Digital Filter Initialization (DFI) in RUC Model

• Critical for 1-h assimilation cycle• 45 min forward, 45 min backward – no physics• Average over DFI period• Applicable for diabatic application, nudging to radar obs during DFI ‘pre-forecast’

Noise in surface presat 1h forecast is much lower with DFI

7

Vert Coord Hybrid isentropic-sigma – 50 levels

Stable clouds, NCAR mixed-phase (cloud Precipitation water, rain water, snow,

graupel, ice, ice particle number. concen.

Sub-grid Grell-Devenyi ens schemeprecipitation (144 members, closure/CIN

Land-surface RUC LSM - 6-level soil/veg

model, 2-layer snow model

- Smirnova

Rapid Update Cycle Model

Current operational RUC: 13-km

9-12-hrfcst

Recent changes to RUC13 3DVAR analysis(among many):

1. Use of surface obs throughout PBL (NCEP Fall 2004)

2. Cloud analysis (GOES, METAR ceiling/vis/curr-wx)

9

PBL-based METAR assimilation -- create additional obs corrections thru PBLUse METAR data through PBL depth from 1h fcst

RUC oper analysis18z 3 Apr 02IAD

x xxx

Effect of PBL-basedMETAR assimilation

10

RUC enhancements:

1. Use of METAR obs throughboundary-layer depth (Sept 04)

2. Assimilation of GPS precipitable

water observations (RUC13 - ~Jun05)

CAPE impact from two RUC enhancements

3h fcst WITHenhancements

3h fcstOPERATIONAL

0000 UTC 21 Apr 2004

Severe reports

NWS SPCNorman, OK

Tornadoes

11

Use GOES CTP, radar reflectivity, lightning, METAR (clouds,wx,vis) to modify 1h fcst 3-d q* fields

• Clear/build (change qc, qi, qv) with logical arrays

• Safeguards for pressure-level assignment problems

(marine stratus, convective clouds)

• Use nationwide mosaic radar data to modify water

vapor, hydrometeor fields – in testing, crude

• Lightning data used as a proxy for radar reflectivity

• Feedback to cumulus parameterization scheme – bypass convective inhibition via radar/lightning, GOES ECA

RUC Cloud Analysis

12

GOES cloud top

pressureRadar/lightning data

100

200

300

400

500

600

700

800

900

999

PRES

Qv

Qc

RH

Cloudwater, water vapor and relative humidity before ( )and after (----) GOES Cloud-top pressure adjustment

Rainwater, snow, cloud ice and reflectivity before ( ) and after (----) GOES radar/lightning adjustment

100

200

300

400

500

600

700

800

900

999

PRES

Qr

Qs

QidBZ

13

IFRLIFR VFR CLR MVFR

Sample ceiling analysis impact

Ceiling from RUC hydrometeors

AnalysisWITH

cld/wx/vis obs

AnalysisNO

cld/wx/vis obs

Aviation Flight Rules

cloud ceiling height (meters)

1800 UTC 17 Nov 2003

Observations

Data type ~ Number3-d reflectivity data NSSL mosaicked

data

NASA Langley experimental GOES cloud products

TAMDAR aircraft regional carriers – T/V/RH – lower-mid troposphere

65 aircraft

Radar radial wind 120 WSR-88D radars

GPS zenith wet delay(replacing prec water retrievals)

280, increasing

QC’d mesonet data 6000, but many not usable due to poor siting and lack of QC monitoring/metadata

Experimental or future RUC ObsSources

To be added in next 6 months to experimental13km RUC

15

Radar reflectivity assimilation - experimental RUC13 init 09z - 3-6h precipValid 12-15 UTC 6 Sept 2005

Control – oper RUC

Exp RUC13W/ rad ref assim

Obs – 1345 UTC

Sample 3DVAR analysis with radial velocity

500 mb Height/Vorticity

*Amarillo, TX

DodgeCity, KS

*

*

AnalysisWITHradial

velocity

**

Cint =2 m/s

**

Cint =1 m/s

K = 15wind

Vectors

and speed

0800 UTC 10 Nov 2004

Dodge City, KS

Vr

Amarillo, TX

Vr

*

*

Analysisdifference

(WITH radial

velocity minus

without)

17

 

Current RUC CONUS domain

Planned Rapid Refresh domain

Goals:Hourly NWP update in

- Alaska- Wider E. Pacific-- Canada- Caribbean Sea

Rapid Refresh-replace RUC – 2007-08- 13km resolution - use WRF model

18

The RUC by 2008, testing in 2006

• “Rapid Refresh”• Simple more complex assimilation of radar reflectivity and radial winds• Improved use of sat data, GPS, aircraft, surface/mesonet• Use of WRF model w/ RUC-like physics• Use of NCEP data assimilation (GSI) with RUC-specific enhancements – use of sfc data, cloud analysis• North American coverage